Where Our Hydroponic Crop Numbers Come From

⏳ 6 min read · Last reviewed: 24 September 2026

Every growing number on this site, for all 39 crops, is listed on this page next to the sources it was checked against. Where no good source exists, the page says so instead of dressing up a guess. It is the same master crop table the posts, the calculators and the book use, so if a post and this page ever disagree, this page is the one to trust and the post is the one to fix.

🧪 How Every Number Was Checked

Each crop was searched separately, aiming at universities, extension services, peer-reviewed trials and seed catalogues. Up to twelve sources per crop were read in full, PDFs included. Every figure was then read in context: the right crop, the right growth stage, the right unit, and a recommendation rather than one trial’s setting. The search never looked for the site’s own numbers, so sources that disagree were collected as readily as sources that agree.

When good sources disagreed, the site took the narrower, safer range, because a beginner is better served by a safe target than a wide one. When the sources pointed somewhere else, the number was changed. That happened for about fifty numbers in September 2026, including water temperature, sweet basil’s feed and cilantro’s pH.

🏷️ What the labels mean

Sources are ranked by type: University or research (extension services, government and peer-reviewed work), Seed company or maker (technical growing data), Trade press, and Grower or shop guide. Each crop below lists at most three per number, best first, with the figure each one gives.

🌐 The Rules That Apply to Every Crop

A few numbers are set once for the whole site. A crop’s own entry below overrides them where it gives its own figure, spinach’s cooler water being the best-known case.

🌱 Crop by Crop

Tap a crop to open its numbers. New to all this? The complete apartment hydroponics beginner guide shows how the numbers fit together. For using them day to day, the pH and nutrient calculator and the seed to harvest calculator use exactly these figures.

• Arugula
• Bok Choy
• Butterhead Lettuce
• Calendula
• Celery
• Cherry Tomatoes
• Chives
• Cilantro
• Dill
• Dwarf Cucumber
• Dwarf Peppers
• Garlic Chives
• Green Onions
• Kale
• Lemon Balm
• Lemongrass
• Lettuce
• Micro Herbs
• Microgreens
• Mint
• Mizuna
• Mustard Greens
• Nasturtium
• Oregano
• Parsley
• Pea Pods
• Romaine Lettuce
• Rosemary
• Sage
• Shiso / Perilla
• Spinach
• Stevia
• Strawberries
• Sweet Basil
• Swiss Chard
• Tarragon
• Thyme
• Watercress
• Wheatgrass

Arugula

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	USDA-ARS Application Technology Research, Wooster OH: EC effects on hydroponic arugula (NFT) University or research pH 5.8 (one trial’s setting) University of Arkansas, Horticulturae 2023, 9, 486: replenishment solutions for arugula and basil University or research maintained 5.5 to 6.0 (one trial’s setting)
EC, seedling	1.0 to 1.2 House practice	No published source states this figure.
EC, mature	1.4 to 1.8 Partly backed Was 1.2 to 1.6 before September 2026	USDA-ARS Application Technology Research, Wooster OH University or research optimal 1.5 to 1.8 Santos et al. 2022, Irriga 27(3):639-652, hydroponic arugula dilutions University or research maximum fresh mass at 1.77 to 1.88
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	60 to 70°F House practice	No published source states this figure.
Light hours	14 hours on, 10 hours off Partly backed	UMass Extension, Greenhouse Greens Resources University or research very little growth below 10 hours of day length
Light intensity (PPFD)	200 to 300 µmol/m²/s (DLI about 10 to 15) Partly backed Was 200 to 300 µmol/m²/s before September 2026	University of Arkansas, hydroponic arugula and basil nutrient trials (HortScience/ScholarWorks hortpub 1001) University or research DLI 15.8 (expt 1) and 9.38 (expt 2) mol/m²/day
Light height	6 to 8 in House practice	No published source states this figure.
Germination	5 to 7 days Updated to match the sources Was 3 to 5 days before September 2026	Cornell Garden-Based Learning, Vegetable Growing Guides: Arugula University or research 5 to 7 days to emergence Johnny's Selected Seeds, Arugula Key Growing Information Seed company or maker germinates within 5 to 7 days
Spacing	4 to 6 inches between plants Partly backed	UF/IFAS Florida Fresh, Arugula plant detail University or research plant spacing 3 to 4 inches Oregon State University, Oregon Vegetables: Arugula University or research 6 to 9 inches in the row
Plant height	6 to 10 inches Partly backed	UF/IFAS Florida Fresh, Arugula plant detail University or research harvest at 8 to 10 inches tall
Humidity	50 to 70% House practice Was 40 to 70% before September 2026	No published source states this figure.
First harvest	30 to 40 days Backed by sources	Cornell Garden-Based Learning, Arugula growing guide University or research as early as 4 weeks after seeding USDA-ARS Application Technology Research, Wooster OH University or research harvested 28 days after transplanting

Bok Choy

Number	What the site says	Sources checked
pH	6.0 to 7.0 Partly backed Was 6.0 to 6.5 before September 2026	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research pH 7 UF/IFAS HS1337, Bok Choy, an Asian Leafy Green Vegetable Emerging in Florida University or research 5.5 to 7.0 (soil growing)
EC, seedling	1.0 to 1.2 Partly backed	Rise Gardens, Complete Guide to Hydroponic Bok Choy Growing Grower or shop guide 0.8 to 1.0 at germination
EC, mature	1.5 to 2.0 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 1.5 to 2.0 IGWorks, Growing Hydroponic Bok Choy Grower or shop guide 1.5 to 2.0; higher speeds bolting
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Lanitex Hydro Garden, Grow Bok Choy (Australia) Grower or shop guide 18 to 24°C
Air temperature	60 to 70°F Backed by sources	UF/IFAS HS1337, Bok Choy, an Asian Leafy Green Vegetable Emerging in Florida University or research 64 to 68°F best Rise Gardens, Complete Guide to Hydroponic Bok Choy Growing Grower or shop guide 60 to 75°F; above 80°F bolts
Light hours	14 hours on, 10 hours off Partly backed	Rise Gardens, Growing Bok Choy Hydroponically Grower or shop guide 12 to 16 hours; bolts with light stress
Light intensity (PPFD)	200 to 300 µmol/m²/s House practice	No published source states this figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	5 to 10 days Updated to match the sources Was 3 to 7 days before September 2026	University of Minnesota Extension, Ask Extension answer on bok choy University or research 7 to 10 days Botanical Interests, Baby Choi Bok Choy seed packet Seed company or maker 5 to 10 days
Spacing	6 to 8 inches between plants Backed by sources	UF/IFAS HS1337, bok choy production University or research 8-inch plant spacing Botanical Interests, Baby Choi Bok Choy seed packet Seed company or maker thin to 1 every 6 inches
Plant height	8 to 12 inches for baby types, 12 to 18 for full heads Partly backed Was 8 to 12 inches for compact varieties before September 2026	Botanical Interests, Baby Choi Bok Choy seed packet Seed company or maker plant height 12 to 24 inches
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Lanitex Hydro Garden, Grow Bok Choy (Australia) Grower or shop guide 50 to 70%
First harvest	25 to 35 days baby, 6 to 8 weeks full heads Partly backed Was 25 to 35 days before September 2026	UF/IFAS HS1337 University or research 40 to 50 days after seeding (10 to 15 leaves) Botanical Interests, Baby Choi Bok Choy Seeds Seed company or maker baby choi in about 35 days

Butterhead Lettuce

Number	What the site says	Sources checked
pH	5.5 to 6.8 Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 5.6 to 6.0, set to 5.8 Holmes, Improving Lettuce Production in Deep Water Culture in the Southeastern United States (Auburn University thesis) University or research optimal pH 5.8 to 6.5, EC 1.5
EC, seedling	1.0 to 1.2 Filled from sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 1.2 for seedlings UF/IFAS AE610, How Efficient Are Hydroponic Lettuce Production Systems University or research 1.2 during germination
EC, mature	0.8 to 1.4 Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 1.2 UF/IFAS AE610, How Efficient Are Hydroponic Lettuce Production Systems University or research 1.2 as good as 1.6
Water temperature	65 to 75°F (18 to 24°C), with aeration above 72°F (site-wide rule) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Purdue University CEA, Growing hydroponic lettuce using heated nutrient solution under cooler air temperature University or research best growth at 71.5°F, the warmest of 60.5 to 71.4°F tested Cornell CEA Program, Hydroponic Lettuce Handbook (2013), research summary University or research optimum 24°C air and 24°C water
Air temperature	64 to 72°F Backed by sources	Purdue University (Miller & Nemali), butterhead 'Rex' trial University or research 70/65°F far better than 60/55°F Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 24°C day optimum
Light hours	14 hours on, 10 hours off Partly backed	Purdue University CEA, Growing hydroponic lettuce using heated nutrient solution under cooler air temperature University or research 16-hour photoperiod, DLI about 11.5 (one trial’s setting) Holmes, Improving Lettuce Production in Deep Water Culture in the Southeastern United States (Auburn University thesis) University or research high temperatures and long photoperiods cause bolting
Light intensity (PPFD)	about 240 to 340 µmol/m²/s at 14 hours (DLI 12 to 17) Partly backed Was 150 to 300 µmol/m²/s before September 2026	Cornell CEA Program, Hydroponic Lettuce Handbook (2013), set-points University or research 17 mol/m²/day Purdue Extension HO-283-W (Nemali and Langenhoven) University or research leafy greens 15 to 20 mol/m²/day
Light height	6 to 8 in House practice	No published source states this figure.
Germination	2 to 5 days; germination drops above 80°F Filled from sources	Utah State University Extension, Lettuce in the Garden University or research 7 to 10 days at 55 to 65°F; above 80°F reduces germination (soil growing)
Spacing	6 to 8 inches centre to centre Backed by sources	Purdue University CEA, heated nutrient solution lettuce trial University or research 8 x 6 inches Alabama Cooperative Extension System, Greenhouse Lettuce Production University or research 8-inch centres
Plant height	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Humidity	50 to 70% Partly backed Was 40 to 60% before September 2026	Cornell CEA Program, Hydroponic Lettuce Handbook (2013), set-points University or research minimum 50, maximum 70% Holmes, Auburn University thesis (DWC lettuce, southeastern US) University or research high humidity makes tipburn more likely
First harvest	30 to 45 days Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 35 days from seed Alabama Cooperative Extension, Greenhouse Lettuce Production University or research 30 days from transplant

Calendula

Number	What the site says	Sources checked
pH	5.5 to 6.2 Partly backed	Utah State University Extension, How to Grow Calendula in Your Garden University or research soil pH 6 to 7 (soil growing) LaNiTex Hydro Garden, Hydroponic calendula Grower or shop guide 5.5 to 6.2
EC, seedling	1.2 House practice	No published source states this figure.
EC, mature	1.2 to 1.8 Partly backed	LaNiTex Hydro Garden, Hydroponic calendula Grower or shop guide 1.2 to 1.8 MicroGarden Hacks, Growing Hydroponic Calendula Grower or shop guide 1.5 to 2.0
Water temperature	64 to 75°F (18 to 24°C) House practice	No published source states this figure.
Air temperature	64 to 75°F Partly backed	LaNiTex Hydro Garden, Hydroponic calendula Grower or shop guide 18 to 24°C MicroGarden Hacks, Growing Hydroponic Calendula Grower or shop guide 55 to 70°F; bloom drops above 80°F
Light hours	14 hours on, 10 hours off Partly backed	Growth and flowering characteristics of Calendula under different light spectra in a controlled environment (plant factory study) University or research 14 h photoperiod at 250 µmol
Light intensity (PPFD)	Not documented Partly backed	Nothing reliable was found, so the site gives no figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 14 days at about 70°F; cover the seed, light slows germination Partly backed Was 7 to 10 days before September 2026	University of Wisconsin-Madison Extension, Calendula University or research 5 to 15 days; light inhibits germination UNH Extension, How to grow calendula University or research 10 to 15 days
Spacing	8 to 12 inches Backed by sources	Utah State University Extension, Calendula in the Garden University or research 8 to 12 inches Johnny's Selected Seeds, Calendula Key Growing Information Seed company or maker 6 to 12 inches
Plant height	12 to 24 inches Backed by sources	Utah State University Extension, Calendula in the Garden University or research 8 to 24 inches University of Wisconsin-Madison Extension, Calendula University or research compact cultivars 12 inches; others 20 to 24
Humidity	50 to 70% Partly backed Was 40 to 50% before September 2026	Growth and flowering characteristics of Calendula under different light spectra in a controlled environment University or research 70 to 80% (one trial’s setting)
First harvest	6 to 8 weeks Backed by sources	UNH Extension, How to grow calendula University or research 30 to 50 days to maturity American Meadows, How to Grow Calendula Seed company or maker 6 to 8 weeks after sowing

Celery

Number	What the site says	Sources checked
pH	6.3 to 6.5 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research EC 1.8 to 2.4, pH 6.5 Oregon State University Horticulture, Celery production guide University or research 5.2 to 6.5 (soil growing)
EC, seedling	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
EC, mature	1.8 to 2.4 Partly backed Was 1.0 to 2.4 before September 2026	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 1.8 to 2.4 Ponics Life, Hydroponic Celery grow guide Grower or shop guide 1.8 to 2.4
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	60 to 65°F Filled from sources	Utah State University Extension, How to Grow Celery in Your Garden University or research 55 to 65°F ideal Oregon State University Horticulture, Celery production guide University or research avoid means below 55°F for 10 to 14 days
Light hours	14 hours on, 10 hours off Partly backed	Frosty Garden, Growing celery in cold climates (subarctic) Grower or shop guide 12 to 16 hours; they use 14
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	2 to 4 weeks; press the seed onto the surface, it needs light Partly backed Was 2 to 3 weeks before September 2026	Botanical Interests, Utah Celery seed packet Seed company or maker 15 to 30 days; press seed into the surface
Spacing	6 to 8 inches Backed by sources	Oregon State University, Oregon Vegetables: Celery University or research 6 to 8 inches within the row Utah State University Extension, Celery in the Garden University or research 12 inches; tight planting forces tall stalks
Plant height	12 to 24 inches Partly backed	Botanical Interests, Utah Celery seed packet Seed company or maker 12 to 24 inches
Humidity	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
First harvest	3 to 4 months Backed by sources	Utah State University Extension, How to Grow Celery in Your Garden University or research 10 to 12 weeks from planting out Oregon State University Horticulture, Celery production guide University or research June 1 transplant, harvest about October 1

Cherry Tomatoes

Number	What the site says	Sources checked
pH	5.8 to 6.5 Backed by sources	Ohio State University CFAES, Hydroponic Nutrient Solution for Optimized Greenhouse Tomato Production University or research 5.5 to 6.5 Alabama Cooperative Extension, Greenhouse Tomato Production University or research EC 2.0 to 2.5, pH 5.5 to 6.5
EC, seedling	1.0 to 1.2 Partly backed	Greenway Biotech, Step-by-Step Guide to Growing Hydroponic Tomatoes Seed company or maker 1.0 to 1.5 for seedlings Alabama Cooperative Extension, Greenhouse Tomato Production University or research clear water, then 50 ppm N after true leaves
EC, mature	2.0 to 2.5 Backed by sources	Alabama Cooperative Extension, Greenhouse Tomato Production University or research 2.0 to 2.5 Oregon State University Horticulture, Tomato, Greenhouse University or research held at 2.5 in closed systems
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Shamshiri et al. 2018, Review of optimum temperature, humidity, and vapour pressure deficit for greenhouse cultivation of tomato, International Agrophysics University or research root zone 27°C ideal (Jones 2013); 23°C least stress in summer (Li et al. 2015)
Air temperature	65 to 80°F Backed by sources	Oregon State University Horticulture, Tomato, Greenhouse University or research days 70 to 75°F; nights 62 to 65°F minimum Alabama Cooperative Extension, Greenhouse Tomato Production University or research 80 to 85°F days
Light hours	14 hours on, 10 hours off; fruiting crops may run to 16 Backed by sources	Schwarz, Thompson et al. 2014, Guidelines to use tomato in experiments with a controlled environment, Frontiers in Plant Science 5:625 University or research 8 to 16 hours Utah State University Extension, Tomatoes in the Garden University or research transplants lit 14 to 16 hours
Light intensity (PPFD)	DLI 20 or more, about 400 to 600 µmol/m²/s at 14 to 16 hours Updated to match the sources Was 600 to 900 µmol/m²/s; many home setups run 400 to 600 as a compromise before September 2026	Nemali and Langenhoven, Purdue Extension HO-283-W University or research tomatoes and strawberries more than 20 mol/m²/day Compact tomato cultivars under different DLI and photoperiod indoors, Agronomy 2022, 12(7), 1704 (MDPI) University or research DLI 10.4 to 18.4 with 12 to 16 h photoperiods
Light height	8 to 12 in Partly backed	LetPot, How to grow hydroponic cherry tomatoes indoors Grower or shop guide within about 30 cm
Germination	5 to 10 days Backed by sources	Cornell Garden-Based Learning, Tomato Growing Guide University or research 6 to 12 days; about a week at 75°F Schwarz, Thompson et al. 2014, Frontiers in Plant Science 5:625 University or research 4 days at 25 to 27°C
Spacing	12 to 18 inches between plants Backed by sources	Cornell Garden-Based Learning, Tomato Growing Guide University or research determinate 12 to 24 inches Alabama Cooperative Extension System, Greenhouse Tomato Production University or research 16 inches in-row
Plant height	2 to 4 feet indoors unless heavily pruned Backed by sources	Cornell Garden-Based Learning, Tomato Growing Guide University or research compact type about 3 feet
Humidity	50 to 70%; hand-pollinate midday when it is 60 to 70% Partly backed Was 40 to 70% with airflow before September 2026	Oregon State University, Oregon Vegetables: Tomato (greenhouse) University or research 60 to 80% in daylight Alabama Cooperative Extension System, Greenhouse Tomato Production University or research pollinate at 60 to 70%
First harvest	8 to 12 weeks from transplant Partly backed	Alabama Cooperative Extension, Greenhouse Tomato Production University or research transplants take 4 to 6 weeks Johnny's Selected Seeds, Cherry Tomato Seeds Seed company or maker 55 to 79 days

Chives

Number	What the site says	Sources checked
pH	6.0 to 6.5 Partly backed Was 5.5 to 6.5 before September 2026	University of Minnesota Extension, Growing chives in home gardens University or research 6.0 to 7.0 (soil growing) Salve Regina University Hydroponic Growing Guide (chives) University or research optimal 6.1 to 7.8, target 6.5
EC, seedling	1.0 to 1.2 House practice	No published source states this figure.
EC, mature	1.8 to 2.0 Backed by sources	Growth and quality of chives in hydroponic system with concentrations of magnesium sulfate (Horticultura Brasileira) University or research solution EC 2.00 to 2.11 during cultivation (one trial’s setting) Salve Regina University Hydroponic Growing Guide (chives) University or research 1260 to 1540 ppm, target 1350 (about 1.8 to 2.2 mS/cm if the meter used the 0.7 scale)
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 75°F Partly backed	Agrowtronics, Hydroponic Chives: The Grow Guide Grower or shop guide 65 to 80°F Hortivinyl, Hydroponic Chives Cultivation Grower or shop guide 15 to 25°C
Light hours	14 hours on, 10 hours off. Chives tolerate 12 to 14, but run 14/10 for Partly backed	Burpee Garden Encyclopedia, Chives Seed company or maker seedlings 16 hours on, 8 off under lights
Light intensity (PPFD)	200 to 300 µmol/m²/s House practice	No published source states this figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 14 days Backed by sources	Johnny's Selected Seeds, Chives Key Growing Information Seed company or maker 7 to 14 days at 65 to 70°F Burpee Garden Encyclopedia, Chives Seed company or maker 7 to 14 days
Spacing	3 to 4 inches between clumps Backed by sources	Utah State University Extension, Chives in the Garden University or research 4 to 6 inches Burpee Garden Encyclopedia, Chives Seed company or maker thin to 3 inches
Plant height	10 to 14 inches Backed by sources	Utah State University Extension, Chives in the Garden University or research 8 to 10 inches Johnny's Selected Seeds, Chives Key Growing Information Seed company or maker 12 to 18 inches
Humidity	50 to 70% House practice Was 40 to 70% before September 2026	No published source states this figure.
First harvest	7 to 9 weeks from seed Partly backed Was 5 to 7 weeks before September 2026	Salve Regina University Hydroponic Growing Guide (chives) University or research transferred on day 15, first harvest 52 days in the tower (about 9 to 10 weeks from seed) Agrowtronics, Hydroponic Chives: The Grow Guide Grower or shop guide about 4 weeks to transplant, then 3 to 4 weeks (7 to 8 weeks from seed)

Cilantro

Number	What the site says	Sources checked
pH	6.0 to 6.5 Sources disagree Was 6.5 to 6.7 before September 2026	Upstart University, Are You Growing Cilantro in Hydroponics? Grower or shop guide 6.5 to 6.7 LetPot, How to grow cilantro hydroponically indoors Grower or shop guide 5.5 to 6.5 Grow With Hydroponics, How to Grow Hydroponic Cilantro Grower or shop guide 5.5 to 6.5; wider figures up to 6.8 usually reflect soil guidance
EC, seedling	1.0 to 1.2 Partly backed	Grow With Hydroponics, How to Grow Hydroponic Cilantro Grower or shop guide 1.2 to 1.4 for seedlings Walters & Currey 2019, Agronomy 9(7):389 (cilantro, dill and parsley in NFT) University or research seedlings on 100 mg/L N for 3 weeks
EC, mature	1.4 to 1.8 Backed by sources	Walters & Currey 2019, Agronomy 9(7):389 University or research EC did not affect growth between 0.5 and 4.0; light did Upstart University, Are You Growing Cilantro in Hydroponics? Grower or shop guide 1.6 to 1.8
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Currey and Walters 2019, Nutrient Solution Strength Does Not Interact with the Daily Light Integral to Affect Hydroponic Cilantro, Dill, and Parsley Growth, Agronomy 9(7):389 (Iowa State) University or research solution held at 22.0°C (one trial’s setting) Grow With Hydroponics, Hydroponic Cilantro Guide Grower or shop guide 18 to 24°C; above 24°C (75°F) speeds bolting
Air temperature	60 to 70°F Backed by sources	UC Davis Western Institute for Food Safety and Security, Cilantro production summary University or research 50 to 85°F optimal; hot weather causes bolting LetPot, How to grow cilantro hydroponically indoors Grower or shop guide 15 to 20°C
Light hours	14 hours on, 10 hours off Partly backed	University of Missouri Extension G6986, Controlled Environment Agriculture: Hydroponic Farming (2024) University or research 12 to 16 hours of light a day Currey and Walters 2019, Agronomy 9(7):389 University or research 16-hour photoperiod
Light intensity (PPFD)	250 to 350 µmol/m²/s (DLI 12 to 18). More light grows much more cilantro Updated to match the sources Was 200 to 300 µmol/m²/s before September 2026	Currey and Walters 2019, Agronomy 9(7):389 University or research high DLI (about 18) raised cilantro fresh mass 154% over low (about 7) Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press cilantro fresh weight rises linearly to DLI 20
Light height	6 to 8 in Partly backed	LetPot, How to grow cilantro hydroponically indoors Grower or shop guide 6 to 12 inches Urban Harvest Lab, citing Penn State Extension Grower or shop guide 14 to 16 hours under two 40 W fluorescent tubes 6 to 12 inches from the canopy
Germination	7 to 10 days Backed by sources	Johnny's Selected Seeds, Cilantro (Coriander) Key Growing Information Seed company or maker 7 to 10 days at 65 to 70°F Utah State University Extension, Cilantro/Coriander in the Garden University or research about 21 days in the garden (soil growing)
Spacing	4 to 6 inches Partly backed	Currey and Walters 2019, Agronomy 9(7):389 University or research 20 cm (8 inch) centres, 25 plants per m² Utah State University Extension, Cilantro/Coriander in the Garden University or research 2 inches for leaves
Plant height	12 to 18 inches if left; harvest from 4 to 6 inches Partly backed Was 8 to 14 inches before September 2026	Johnny's Selected Seeds, Cilantro (Coriander) Key Growing Information Seed company or maker 12 to 18 inches
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	University of Missouri Extension G6986, Controlled Environment Agriculture: Hydroponic Farming (2024) University or research 50 to 60% in most hydroponic facilities
First harvest	6 to 8 weeks from seed Updated to match the sources Was 4 to 5 weeks before September 2026	Walters & Currey 2019, Agronomy 9(7):389 University or research 3 weeks as seedlings, harvested 4 weeks after transplant (7 weeks from seed) Upstart University, Are You Growing Cilantro in Hydroponics? Grower or shop guide 50 to 55 days from seed; first partial harvest about 5 weeks after transplant

Dill

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Utah State University Extension, How to Grow Dill in Your Garden University or research 5.5 to 6.5 (soil growing)
EC, seedling	1.0 to 1.2 House practice	No published source states this figure.
EC, mature	1.4 to 1.8 Backed by sources	Walters & Currey 2019, Agronomy 9(7):389 University or research no growth difference between EC 0.5 and 4.0 Kansas State University thesis, Optimization of nutrient solution management for leafy greens (review of Currey et al. 2019) University or research 0.5 to 4.0 made no difference to shoot weight
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Currey and Walters 2019, Agronomy 9(7):389 (Iowa State) University or research solution held at 22.0°C Walters (University of Tennessee) and Lopez (Michigan State) 2021, PLOS One 16(3):e0248662 University or research fresh mass rose as mean daily temperature went from about 10 to 27°C
Air temperature	65 to 75°F Partly backed	Walters & Lopez 2021, PLoS ONE 16(3):e0248662 (Michigan State University) University or research fresh mass rose near-linearly up to 27.2°C Utah State University Extension, How to Grow Dill in Your Garden University or research oil content rises with longer days and higher temperatures
Light hours	14 hours on, 10 hours off Partly backed	Walters and Lopez 2021, PLOS One 16(3):e0248662 University or research 16 h photoperiod (one trial’s setting) Utah State University Extension, Dill in the Garden University or research oil content rises with longer days
Light intensity (PPFD)	250 to 350 µmol/m²/s (DLI 12 to 18). Dill gains more from extra light than any other herb tested Updated to match the sources Was 200 to 300 µmol/m²/s before September 2026	Currey and Walters 2019, Agronomy 9(7):389 University or research high DLI (about 18) raised dill fresh mass 241% Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press dill a high-light herb; still rising at DLI 20
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 21 days Partly backed Was 7 to 14 days before September 2026	Utah State University Extension, Dill in the Garden University or research 7 to 21 days Johnny's Selected Seeds, Dill Key Growing Information Seed company or maker 7 to 21 days at 65 to 70°F
Spacing	4 to 6 inches between plants Partly backed	Utah State University Extension, Dill in the Garden University or research thin to 9 inches Johnny's Selected Seeds, Dill Key Growing Information Seed company or maker transplants 2 to 4 inches apart
Plant height	12 to 24 inches if not pruned House practice	No published source states this figure.
Humidity	50 to 70% House practice Was 40 to 70% before September 2026	No published source states this figure.
First harvest	6 to 8 weeks from seed Updated to match the sources Was 30 to 40 days before September 2026	Utah State University Extension, How to Grow Dill in Your Garden University or research 6 to 8 weeks after sowing Walters & Currey 2019, Agronomy 9(7):389 University or research 3 weeks as seedlings plus 4 weeks in NFT (7 weeks)

Dwarf Cucumber

Number	What the site says	Sources checked
pH	5.5 to 6.0 Partly backed Was 5.8 to 6.2 before September 2026	UF/IFAS HS790/CV268, Greenhouse Cucumber Production (Florida Greenhouse Vegetable Production Handbook) University or research 5.5 to 6.0 Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research EC 1.7 to 2.0, pH 5.0 to 5.5
EC, seedling	1.0 to 1.5 Partly backed Was about 1.7 before September 2026	Rise Gardens, Hydroponic cucumbers: the crisp vegetable you can grow indoors year round Grower or shop guide 1.0 to 1.5 for seedlings
EC, mature	1.8 to 2.4 Backed by sources	Oregon State University Horticulture, Cucumbers, Greenhouse University or research 2.2 in low light, 2.5 in bright light Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 1.7 to 2.0
Water temperature	65 to 75°F (18 to 24°C). Cool roots even in a warm room Backed by sources Was 65 to 72°F (18 to 22°C) before September 2026	Al-Rawahy et al. 2018, Effect of Cooling Root-Zone Temperature on Growth, Yield and Nutrient Uptake in Cucumber Grown in Hydroponic System During Summer Season in Cooled Greenhouse, Journal of Agricultural Science 11(1):47 University or research cooled root zone of 22°C gave the most fruit UF/IFAS HS790/CV268, Greenhouse Cucumber Production (Florida Greenhouse Vegetable Production Handbook, Vol 3) University or research avoid high solution temperatures
Air temperature	70 to 85°F Backed by sources	UF/IFAS HS790/CV268, Greenhouse Cucumber Production University or research 80 to 85°F; minimum 65°F University of Alaska Fairbanks Cooperative Extension, Growing Cucumbers in Greenhouses University or research 75 to 80°F by day
Light hours	16 hours on, 8 off. EXCEPTION: a true fruiting crop, not the herb 14/10 Partly backed	University of Alaska Fairbanks Cooperative Extension, Growing Cucumbers in Greenhouses University or research seedlings at least 14 hours
Light intensity (PPFD)	300 to 600 µmol/m²/s; aim for the top of the range (DLI 30) Backed by sources Was 300 to 600 µmol/m²/s before September 2026	Alabama Cooperative Extension System, Greenhouse Cucumber Production University or research optimum DLI 30 or more
Light height	8 to 12 in House practice	No published source states this figure.
Germination	3 to 10 days; as fast as 2 to 3 days at about 84°F Updated to match the sources Was 7 to 10 days at warm temperatures before September 2026	UF/IFAS HS790/CV268, Greenhouse Cucumber Production University or research 2 to 3 days at 84°F Seed Savers Exchange, Grow Cucumber Seed company or maker 4 to 10 days
Spacing	12 to 18 inches Backed by sources	Alabama Cooperative Extension System, Greenhouse Cucumber Production University or research 12 to 18 inches within the row
Plant height	3 to 5 feet trellised, in any direction House practice	No published source states this figure.
Humidity	50 to 70% Backed by sources	Alabama Cooperative Extension System, Greenhouse Cucumber Production University or research 60 to 70%; above that, more disease
First harvest	2 to 3 months Backed by sources	University of Alaska Fairbanks Cooperative Extension, Growing Cucumbers in Greenhouses University or research 50 to 70 days after seeding Bayer (Seminis), Greenhouse Production of Long English Cucumbers Seed company or maker 8 to 12 weeks after seeding

Dwarf Peppers

Number	What the site says	Sources checked
pH	5.8 to 6.3 Partly backed Was 5.8 to 6.5 before September 2026	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research EC 0.8 to 1.8, pH 5.5 to 6.0 Rise Gardens, Best Hydroponic Nutrients for Peppers Grower or shop guide 5.8 to 6.3
EC, seedling	1.0 to 1.2 Partly backed	Rise Gardens, Best Hydroponic Nutrients for Peppers Grower or shop guide 0.8 to 1.2 in weeks 1 to 2 Currey (Iowa State University), Peppers 101: a production guide, Produce Grower Trade press about 0.5 during propagation
EC, mature	2.0 to 2.5 Backed by sources	Hort Americas, Nutrient recipe for hydroponic greenhouse bell peppers Seed company or maker 2.2 for 0 to 6 weeks, 2.5 mature Currey (Iowa State University), Peppers 101: a production guide, Produce Grower Trade press 2.0 to 2.5 after transplant
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	LetPot, How to grow hydroponic bell peppers indoors Grower or shop guide 18 to 22°C
Air temperature	70 to 80°F Partly backed	NT Hydroponics, Hydroponic Bell Pepper Growing Guide Grower or shop guide 70 to 80°F day, 60 to 70°F night Rise Gardens, A Hydroponic System for Orange Peppers Grower or shop guide 70 to 80°F day, 65 to 70°F night
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	DLI 20 or more, about 400 to 600 µmol/m²/s at 14 to 16 hours Updated to match the sources Was 600 to 900 µmol/m²/s (many home setups run 400 to 700) before September 2026	NT Hydroponics, Hydroponic bell pepper growing guide Grower or shop guide DLI 20 to 30, 14 to 16 hours
Light height	8 to 12 in House practice	No published source states this figure.
Germination	7 to 18 days; faster when kept at 75 to 80°F Partly backed Was 7 to 14 days before September 2026	Seed Savers Exchange, Grow Pepper Seed company or maker 14 to 18 days
Spacing	About 12 inches between plants Backed by sources	Oklahoma State University Extension, Pepper Production University or research 12 to 16 inches Growth and Production of Hydroponic Pepper under Salt Stress and Plant Density, American Journal of Plant Sciences 2017 University or research 30 cm spacing gave more fruit per plant than 20 cm
Plant height	12 to 24 inches for dwarf/mini types House practice	No published source states this figure.
Humidity	50 to 70% with airflow Partly backed Was 40 to 70% with airflow before September 2026	No published source states this figure.
First harvest	10 to 14 weeks Partly backed	Haifa Group, Nutritional recommendations for pepper Seed company or maker first harvest 70 days after planting (greenhouse, Israel) IGWorks, Growing Hydroponic Peppers Grower or shop guide about 3 months from seed

Garlic Chives

Number	What the site says	Sources checked
pH	6.0 to 6.5 Partly backed	LetPot, How to Grow Hydroponic Garlic Chives Grower or shop guide 6.0 to 6.5
EC, seedling	1.0 to 1.3 Partly backed	LetPot, How to Grow Hydroponic Garlic Chives Grower or shop guide seedling 1.0 to 1.3
EC, mature	1.4 to 2.0 Partly backed	LetPot, How to Grow Hydroponic Garlic Chives Grower or shop guide growth 1.0 to 1.5; maturity 1.5 to 1.8
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 77°F Partly backed Was 65 to 80°F before September 2026	LetPot, How to Grow Hydroponic Garlic Chives Grower or shop guide 18 to 25°C
Light hours	14 hours on, 10 hours off Partly backed	Hydroponic Chinese chive salinity study (Frontiers in Nutrition 2022, 9:1000271, PMC9686344) University or research 10 h light / 14 h dark (one trial’s setting)
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 14 days Backed by sources	UNH Extension, How to grow garlic chives (Allium tuberosum) University or research 7 to 14 days Cornell Home Gardening, Garlic chives University or research 7 to 21 days to emergence
Spacing	8 to 12 inches between clumps Partly backed Was 6 to 8 inches between clumps before September 2026	UNH Extension, How to grow garlic chives (Allium tuberosum) University or research 12 inches
Plant height	12 to 18 inches of leaf, 18 to 24 with flower stalks Partly backed Was 12 to 18 inches before September 2026	UNH Extension, How to grow garlic chives (Allium tuberosum) University or research 18 to 24 inches tall
Humidity	40 to 60%. Higher raises fungal risk in dense mats Partly backed	Hydroponic Chinese chive salinity study (PMC9686344) University or research 60 to 70%
First harvest	8 to 10 weeks from seed Updated to match the sources Was 5 to 7 weeks before September 2026	True Leaf Market, Heirloom Garlic Chives Seeds Seed company or maker 85 to 90 days to maturity Annie's Heirloom Seeds, Garlic Chives Seed company or maker 60 days

Green Onions

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Kane et al. 2006, Journal of Plant Nutrition 29(2):375-390 (Texas Tech University) University or research pH 6.5 gave more total biomass than 5.8 University of Minnesota Extension, Growing onions in home gardens University or research 6.0 to 7.0 (soil growing)
EC, seedling	1.0 to 1.2 Partly backed	LetPot, How to Grow Hydroponic Scallions Grower or shop guide seedling 800 to 1200 µS/cm
EC, mature	1.4 to 1.8 Partly backed	Rise Gardens, Hydroponic Green Onion Recipes Grower or shop guide 1.4 to 1.8 Canada Grow Supplies, How To Grow Hydroponic Green Onions Grower or shop guide 1.2 to 2.0
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Rise Gardens, Hydroponic green onion recipe Grower or shop guide 65 to 72°F
Air temperature	65 to 75°F Partly backed	Canada Grow Supplies, How To Grow Hydroponic Green Onions Grower or shop guide 65 to 75°F by day LetPot, How to Grow Hydroponic Scallions Grower or shop guide 18 to 22°C; slows below 16°C, stressed above 25°C
Light hours	14 hours on, 10 hours off Partly backed	University of Maryland Extension, Growing Onions in the Home Garden University or research long-day bulbing onions bulb at 15 to 16 hours
Light intensity (PPFD)	200 to 350 µmol/m²/s Partly backed	No published source states this figure.
Light height	6 to 8 in Partly backed	LetPot, How to Grow Hydroponic Scallions Grower or shop guide 6 to 12 inches
Germination	7 to 14 days Partly backed	No published source states this figure.
Spacing	2 to 3 inches between onions or small clumps Backed by sources	University of Maryland Extension, Growing Onions in the Home Garden University or research 2 inches for green onions University of Minnesota Extension, Growing scallions in home gardens University or research thin to one plant every inch
Plant height	10 to 16 inches foliage above net cup Partly backed	No published source states this figure.
Humidity	50 to 70% Partly backed	No published source states this figure.
First harvest	2 to 3 weeks* Backed by sources	Kane et al. 2006, Journal of Plant Nutrition 29(2):375-390 University or research harvested 30 days after transplanting flag-stage seedlings Nature & Nurture Seeds, Evergreen Hardy Green Onion (Allium fistulosum) Seed company or maker 65 days to maturity

Kale

Number	What the site says	Sources checked
pH	5.5 to 6.5 Partly backed	Easter, Tenaglia & Park, Assessing pH Growth Response of Hydroponic Kale (Arizona State University poster) University or research treatments centred on pH 6.0 in DWC (one trial’s setting) LetPot, How to grow hydroponic kale Grower or shop guide 5.5 to 6.5
EC, seedling	1.0 to 1.2 House practice	No published source states this figure.
EC, mature	1.6 to 2.0 Partly backed	IGWorks, Growing Hydroponic Kale Grower or shop guide 1.6 to 2.5 Yang, Samarakoon, Altland & Ling 2024, Agronomy 14(11):2704 (Ohio State ATI / USDA-ARS) University or research kale yield highest at 2.1; health compounds fall with higher EC
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	60 to 75°F Partly backed	NT Hydroponics, Hydroponic Kale guide Grower or shop guide 65 to 75°F day, 50 to 65°F night LetPot, How to grow hydroponic kale Grower or shop guide 15 to 25°C
Light hours	14 hours on, 10 hours off Partly backed	Influence of Electrical Conductivity on Plant Growth, Nutritional Quality and Phytochemical Properties of Kale and Collard Grown Using Hydroponics, Agronomy 2024, 14(11), 2704 University or research supplemental HPS lamps 16 h a day
Light intensity (PPFD)	250 to 400 µmol/m²/s Partly backed	Agronomy 2024, 14(11), 2704 (kale and collard EC study) University or research DLI 28.7, humidity 49.7% (one trial’s setting)
Light height	6 to 8 in House practice	No published source states this figure.
Germination	4 to 7 days Partly backed	No published source states this figure.
Spacing	8 to 10 inches between plants Backed by sources	University of Minnesota Extension, Growing collards and kale University or research 8 inches; 4 for baby leaves West Virginia University Extension, Growing Kale in West Virginia University or research thin to 9 to 12 inches
Plant height	12 to 18 inches indoors if not heavily pruned Partly backed	No published source states this figure.
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Agronomy 2024, 14(11), 2704 (kale and collard EC study) University or research average 49.7%
First harvest	30 to 45 days baby, about 8 weeks full leaves Partly backed Was 30 to 45 days before September 2026	Yang et al. 2024, Agronomy 14(11):2704 University or research harvested 4 weeks after transplanting Upstart University, Growing Kale in Hydroponics Grower or shop guide six weeks from transplant

Lemon Balm

Number	What the site says	Sources checked
pH	5.5 to 6.5 Partly backed	LetPot, How to Grow Hydroponic Lemon Balm Grower or shop guide 5.5 to 6.5 Rise Gardens, How to Grow Lemon Balm Indoors Grower or shop guide 6.0 to 7.0, sweet spot 6.2 to 6.5
EC, seedling	0.8 to 1.1 Partly backed	LetPot, How to Grow Hydroponic Lemon Balm Grower or shop guide seedling 0.8 to 1.1
EC, mature	1.0 to 1.6 Partly backed Was 1.0 to 1.3 before September 2026	LetPot, How to Grow Hydroponic Lemon Balm Grower or shop guide growth 1.0 to 1.3; maturity 1.3 to 1.6 Rise Gardens, How to Grow Lemon Balm Indoors Grower or shop guide 1.0 to 1.6
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	64 to 75°F Partly backed	LetPot, How to Grow Hydroponic Lemon Balm Grower or shop guide 18 to 24°C Rise Gardens, How to Grow Lemon Balm Indoors Grower or shop guide 65 to 75°F
Light hours	14 hours on, 10 hours off Partly backed	Frąszczak, Gąsecka, Golcz et al. 2015, The chemical composition of lemon balm and basil plants grown under different light conditions, Acta Scientiarum Polonorum Hortorum Cultus 14:93-104 (Poznań University of Life Sciences) University or research 16 h photoperiod, 65 to 70% RH (one trial’s setting)
Light intensity (PPFD)	about 160 to 300 µmol/m²/s (trials); the herb band is a safe start Filled from sources	Frąszczak, Gąsecka, Golcz et al. 2015, Acta Scientiarum Polonorum Hortorum Cultus 14:93-104 University or research about 160 to 166 µmol (one trial’s setting)
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 14 days at 65 to 70°F; press the seed in, do not cover, it needs light Filled from sources	Johnny's Selected Seeds, Lemon Balm Key Growing Information Seed company or maker 7 to 14 days at 65 to 70°F; seed needs light Baker Creek Heirloom Seeds, How to grow lemon balm Seed company or maker 7 to 14 days at 70°F
Spacing	about 12 inches (18 to 24 in the garden) Filled from sources	Utah State University Extension, Lemon Balm in the Garden University or research 18 to 24 inches in the garden Johnny's Selected Seeds, Lemon Balm Key Growing Information Seed company or maker 12 inches
Plant height	12 to 24 inches, bushy Partly backed	Johnny's Selected Seeds, Lemon Balm Key Growing Information Seed company or maker 18 to 26 inches
Humidity	50 to 70% House practice	No published source states this figure.
First harvest	6 to 8 weeks from seed Filled from sources	Johnny's Selected Seeds, Lemon Balm Key Growing Information Seed company or maker sow 6 to 8 weeks before transplanting LetPot, How to Grow Hydroponic Lemon Balm Grower or shop guide about 6 to 8 weeks for a first small harvest

Lemongrass

Number	What the site says	Sources checked
pH	6.0 to 7.0 Partly backed	Eden Green, Hydroponic Lemongrass Grower or shop guide 6.0 to 7.0 Growneer, How to Grow Lemongrass Using a Hydroponic System Grower or shop guide 6.0 to 7.0
EC, seedling	0.8 to 1.0 House practice	No published source states this figure.
EC, mature	1.6 to 2.4 Partly backed	Utah State University, Morphological and Physiological Responses of Cymbopogon citratus and Pennisetum alopecuroides to salinity University or research no foliar damage even at 10.0; growth fell at high EC Eden Green, Hydroponic Lemongrass Grower or shop guide 1.6 to 2.4
Water temperature	65 to 75°F (18 to 24°C), the house range since 24 Sep 2026. Lemongrass likes the warm end House practice Was 65 to 75°F (18 to 24°C) before September 2026	No published source states this figure.
Air temperature	70 to 85°F Partly backed	RHS, How to grow Lemongrass Trade press at least 13°C to thrive Eden Green, Hydroponic Lemongrass Grower or shop guide 70 to 85°F
Light hours	14 hours on, 10 off Partly backed	No published source states this figure.
Light intensity (PPFD)	150 to 200 µmol/m²/s while rooting, 200 to 250 once mature (vendor guidance; lemongrass tolerates much brighter light) Partly backed	Utah State University, salinity tolerance of lemongrass and ornamental grasses (Plant Sciences faculty publication 2041) University or research DLI averaged 28.8
Light height	6 to 8 in House practice	No published source states this figure.
Germination	14 to 35 days to germinate, warm and humid. Slow and uncommon; rooting a grocery stalk is quicker Filled from sources Was Slow and uncommon before September 2026	Baker Creek Heirloom Seeds, How to grow lemongrass Seed company or maker 14 to 35 days, warm and humid
Spacing	12 inches for a stalk harvested young; a full clump needs 2 to 3 feet Partly backed Was 12 inches before September 2026	UC ANR Small Farms Network, Lemongrass University or research 2 to 3 feet
Plant height	2 to 4 feet indoors, up to 6 in ideal conditions Partly backed Was 24 to 48 inches before September 2026	Utah State University Extension, Lemongrass in the Garden University or research 3 to 6 feet tall, 3 feet wide
Humidity	Prefers humid, tolerates household levels Backed by sources	UC ANR Small Farms Network, Lemongrass University or research 80 to 100% RH, 64 to 85°F
First harvest	2 to 4 months Partly backed	Eden Green, Hydroponic Lemongrass Grower or shop guide 80 to 100 days from cuttings Bonnie Plants, Growing & Planting Lemongrass Seed company or maker harvest at 12 inches with half-inch bases

Lettuce

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research pH 5.6 to 6.0, adjusted to 5.8 Purdue University (Miller & Nemali), Growing hydroponic lettuce using heated nutrient solution University or research 5.5 to 6.5 (one trial’s setting)
EC, seedling	1.0 to 1.2 Partly backed Was 1.0 to 1.1 before September 2026	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research seedling water held at 1200 µS/cm (1.2) above source water UF/IFAS AE610, How Efficient Are Hydroponic Lettuce Production Systems University or research 1.2 during germination, 1.5 to 1.8 in production
EC, mature	1.0 to 1.4 Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research pond solution at 1.2 UF/IFAS AE610, How Efficient Are Hydroponic Lettuce Production Systems University or research 1.6 did not grow more lettuce than 1.2
Water temperature	65 to 75°F (18 to 24°C) Updated to match the sources Was 65 to 72°F (18 to 22°C) before September 2026	Cornell CEA Program, Hydroponic Lettuce Handbook (2013), research summary University or research optimum 24°C air and 24°C water Purdue University CEA, Growing hydroponic lettuce using heated nutrient solution under cooler air temperature University or research best growth at 71.5°F, the warmest tested
Air temperature	65 to 75°F by day Partly backed Was 60 to 70°F before September 2026	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 24°C day is the optimum; 24/19°C day/night Purdue University (Miller & Nemali), Growing hydroponic lettuce using heated nutrient solution University or research 19.6 g at 60/55°F vs 69.5 g at 70/65°F
Light hours	14 hours on, 10 hours off Partly backed	UF/IFAS HS1422, Growing Lettuce in Small Hydroponic Systems University or research Florida cultivars adapted to 10 to 11 hours
Light intensity (PPFD)	about 240 to 340 µmol/m²/s at 14 hours (DLI 12 to 17) Backed by sources Was 200 to 300 µmol/m²/s before September 2026	Akter, Cammarisano, Ahamed et al. 2026, interactive effect of EC and light intensity on hydroponic butterhead lettuce, Scientific Reports 16:14803 University or research 240 µmol (of 145, 185, 240) gave the highest growth and yield Cornell CEA Program, Hydroponic Lettuce Handbook (2013), set-points University or research 17 mol/m²/day
Light height	6 to 8 in House practice	No published source states this figure.
Germination	2 to 5 days; needs light, so leave the hole open; germination drops above 80°F Backed by sources Was 2 to 5 days before September 2026	B.A. Kratky, University of Hawaii CTAHR HG-42, A Simple Hydroponic Growing Kit for Short-Term Vegetables (2002) University or research 2 to 4 days Utah State University Extension, Lettuce in the Garden University or research 7 to 10 days at 55 to 65°F; above 80°F reduces germination (soil growing)
Spacing	6 to 8 inches Backed by sources	Virginia Cooperative Extension SPES-464, hydroponic lettuce production University or research raft plant spaces 8 inches apart University of Maryland Extension, Growing Lettuce in the Home Garden University or research thin leaf lettuce to 4 to 8 inches
Plant height	6 to 8 inches Backed by sources	University of Maryland Extension, Growing Lettuce in the Home Garden University or research use from 5 to 6 inches; cut at 6 to 10
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Cornell CEA Program, Hydroponic Lettuce Handbook (2013), set-points University or research minimum 50, maximum 70%
First harvest	4 to 5 weeks first leaves, 7 to 8 weeks full heads Partly backed Was 4 to 5 weeks before September 2026	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 35 days from seed to a 5 oz head Alabama Cooperative Extension, Greenhouse Lettuce Production University or research about 30 days from transplant to harvest

Micro Herbs

Number	What the site says	Sources checked
pH	5.5 to 7.0 Backed by sources	Research on microgreens farming in vertical hydroponic system (Romania, conference paper) University or research pH 5.8 to 6.2 Rise Gardens, Growing Microgreens Hydroponically at Home Grower or shop guide 5.5 to 6.5
EC, seedling	1.2 max Backed by sources	Rise Gardens, Growing Microgreens Hydroponically at Home Grower or shop guide 0.8 to 1.2 Research on microgreens farming in vertical hydroponic system University or research first irrigation EC 0.8
EC, mature	1.0 to 1.2 Backed by sources	Research on microgreens farming in vertical hydroponic system University or research 1.0 to 1.2; basil raised 0.2 weekly
Water temperature	65 to 75°F (18 to 24°C), with aeration above 72°F (site-wide rule) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	59 to 75°F Backed by sources	Penn State Extension, Growing Microgreens University or research air 60 to 70°F Rise Gardens, Growing Microgreens Indoors Grower or shop guide 60 to 75°F
Light hours	14 hours on, 10 hours off Partly backed	Utah State University Extension, Grow Your Own Microgreens University or research grow lights 18 hours a day
Light intensity (PPFD)	200 to 400 µmol/m²/s for basil, typically 300. Micro-herb category generally 150 to 300 Partly backed	Microgreens Production: Exploiting Environmental and Cultural Factors for Enhanced Agronomical Benefits, Plants 2024, 13(18):2631 (review) University or research most studies use 100 to 300 µmol Virginia Cooperative Extension SPES-756, microgreens production University or research DLI 9 to 16
Light height	6 to 12 in Partly backed	Rise Gardens, Growing Microgreens Indoors Grower or shop guide 6 to 12 inches
Germination	Basil about 2 days with a heat mat. Cilantro slower. Mint several days to a week Partly backed	No published source states this figure.
Spacing	Not applicable. Sown densely Backed by sources	University of Arizona Cooperative Extension, Microgreens University or research 3/16 to 1/4 inch
Plant height	2 to 4 inches, cut before 3 inches for basil Backed by sources	Penn State Extension, Growing Microgreens University or research harvested at 1.5 to 3 inches
Humidity	40 to 60% House practice Was 60 to 70% for basil before September 2026	No published source states this figure.
First harvest	16 to 28 days Backed by sources	Research on microgreens farming in vertical hydroponic system University or research basil sold after 27 to 31 days Penn State Extension, Growing Microgreens University or research 7 to 21 days for microgreens generally

Microgreens

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Research on microgreens farming in vertical hydroponic system (Romania) University or research pH 5.8 to 6.2 Rise Gardens, Growing Microgreens Hydroponically at Home Grower or shop guide 5.5 to 6.5
EC, seedling	0.5 to 1.0 Backed by sources	Research on microgreens farming in vertical hydroponic system University or research first irrigation EC 0.8 Rise Gardens, Growing Microgreens Hydroponically at Home Grower or shop guide no nutrients for 5 to 7 days
EC, mature	0.8 to 1.2 Partly backed Was 0.5 to 1.0 before September 2026	Research on microgreens farming in vertical hydroponic system University or research 1.0 to 1.2 Growing Better Greenhouse Microgreens, GPN (Cornell University trials, Mattson lab) Trade press fresh weight rose from 0 to 200 ppm N
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 75°F Partly backed	Virginia Cooperative Extension SPES-756, Introduction to Microgreen Production in Indoor Vertical Farms University or research 60 to 70°F Growing Better Greenhouse Microgreens, GPN (Cornell University trials, Mattson lab) Trade press warmer (57 to 72°F) meant fewer days to harvest
Light hours	14 hours on, 10 hours off Partly backed	Botanical Interests, Grow microgreens year-round Seed company or maker 12 to 16 hours Utah State University Extension, Grow Your Own Microgreens University or research 18 hours
Light intensity (PPFD)	about 180 to 320 µmol/m²/s at 14 hours (DLI 9 to 16) Partly backed Was 125 to 250 µmol/m²/s depending on species and desired compactness before September 2026	Virginia Cooperative Extension SPES-756, microgreens production University or research DLI 9 to 16 Microgreens Production: Exploiting Environmental and Cultural Factors for Enhanced Agronomical Benefits, Plants 2024, 13(18):2631 (review) University or research most studies use 100 to 300 µmol
Light height	10 to 12 in Partly backed	Rise Gardens, Growing Microgreens Indoors Grower or shop guide 6 to 12 inches
Germination	1 to 4 days depending on species Partly backed	No published source states this figure.
Spacing	Sown densely across tray (hundreds of seedlings) Backed by sources	Johnny's Selected Seeds, Microgreens Key Growing Information Seed company or maker seeds 1/8 to 1/4 inch apart
Plant height	1.5 to 3 inches at harvest Backed by sources Was 2 to 4 inches at harvest before September 2026	Penn State Extension, Growing Microgreens University or research 1.5 to 3 inches
Humidity	40 to 60%; high RH encourages mold House practice	No published source states this figure.
First harvest	7 to 14 days Backed by sources	Penn State Extension, Growing Microgreens University or research 7 to 21 days Johnny's Selected Seeds, Microgreen Seeds Seed company or maker fast 10 to 15 days; slow 16 to 25

Mint

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Satpute et al., Design and evaluation of an automatic control system for hydroponics cultivation of mint (ICAR, New Delhi) University or research held at 6.0 to 6.5 (one trial’s setting) Comparative Performance of Mint in Different Hydroponics Systems, Madras Agricultural Journal 2022 (Tamil Nadu Agricultural University) University or research 6.5 to 6.8 (one trial’s setting)
EC, seedling	1.0 to 1.2 Partly backed	Rise Gardens, Hydroponic Mint Growing Guide Grower or shop guide half strength for the first 7 to 10 days
EC, mature	2.0 to 2.4 Backed by sources	Satpute et al., automatic control system for hydroponic mint (ICAR, New Delhi) University or research 2.0 to 2.5 Comparative Performance of Mint in Different Hydroponics Systems, Madras Agricultural Journal 2022 University or research around 2
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 75°F Partly backed	Upstart University, How to Grow Mint in Hydroponics Grower or shop guide 65 to 70°F; struggles above 80°F NoSoilSolutions, Growing Hydroponic Mint Made Easy (Scribd) Grower or shop guide 55 to 70°F
Light hours	14 hours on, 10 hours off Partly backed	Burpee Garden Encyclopedia, Mint Seed company or maker seedlings 16 hours on, 8 off
Light intensity (PPFD)	250 to 320 µmol/m²/s (DLI 12 to 16); more light does not add growth Partly backed Was 250 to 400 µmol/m²/s before September 2026	Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press mint peaks at DLI 15 to 16, then declines
Light height	6 to 8 in House practice	No published source states this figure.
Germination	10 to 15 days Backed by sources	Johnny's Selected Seeds, Mint Key Growing Information Seed company or maker 10 to 14 days at 72 to 75°F
Spacing	about 12 inches, or give mint its own container Updated to match the sources Was 6 to 8 inches between plants in shared totes; roots are aggressive before September 2026	Johnny's Selected Seeds, Mint Key Growing Information Seed company or maker 12 to 18 inches Burpee Garden Encyclopedia, Mint Seed company or maker 18 inches
Plant height	8 to 18 inches kept cut; 18 to 36 if left Partly backed Was 8 to 18 inches, sprawling sideways with pruning before September 2026	Johnny's Selected Seeds, Mint Key Growing Information Seed company or maker 18 to 36 inches
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Frontiers in Sustainable Food Systems 2021, water and nitrogen management of potted Mentha arvensis in an evaporative greenhouse University or research 60 to 65% RH
First harvest	4 to 5 weeks from a rooted cutting Partly backed	Johnny's Selected Seeds, Mint Key Growing Information Seed company or maker start seed 6 to 8 weeks before transplanting Rise Gardens, Hydroponic Mint Growing Guide Grower or shop guide 3 to 4 weeks from rooted cuttings

Mizuna

Number	What the site says	Sources checked
pH	5.8 to 6.5 Partly backed	West Coast Seeds, Mizuna Seed company or maker 6.0 to 6.5 LaNiTex Hydro Garden, How to Grow Mizuna Hydroponically Grower or shop guide 5.5 to 6.5
EC, seedling	0.8 to 1.0 Filled from sources	MicroGarden Hacks, Growing Hydroponic Mizuna Grower or shop guide start at 0.8
EC, mature	1.0 to 1.5 Partly backed	MicroGarden Hacks, Growing Hydroponic Mizuna Grower or shop guide 1.0 to 1.5 LaNiTex Hydro Garden, How to Grow Mizuna Hydroponically Grower or shop guide 1.2 to 2.0
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	59 to 77°F Partly backed	Purdue University thesis, Optimizing Controlled-Release Fertilizer for Lettuce and Mizuna Grown on the ISS University or research 24/21°C day/night LaNiTex Hydro Garden, How to Grow Mizuna Hydroponically Grower or shop guide 50 to 75°F, ideal 60 to 70°F
Light hours	14 hours on, 10 hours off Partly backed	Palmer and van Iersel 2020, Increasing Growth of Lettuce and Mizuna under Sole-Source LED Lighting Using Longer Photoperiods with the Same Daily Light Integral, Agronomy 10(11):1659 (University of Georgia) University or research at equal DLI, 20 h grew 18.7% more mizuna than 10 h
Light intensity (PPFD)	about 250 to 320 µmol/m²/s (DLI 13 to 16) Partly backed	Palmer and van Iersel 2020, Agronomy 10(11):1659 University or research DLI 16
Light height	6 to 8 in House practice	No published source states this figure.
Germination	3 to 6 days at 68 to 77°F Backed by sources	Baker Creek Heirloom Seeds, How to grow mizuna Seed company or maker 4 to 7 days; ideal 75°F
Spacing	7 inches (18 cm) in hydroponics Partly backed	West Coast Seeds, Mizuna Seed company or maker 4 to 6 inches in the row
Plant height	About 12 inches at harvest, up to 30 cm in plant-factory conditions Partly backed	No published source states this figure.
Humidity	50 to 70% House practice	No published source states this figure.
First harvest	21 days baby leaf Backed by sources	Johnny's Selected Seeds, Mizuna Organic Asian Green Seed company or maker 18 days baby; 40 full size MicroGarden Hacks, Growing Hydroponic Mizuna Grower or shop guide as little as 21 days

Mustard Greens

Number	What the site says	Sources checked
pH	5.5 to 6.8 Partly backed	IGWorks, Growing Hydroponic Mustard Greens Grower or shop guide 5.5 to 6.8 Upstart University, Growing Mustard Greens Grower or shop guide 6.0 to 7.5
EC, seedling	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
EC, mature	1.2 to 2.4 Partly backed	Upstart University, Growing Mustard Greens Grower or shop guide 1.2 to 2.4 IGWorks, Growing Hydroponic Mustard Greens Grower or shop guide 1.2 to 2.4
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	50 to 75°F Partly backed	Eden Green, Hydroponic Mustard Greens Grower or shop guide 50 to 75°F; optimal 60 to 70°F
Light hours	14 hours on, 10 hours off. Sources give 14 to 16 Partly backed	No published source states this figure.
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	6 to 8 in House practice	No published source states this figure.
Germination	4 to 7 days Filled from sources	Seed Savers Exchange, Grow Mustard Seed company or maker 4 to 7 days
Spacing	about 6 inches (4 to 6 in the row; large varieties up to 12) Filled from sources	Oregon State University, Oregon Vegetables: Mustard Greens University or research 4 to 6 inches in the row Seed Savers Exchange, Grow Mustard Seed company or maker thin to 6 to 18 inches by variety
Plant height	6 to 8 inches at harvest Filled from sources	Territorial Seed Company, Mustard growing guide Seed company or maker mature at 6 to 8 inches
Humidity	50 to 70% House practice	No published source states this figure.
First harvest	4 to 5 weeks Backed by sources	Territorial Seed Company, Mustard Greens growing guide Seed company or maker outer leaves at 30 to 40 days Bonnie Plants, Growing Mustard Greens Seed company or maker pick at about 4 weeks; full size at 6

Nasturtium

Number	What the site says	Sources checked
pH	6.0 to 7.0 Partly backed Was 6.1 to 7.8 before September 2026	Growth and production of nasturtium flowers in three hydroponic solutions (Brazil) University or research nursery solution kept at 5.8 to 6.2 (one trial’s setting) Upstart University, Growing Nasturtiums in hydroponics Grower or shop guide 6.1 to 7.8
EC, seedling	0.8 to 1.0 Partly backed	Growth and production of nasturtium flowers in three hydroponic solutions (Brazil) University or research nursery on 25% strength solution LaNiTex Hydro Garden, Growing Nasturtiums hydroponically Grower or shop guide 0.8 to 1.2 for seedlings
EC, mature	1.0 to 1.6 Partly backed	IGWorks, Growing Hydroponic Nasturtium Grower or shop guide 0.8 to 1.6 LaNiTex Hydro Garden, Growing Nasturtiums hydroponically Grower or shop guide 1.5 to 2.0
Water temperature	55 to 75°F (13 to 24°C) Partly backed	Melo et al. 2011, Growth and production of nasturtium flowers in three hydroponic solutions, Horticultura Brasileira 29(4):584-589 University or research solution around 25°C
Air temperature	55 to 75°F Partly backed	Upstart University, Growing Nasturtiums in hydroponics Grower or shop guide 55 to 75°F; adults best about 70°F Growth and production of nasturtium flowers in three hydroponic solutions (Brazil) University or research poor flowering at about 30°C
Light hours	16 hours on, 8 off Partly backed Was 14 hours on, 10 hours off before September 2026	Xu, Lu, Kikuchi and Takagaki 2021, Continuous Lighting and High Daily Light Integral Enhance Yield and Quality of Mass-Produced Nasturtium in Plant Factories, Plants 10(6):1203 (Chiba University) University or research at equal DLI, 24 h beat 16 h
Light intensity (PPFD)	at least 300 µmol/m²/s at 16 hours (DLI 17 or more); more light, more leaf Updated to match the sources Was 200 to 300 µmol/m²/s before September 2026	Xu, Lu, Kikuchi and Takagaki 2021, Plants 10(6):1203 University or research yield rises from DLI 17.3 to 34.6
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 10 days; bury the seed half an inch, it needs darkness Backed by sources	University of Wisconsin-Madison Extension, Nasturtium University or research 7 to 10 days; needs darkness; 10 to 12 inches apart Johnny's Selected Seeds, Nasturtium Key Growing Information Seed company or maker 7 to 14 days at 60 to 65°F
Spacing	8 to 12 inches Partly backed Was 6 to 8 inches before September 2026	Johnny's Selected Seeds, Nasturtium Key Growing Information Seed company or maker 8 to 12 inches
Plant height	compact types 6 to 12 inches (Tom Thumb, Tip Top); trailing types spread 12 inches or more Partly backed Was Bush to trailing before September 2026	University of Wisconsin-Madison Extension, Nasturtium University or research 'Tom Thumb' 6 to 9 inches
Humidity	50 to 70% Partly backed Was 40 to 50% before September 2026	Xu, Lu, Kikuchi and Takagaki 2021, Plants 10(6):1203 University or research 50 to 80%
First harvest	4 weeks leaves, 6 to 8 weeks flowers Partly backed Was 4 to 6 weeks before September 2026	IGWorks, Growing Hydroponic Nasturtium Grower or shop guide buds or flowers in 4 to 6 weeks Upstart University, Growing Nasturtiums in hydroponics Grower or shop guide flowers 5 to 6 weeks after transplant

Oregano

Number	What the site says	Sources checked
pH	5.5 to 6.5 Partly backed	UF/IFAS Extension Pasco County, A Beginner's Guide to Growing Oregano University or research 6.0 to 8.0 (soil growing) Grow With Hydroponics, Hydroponic Oregano guide Grower or shop guide 5.8 to 6.3; the 6.0 to 8.0 figure is for soil
EC, seedling	1.0 to 1.2 Partly backed	Grow With Hydroponics, Hydroponic Oregano guide Grower or shop guide 1.2 to 1.6 for a young plant
EC, mature	1.4 to 1.8 Partly backed Was 1.2 to 1.6 before September 2026	Rise Gardens, Growing Oregano Hydroponically Indoors Grower or shop guide 1.4 to 1.8 Upstart University, Growing Oregano in Hydroponics Grower or shop guide 1.5 to 2.0
Water temperature	65 to 75°F (18 to 24°C) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 75°F Partly backed	NoSoilSolutions, How To Grow Hydroponic Oregano Grower or shop guide 65 to 75°F Grow With Hydroponics, Hydroponic Oregano guide Grower or shop guide 18 to 24°C
Light hours	14 hours on, 10 hours off Partly backed	Burpee Garden Encyclopedia, Oregano Seed company or maker seedlings 16 hours on, 8 off
Light intensity (PPFD)	200 to 400 µmol/m²/s; aim for the top of the range (300 to 400) Partly backed Was 200 to 400 µmol/m²/s before September 2026	Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press oregano still gaining at DLI 20; high-light crop
Light height	4 to 6 in Partly backed	Eden Green, Hydroponic Oregano guide Grower or shop guide about 6 inches
Germination	7 to 14 days. Surface sow, needs light Backed by sources	Johnny's Selected Seeds, Oregano (Greek) Key Growing Information Seed company or maker 7 to 14 days at 65 to 70°F
Spacing	8 to 12 inches Updated to match the sources Was 6 inches before September 2026	Penn State Extension, Herb Garden Plants: Oregano University or research thin to 8 to 12 inches UF/IFAS Extension Pasco County, A beginner's guide to growing oregano University or research 10 to 12 inches, for air circulation
Plant height	8 to 24 inches, bushy; keep it to 6 to 8 by regular cutting Updated to match the sources Was 4 to 6 inches, trailing rather than climbing before September 2026	UF/IFAS Extension Pasco County, A beginner's guide to growing oregano University or research up to 2 feet tall, 18 inches wide Johnny's Selected Seeds, Oregano (Greek) Key Growing Information Seed company or maker 8 to 24 inches
Humidity	50 to 70% House practice Was 40 to 70% before September 2026	No published source states this figure.
First harvest	8 to 10 weeks Partly backed	Park Seed, Oregano Seeds Seed company or maker 60 days from transplant; first cuts under 2 months from sowing Upstart University, Growing Oregano in Hydroponics Grower or shop guide first harvest 8 weeks after transplant

Parsley

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 6.0 to 6.5 Camargos de Oliveira et al. 2024, Comunicata Scientiae 15:e4232 (parsley and lettuce in NFT) University or research 5.5 to 6.5 (one trial’s setting)
EC, seedling	1.0 to 1.2 Partly backed	Camargos de Oliveira et al. 2024, Comunicata Scientiae 15:e4232 University or research nursery on 50% strength solution until day 25 Walters & Currey 2019, Agronomy 9(7):389 (cilantro, dill, parsley) University or research seedlings on 100 mg/L N
EC, mature	1.4 to 1.8 Backed by sources	Walters & Currey 2019, Agronomy 9(7):389 University or research no growth difference between EC 0.5 and 4.0 Upstart University, Growing Hydroponic Parsley Grower or shop guide 0.8 to 1.8
Water temperature	65 to 75°F (18 to 24°C) Backed by sources Was 65 to 72°F (18 to 22°C) before September 2026	Walters (University of Tennessee) and Lopez (Michigan State) 2021, PLOS One 16(3):e0248662 University or research parsley fresh mass rose up to about 22.4°C Currey and Walters 2019, Agronomy 9(7):389 (Iowa State) University or research solution held at 22.0°C
Air temperature	65 to 75°F Backed by sources	Walters & Lopez 2021, PLoS ONE 16(3):e0248662 (Michigan State University) University or research fresh mass rose with temperature up to 22.4°C Upstart University, Growing Hydroponic Parsley Grower or shop guide 60 to 75°F
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	200 to 300 µmol/m²/s; aim for the top of the range (about 300, DLI 15) Backed by sources Was 200 to 300 µmol/m²/s before September 2026	Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press parsley peaks at DLI 15 to 16
Light height	6 to 8 in Partly backed	Alto Garden, How to Grow Hydroponic Parsley Grower or shop guide 6 to 12 inches
Germination	14 to 30 days; often 3 weeks or more, a 24-hour soak helps Updated to match the sources Was 14 to 21 days (slow) before September 2026	UC Davis Western Institute for Food Safety and Security, Parsley commodity profile University or research 21 to 25 days Johnny's Selected Seeds, Parsley Key Growing Information Seed company or maker 14 to 30 days at 65 to 70°F; at least 3 weeks
Spacing	4 to 6 inches between crowns Backed by sources	Purdue Extension HO-202, Parsley University or research transplants 4 to 8 inches apart
Plant height	10 to 18 inches depending on pruning Backed by sources	University of Minnesota Extension, Growing parsley University or research curly parsley 8 to 14 inches
Humidity	50 to 70% House practice Was 40 to 70% before September 2026	No published source states this figure.
First harvest	6 to 8 weeks Backed by sources	Walters & Currey 2019, Agronomy 9(7):389 University or research 3 weeks seedling plus 4 weeks in NFT (7 weeks) Camargos de Oliveira et al. 2024, Comunicata Scientiae 15:e4232 University or research transplanted at 25 days, commercial size 30 days later

Pea Pods

Number	What the site says	Sources checked
pH	6.2 to 6.5 Partly backed	MicroGarden Hacks, Growing Hydroponic Peas Grower or shop guide 6.0 to 6.8 Hydroponics.eu, Growing peas in the garden, in pots and in hydroponics Grower or shop guide 6 to 6.5
EC, seedling	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
EC, mature	1.2 to 1.8 Partly backed Was 0.8 to 1.9 before September 2026	MicroGarden Hacks, Growing Hydroponic Peas Grower or shop guide 1.2 to 1.8
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	60 to 70°F Filled from sources	MicroGarden Hacks, Growing Hydroponic Peas Grower or shop guide 60 to 70°F day; 50 to 60°F night Hydroponics.eu, Growing peas in the garden, in pots and in hydroponics Grower or shop guide 16 to 20°C optimal
Light hours	16 hours on, 8 off. Both hydroponic sources agree on 16 Partly backed	University of Maryland Extension, Growing Green Peas in the Home Garden University or research flowering accelerated by long, cool days
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Germination	7 to 14 days; soak overnight (no more than 24 hours) to speed it Backed by sources	Penn State Extension, A Gardener's Guide to Peas University or research 6 to 17 days; an overnight soak shortens it Seed Savers Exchange, Grow Peas Seed company or maker 7 to 14 days
Spacing	2 to 3 inches apart along a trellis Filled from sources	Penn State Extension, A Gardener's Guide to Peas University or research 1.5 to 3 inches in the row Seed Savers Exchange, Grow Peas Seed company or maker 2 to 3 inches apart
Plant height	over 5 feet for standard varieties, 2 to 3 feet for compact cultivars; Tom Thumb stays at 8 to 12 inches, the apartment pea Backed by sources Was Over 5 feet for standard varieties before September 2026	Cornell Vegetable Variety Trials (vegvariety.cce.cornell.edu), peas University or research 'Tom Thumb' 8 to 12 inches
Humidity	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
First harvest	8 to 10 weeks from seed Updated to match the sources Was 4 to 8 weeks before September 2026	Cornell Cooperative Extension, Vegetable Varieties for Gardeners (pea search) University or research snow and snap peas 50 to 80 days Territorial Seed Company, Peas growing guide Seed company or maker days to maturity from direct seeding

Romaine Lettuce

Number	What the site says	Sources checked
pH	5.5 to 6.8 Backed by sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research set to 5.8 ICAR-CISH Lucknow, Optimising electrical conductivity, pH and cultivar selection for hydroponic lettuce in subtropical environments University or research pH 6.5 to 7.5 superior; best at EC 2.2, pH 7.5
EC, seedling	1.0 to 1.2 Filled from sources	Cornell University CEA Program, Hydroponic Lettuce Handbook (2013) University or research 1.2 for seedlings
EC, mature	1.2 to 1.8 Partly backed Was 0.8 to 1.4 before September 2026	Kratky 2009, Three non-circulating hydroponic methods for growing lettuce, Acta Hort. 843 (University of Hawaii) University or research EC about 1.5 ICAR-CISH Lucknow, hydroponic lettuce EC and pH trial University or research yield highest at 2.2 (range tested 1.8 to 2.2)
Water temperature	65 to 75°F (18 to 24°C), with aeration above 72°F (site-wide rule) Backed by sources Was 65 to 72°F (18 to 22°C) before September 2026	Bantis, Tostsidis, Zervoudakis and Koukounaras 2026, Root-Zone Heating Boosts the Production of Mini Romaine Lettuce Grown in NFT and Aeroponics Systems, Plants 15(3):422 University or research 18 and 22°C gave 127 to 232% more leaf mass than 11 to 12°C Bantis et al. 2026, Plants 15(3):422 University or research heat the solution to at least 22°C in cool months
Air temperature	64 to 72°F Backed by sources	Purdue University (Miller & Nemali), heated nutrient solution trial University or research 70/65°F far better than 60/55°F Herbals NZ, Growing Romaine Lettuce Hydroponically Grower or shop guide 60 to 70°F
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	about 240 to 340 µmol/m²/s at 14 hours (DLI 12 to 17) Partly backed Was 150 to 300 µmol/m²/s (leafy green category) before September 2026	Comparison of Different Temperature Control Systems in Tropical-Adapted Greenhouses for Green Romaine Lettuce Production (2023), citing Ahmed et al.'s review University or research optimal lettuce light under artificial lighting 200 to 250 µmol; RH 70 to 80% Cornell CEA Program, Hydroponic Lettuce Handbook (2013), set-points University or research 17 mol/m²/day
Light height	6 to 8 in House practice	No published source states this figure.
Germination	2 to 5 days; germination drops above 80°F Backed by sources	Utah State University Extension, Lettuce in the Garden University or research 7 to 10 days at 55 to 65°F; above 80°F reduces germination
Spacing	8 to 10 inches centre to centre for full heads Backed by sources	Utah State University Extension, Lettuce in the Garden University or research head lettuce 8 to 12 inches University of Illinois Extension, How to grow lettuce (2020) University or research head lettuce 10 to 12 inches
Plant height	8 to 12 inches Filled from sources Was Tall upright head before September 2026	UF/IFAS HS1258, lettuce types (Florida) University or research romaine 8 to 12 inches tall
Humidity	50 to 70% Partly backed Was 40 to 60% before September 2026	No published source states this figure.
First harvest	40 to 50 days Backed by sources	Kratky 2009, Three non-circulating hydroponic methods for growing lettuce (University of Hawaii) University or research 6 to 7 weeks from seeding Herbals NZ, Growing Romaine Lettuce Hydroponically Grower or shop guide 60 to 75 days

Rosemary

Number	What the site says	Sources checked
pH	5.5 to 6.5 Partly backed	LetPot, How to grow rosemary hydroponically Grower or shop guide 5.5 to 6.5 Upstart University, How to Grow Classic Rosemary in Hydroponics Grower or shop guide 5.5 to 6.0
EC, seedling	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
EC, mature	1.2 to 1.6 Partly backed	Upstart University, How to Grow Classic Rosemary in Hydroponics Grower or shop guide 1.0 to 1.6 IGWorks, Growing Hydroponic Rosemary Grower or shop guide 1.0 to 1.6
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	65 to 80°F Partly backed	UMass Amherst Extension, Rosemary: Container Production for December Market University or research nights at 65°F Upstart University, How to Grow Classic Rosemary in Hydroponics Grower or shop guide 75 to 85°F
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	6 to 12 in Partly backed Was 4 to 6 in before September 2026	Alto Garden, How to Grow Rosemary Indoors Grower or shop guide 6 to 12 inches
Germination	14 to 28 days, slow and unreliable. Not recommended Backed by sources	UMass Extension, Rosemary Container Production for December Market University or research 12 to 28 days or more; seed not recommended Johnny's Selected Seeds, Rosemary Key Growing Information Seed company or maker 14 to 21 days at 65 to 70°F
Spacing	10 to 12 inches for a pruned indoor plant; 24 to 36 in the garden Partly backed Was 24 to 36 inches between plants before September 2026	UMass Extension, Rosemary Container Production for December Market University or research final spacing 10-inch centres for 6-inch pots Johnny's Selected Seeds, Rosemary Key Growing Information Seed company or maker 8 to 10 inches as an annual; 24 to 36 as a perennial
Plant height	2 to 3 feet indoors, up to 5 to 6 feet unpruned Backed by sources	Johnny's Selected Seeds, Rosemary Key Growing Information Seed company or maker 18 to 60 inches
Humidity	45 to 60%. Higher invites mildew House practice	No published source states this figure.
First harvest	8 to 12 weeks from a cutting Backed by sources	UMass Amherst Extension, Rosemary: Container Production for December Market University or research cuttings ready to transplant 17 to 21 days after sticking Johnny's Selected Seeds, Rosemary Key Growing Information Seed company or maker 80 to 100 days from planting for stem tips

Sage

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research EC 1.0 to 1.6, pH 5.5 to 6.5
EC, seedling	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
EC, mature	1.0 to 1.6 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 1.0 to 1.6 Kansas State University thesis, Optimization of nutrient solution management for leafy greens University or research 1.0 to 1.6
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	65 to 80°F House practice	No published source states this figure.
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	about 300 µmol/m²/s (DLI 15 to 16); more light does not add growth Partly backed	Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press sage peaks at DLI 15 to 16, then declines
Light height	4 to 6 in House practice	No published source states this figure.
Germination	10 to 21 days. Slow Backed by sources	Johnny's Selected Seeds, Common Sage Key Growing Information Seed company or maker 7 to 21 days at 65 to 70°F
Spacing	8 to 12 inches Backed by sources	Johnny's Selected Seeds, Common Sage Key Growing Information Seed company or maker 12 inches
Plant height	12 to 24 inches in containers Partly backed	Johnny's Selected Seeds, Common Sage Key Growing Information Seed company or maker 16 to 30 inches
Humidity	45 to 65% House practice	No published source states this figure.
First harvest	3+ months Backed by sources	Organo Republic, How to Grow Sage from Seed Seed company or maker 75 to 90 days to first harvest Seedstore, Extrakta Sage Seeds Seed company or maker 90 days

Shiso / Perilla

Number	What the site says	Sources checked
pH	5.8 to 6.2 Partly backed	Lu et al. 2017, Frontiers in Plant Science 8:708 (PMC5416839), perilla under PPFD x EC University or research seedling solution at EC 1.2, pH 6.0 (one trial’s setting) Harvest to Table, How to Plant, Grow, and Harvest Shiso Grower or shop guide 5.5 to 6.5
EC, seedling	0.8 to 1.0 Partly backed	Lu et al. 2017, Frontiers in Plant Science 8:708 University or research seedlings at EC 1.2
EC, mature	1.0 to 2.0 Partly backed Was 1.0 to 1.5 before September 2026	Lu et al. 2017, Frontiers in Plant Science 8:708 University or research more growth at EC 3.0 under strong light; rosmarinic acid up at low EC
Water temperature	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Air temperature	65 to 77°F Partly backed Was 60 to 75°F before September 2026	Lu et al. 2017, Frontiers in Plant Science 8:708 University or research 23/20°C (one trial’s setting) GrowPlants.org, Perilla plant growing guide Grower or shop guide 18 to 25°C preferred
Light hours	16 hours on, 8 off Updated to match the sources Was 14 hours on, 10 hours off before September 2026	Jacobs 1982, Comparison of Photoperiodic Sensitivity of Green-Leafed and Red-Leafed Perilla, Plant Physiology 70(1):303-306 (Princeton University) University or research P. crispa critical day length between 14 and 16 hours Lu, Takagaki et al. 2017, Growth and Accumulation of Secondary Metabolites in Perilla as Affected by PPFD and EC in a Plant Factory, Frontiers in Plant Science 8:708 University or research 16 h photoperiod
Light intensity (PPFD)	about 300 µmol/m²/s, especially for red shiso Partly backed Was Research tested 100, 200 and 300 µmol/m²/s before September 2026	Lu, Takagaki et al. 2017, Frontiers in Plant Science 8:708 University or research red perilla growth tracked PPFD; photosynthesis rose with PPFD in both
Light height	6 to 8 in House practice	No published source states this figure.
Germination	7 to 21 days dry, 4 to 7 after a 24-hour soak Partly backed Was 4 to 7 days if soaked 24 hours, 2 to 4 weeks if sown dry before September 2026	Johnny's Selected Seeds, Shiso Key Growing Information Seed company or maker 7 to 21 days; store seed in the freezer
Spacing	8 to 10 inches Backed by sources	University of Alaska Fairbanks Master Gardeners, Perilla (shiso) University or research thin to 8 to 12 inches Johnny's Selected Seeds, Shiso Key Growing Information Seed company or maker 6 to 12 inches
Plant height	18 to 30 inches unpinched, 12 to 18 kept pinched Partly backed Was 12 to 24 inches before September 2026	Johnny's Selected Seeds, Shiso Key Growing Information Seed company or maker 18 to 30 inches
Humidity	40 to 60% Partly backed	Lu, Takagaki et al. 2017, Frontiers in Plant Science 8:708 University or research 60 to 80% (one trial’s setting)
First harvest	8 to 10 weeks from seed Partly backed Was 6 to 8 weeks before September 2026	Lu et al. 2017, Frontiers in Plant Science 8:708 University or research 3 weeks seedling plus 5 weeks after transplant True Leaf Market, Shiso Seeds (Perilla) Green Seed company or maker 60 to 70 days

Spinach

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Cornell University CEA Program, Baby Spinach Handbook University or research 5.8 optimum; 5.6 to 6.0 acceptable Bostanci & Ulger 2022, Mediterranean Agricultural Sciences 35(1):7-14 (Akdeniz University) University or research 6.0 to 6.5
EC, seedling	1.0 to 1.2 Partly backed	Cornell University CEA Program, Baby Spinach Handbook University or research 1300 ± 100 µS/cm for the whole 14-day pond phase Grozine, Growing Hydroponic Spinach Grower or shop guide 1/8 to 1/4 strength (max 0.5) at first
EC, mature	1.4 to 1.8 Backed by sources	Bostanci & Ulger 2022, Mediterranean Agricultural Sciences 35(1):7-14 University or research 1.5 to 1.7 Cornell University CEA Program, Baby Spinach Handbook University or research 1.3 ± 0.1
Water temperature	59 to 68°F (15 to 20°C) Updated to match the sources Was 65 to 72°F (18 to 22°C) before September 2026	Cornell CEA Program, Baby Spinach Handbook University or research 50 to 68°F (15 to 20°C), chilled, to control Pythium New England Vegetable Management Guide (UMass Amherst and partner extensions), Spinach University or research optimum 55 to 60°F with about 12-hour days
Air temperature	60 to 70°F Backed by sources	University of Georgia Extension C1304, How to Grow Greenhouse Spinach During Georgia Summers Using Hydroponics University or research 60 to 77°F for growth Alto Garden, How to Grow Spinach with Hydroponics Grower or shop guide 60 to 68°F; stay under 78°F
Light hours	12 hours on, 12 off; baby leaf cut within about 3 weeks can run longer days Backed by sources Was 12 hours on, 12 hours off before September 2026	New England Vegetable Management Guide (UMass Amherst), Spinach University or research about 12 hours Cornell CEA Program, Baby Spinach Handbook University or research baby spinach: up to 24 hours, harvested 14 days after planting
Light intensity (PPFD)	300 to 400 µmol/m²/s, so the 12-hour day still reaches DLI 13 to 17 Updated to match the sources Was 200 to 300 µmol/m²/s at canopy before September 2026	Cornell CEA Program, Baby Spinach Handbook University or research at least 200 µmol; about 17 mol/m²/day Cornell CEA Program, Baby Spinach Handbook, set-points University or research 17 to 22 mol/m²/day
Light height	6 to 8 in House practice	No published source states this figure.
Germination	5 to 10 days Partly backed	Cornell CEA Program, Baby Spinach Handbook University or research 2 days in the germination area Seed Savers Exchange, Grow Spinach Seed company or maker 7 to 14 days
Spacing	4 to 6 inches between plants in a shared tote Backed by sources	University of Georgia Extension C1304, How to Grow Greenhouse Spinach During Georgia Summers Using Hydroponics University or research DWC holes 6 inches apart University of Maryland Extension, Growing Spinach in the Home Garden University or research thin to about 6 inches
Plant height	About 8 to 12 inches House practice	No published source states this figure.
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Cornell CEA Program, Baby Spinach Handbook, set-points University or research minimum 50, maximum 70%
First harvest	35 to 45 days Backed by sources	University of Georgia Extension C1304 University or research 2 to 3 weeks to transplant, harvest 3 to 4 weeks later Grozine, Growing Hydroponic Spinach Grower or shop guide about 5.5 weeks from seed

Stevia

Number	What the site says	Sources checked
pH	6.0 to 6.5 Partly backed Was 6.0 to 6.2 before September 2026	IGWorks, Growing Hydroponic Stevia Grower or shop guide 6.0 to 6.5 (table); 5.8 to 6.8 (text) Hydrilla, Hydroponics stevia Grower or shop guide 6.0 to 6.5
EC, seedling	1.0 House practice	No published source states this figure.
EC, mature	1.0 to 1.6 Partly backed	IGWorks, Growing Hydroponic Stevia Grower or shop guide 0.8 to 1.6; higher EC hurts flavour
Water temperature	65 to 75°F (18 to 24°C), house range. Air runs warmer at 68 to 82°F House practice Was 65 to 72°F (18 to 22°C), house range before September 2026	No published source states this figure.
Air temperature	68 to 82°F Partly backed	Gardyn, Grow Stevia At Home Grower or shop guide 60 to 75°F
Light hours	16 hours on, 8 off Updated to match the sources Was 14 hours on, 10 hours off before September 2026	NC State University, Stevia Breeding (Cucurbit Breeding programme) University or research short-day flowering; critical day length 8 to 14 h by variety Beemnet Mengesha Kassahun et al. 2014, Stevia Production Guideline, Ethiopian Institute of Agricultural Research University or research long days favour leaves; short days trigger blossoming
Light intensity (PPFD)	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Light height	6 to 8 in Partly backed	Gardyn, Grow Stevia At Home Grower or shop guide 6 to 12 inches
Germination	7 to 21 days, roughly half of seeds fail; press the seed onto the surface, do not cover, it needs light Backed by sources Was Difficult, roughly half of seeds fail before September 2026	NC State University, Stevia Breeding University or research seed needs light; will not germinate if covered Johnny's Selected Seeds, Stevia Key Growing Information Seed company or maker 7 to 21 days at 68 to 75°F
Spacing	8 to 12 inches Backed by sources	Beemnet Mengesha Kassahun et al. 2014, Stevia Production Guideline (EIAR) University or research 20 to 25 cm between plants Johnny's Selected Seeds, Stevia Key Growing Information Seed company or maker 12 inches
Plant height	12 to 18 inches pruned, up to 30 unpruned Backed by sources	Johnny's Selected Seeds, Stevia Key Growing Information Seed company or maker 18 to 30 inches
Humidity	40 to 60% House practice	No published source states this figure.
First harvest	2+ months Backed by sources	NC State University, Stevia Breeding University or research flowers 54 to 104 days after transplant IGWorks, Growing Hydroponic Stevia Grower or shop guide about 2 months

Strawberries

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research EC 1.8 to 2.2, pH 6 Barnett & Park, Effects of Root-Zone Temperature on Strawberry Growth (Arizona State University) University or research pH 5.8, EC 1.0 in DWC (one trial’s setting)
EC, seedling	1.0 to 1.2 Partly backed	NT Hydroponics, Hydroponic Strawberry Growing Guide Grower or shop guide 1.0 to 1.2 seedling
EC, mature	1.6 to 2.0 fruiting Partly backed Was 1.4 to 1.8 before September 2026	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 1.8 to 2.2 Illinois Extension, Hydroponic day-neutral strawberry production observations (2023) University or research about 1.8
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Barnett and Park, Effects of Root-Zone Temperature on Strawberry Growth and Fruit Quality (Arizona State University poster, 2026) University or research shoot mass rose from 18 to 24°C; 20°C gave larger, less sweet fruit
Air temperature	60 to 75°F Backed by sources	University of Minnesota Extension, Day-neutral strawberries University or research 45 to 85°F Drygair, Ideal Conditions for a Strawberry Greenhouse Seed company or maker 20 to 24°C days, 10 to 12°C nights
Light hours	16 hours on, 8 off Updated to match the sources Was 14 hours on, 10 hours off; fruiting crops may run to 16 before September 2026	Park, Sethi and Temnyk 2023, Growth, Flowering, and Fruit Production of Strawberry 'Albion' in Response to Photoperiod and PPFD of Sole-Source Lighting, Plants 12(4):731 (Arizona State) University or research 16 h raised fruit production 372 to 989% over 12 h Park, Sethi and Temnyk 2023, Plants 12(4):731 University or research 16 h brought flowering 17 to 21 days earlier
Light intensity (PPFD)	300 to 450 µmol/m²/s at 16 hours Partly backed Was 400 to 600 µmol/m²/s at canopy for good fruiting before September 2026	Park, Sethi and Temnyk 2023, Plants 12(4):731 University or research PPFD 200 to 450 raised growth but barely changed fruit Park, Sethi and Temnyk 2023, Plants 12(4):731 University or research 200 to 450 µmol raised crown and shoot growth
Light height	8 to 12 in Partly backed	Spider Farmer, Ultimate Guide for Hydroponic Strawberry Farming Seed company or maker 12 to 18 inches
Germination	Longer; not typical for apartment beginners Partly backed	No published source states this figure.
Spacing	8 to 12 inches between plants Backed by sources	University of Minnesota Extension, Day-neutral strawberries University or research 8 to 12 inches between plants
Plant height	10 to 18 inches tall including foliage and trusses Partly backed	No published source states this figure.
Humidity	50 to 70% with airflow Partly backed	Barnett and Park, Arizona State University poster (2026) University or research 72% RH
First harvest	60 to 90 days from bare-root plants or runners Backed by sources	University of Minnesota Extension, Day-neutral strawberries University or research plant mid-May, harvest from mid-July NT Hydroponics, Hydroponic Strawberry Growing Guide Grower or shop guide 60 to 90 days for everbearing

Sweet Basil

Number	What the site says	Sources checked
pH	5.5 to 6.5 Backed by sources	Oklahoma State University Extension, Electrical Conductivity and pH Guide for Hydroponics University or research 5.5 to 6.0 e-GRO Edible Alert 2018 (Cornell Cooperative Extension et al.), Magnesium Deficiency of Hydroponic and Container Grown Basil University or research target 5.8 (basil and lettuce columns of the target table)
EC, seedling	1.0 to 1.2 Partly backed Was 1.0 to 1.6 before September 2026	Oklahoma State University Extension, EC and pH Guide University or research 1.0 to 1.6 (all stages) Growth of Hydroponic Sweet Basil, Agriculture 2023, 13, 443 (Rutgers New Use Ag) University or research half strength for seedlings, full solution started at EC 1.7
EC, mature	1.0 to 1.6 Sources disagree Was 1.8 to 2.2 before September 2026	Oklahoma State University Extension, EC and pH Guide University or research 1.0 to 1.6 Ren et al. 2022, Horticulturae 8(3):216 University or research yield highest at 3.0; flavour compounds highest at 0.5 to 1.0 Wortman 2015, Scientia Horticulturae 194:34-42 University or research typical hydroponic EC 1 to 3; basil yield fell 44% at low EC
Water temperature	65 to 75°F (18 to 24°C); tolerates warmer aerated water, up to about 80°F (27°C) Sources disagree Was 65 to 72°F (18 to 22°C) before September 2026	Hendrickson, Dunn, Goad, Singh et al. 2022, Effects of Elevated Water Temperature on Growth of Basil Using Nutrient Film Technique, HortScience 57(8):925 (Oklahoma State University) University or research 27.5°C (81°F) water recommended for most cultivars Hendrickson, Dunn, Goad, Singh et al. 2022, Effects of Elevated Water Temperature on Growth of Basil Using Nutrient Film Technique, HortScience 57(8):925 (Oklahoma State University) University or research cooler water held more oxygen but did not grow more basil Walters and Currey 2018, HortScience 53(9):1319-1325 (Univ. of Tennessee, Iowa State) University or research solution held at 22.1°C (71.8°F) (one trial’s setting)
Air temperature	65 to 75°F Backed by sources	Ren et al. 2022 and PMC9311585 (basil plant-factory trials) University or research 24°C day / 21°C night (75/70°F) (one trial’s setting) Growth of Hydroponic Sweet Basil, Agriculture 2023 (Rutgers) University or research 23 to 26°C (73 to 79°F)
Light hours	14 hours on, 10 hours off Backed by sources	Johnny's Selected Seeds, Hydroponic & Container Basil Guide Seed company or maker minimum 14 hours per day Growth of Hydroponic Sweet Basil, Agriculture 2023, 13, 443 (Rutgers) University or research 16 h photoperiod (one trial’s setting)
Light intensity (PPFD)	200 to 400 µmol/m²/s (DLI 12 or more); more light, up to about 500, still adds yield Backed by sources Was 200 to 400 µmol/m²/s before September 2026	Growth of Hydroponic Sweet Basil, Agriculture 2023, 13, 443 (Rutgers) University or research optimum 224 µmol/m²/s Beaman, Gladon, Schrader 2009, HortScience 44(1):64-67, Sweet Basil Requires an Irradiance of 500 µmol for Greatest Edible Biomass Production University or research yield least at 300, greatest at 500 to 600
Light height	6 to 8 in House practice	No published source states this figure.
Germination	3 to 7 days in a warm room (70°F or more), up to 2 weeks if cooler. Pre-soaking 24 hours speeds it slightly Partly backed Was 3 to 7 days before September 2026	University of Illinois Extension, Herbs: Basil University or research 5 to 7 days, media 70°F or more Ren, Lu, Xu, Zhuang et al. 2022, plant factory basil, Biology 11(7):991 (PMC9311585) University or research 48 h at 20°C
Spacing	6 to 8 inches in a shared tote Partly backed	Purdue Extension HO-189, Sweet Basil: A Production Guide University or research 6 inches in the row; beds 12 x 12 Utah State University Extension, How to Grow Basil in Your Garden University or research final stand 12 inches
Plant height	12 to 18 inches unpruned; keep to 10 with regular topping Partly backed Was 12 to 14 inches unpruned before September 2026	University of Illinois Extension, Herbs: Basil University or research 12 to 18 inches tall
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Ren, Lu, Xu, Zhuang et al. 2022, plant factory basil, Biology 11(7):991 (PMC9311585) University or research 65 to 80% (one trial’s setting) Growth of Hydroponic Sweet Basil, Agriculture 2023, 13, 443 (Rutgers) University or research 20 to 40% recorded; plants grew
First harvest	5 to 6 weeks from seed Updated to match the sources Was 3 to 4 weeks before September 2026	Ren et al. 2022, Horticulturae 8(3):216 University or research harvested 34 days after sowing (18 days after transplant) PMC9311585 (basil plant-factory trial) University or research transplant at 20 days after sowing, harvest 20 days later (40 days from seed)

Swiss Chard

Number	What the site says	Sources checked
pH	5.5 to 6.8 Backed by sources	Singh & Dunn 2019, Fertilizer and Cultivar Selection of Lettuce, Basil, and Swiss Chard for Hydroponic Production, HortTechnology (Oklahoma State University) University or research EC 1.5 to 2.5, pH 5.5 to 6.5 (one trial’s setting) Salve Regina University Hydroponic Center, Bright Lights Swiss Chard Hydroponic Grow Guide University or research 6.0 to 6.5
EC, seedling	0.8 to 1.0 House practice	No published source states this figure.
EC, mature	1.8 to 2.3 Backed by sources	Singh & Dunn 2019, HortTechnology (Oklahoma State University) University or research 1.5 to 2.5 IGWorks, Growing Hydroponic Swiss Chard Grower or shop guide 1.8 to 2.3
Water temperature	65 to 75°F (18 to 24°C), house range Partly backed Was 65 to 72°F (18 to 22°C), house range before September 2026	Lanitex Hydro Garden, Grow Chard (Australia) Grower or shop guide 18 to 22°C (65 to 72°F)
Air temperature	55 to 75°F Backed by sources	Utah State University Extension, How to Grow Swiss Chard in Your Garden University or research best at or below 75°F Johnny's Selected Seeds, Swiss Chard Key Growing Information Seed company or maker prolonged low 50s can cause bolting
Light hours	14 hours on, 10 hours off Partly backed	No published source states this figure.
Light intensity (PPFD)	150 to 300 µmol/m²/s (leafy green category). Not documented per species Partly backed	Singh, Dunn, Payton and Brandenberger 2019, Fertilizer and Cultivar Selection of Lettuce, Basil, and Swiss Chard for Hydroponic Production, HortTechnology 29(1):50-56 (Oklahoma State) University or research average DLI 14.9
Light height	6 to 8 in House practice	No published source states this figure.
Germination	5 to 14 days Backed by sources Was Up to 2 weeks before September 2026	Utah State University Extension, Swiss Chard in the Garden University or research 7 to 14 days at 55 to 75°F; above 80°F reduces germination Seed Savers Exchange, Grow Swiss Chard Seed company or maker 5 to 10 days
Spacing	6 to 8 inches in towers, 8 to 12 in beds Backed by sources	Utah State University Extension, Swiss Chard in the Garden University or research 6 inches in the row Singh, Dunn, Payton and Brandenberger 2019, HortTechnology 29(1):50-56 University or research NFT holes 8 inches on centre
Plant height	12 to 24 inches Partly backed	University of Wisconsin-Madison Extension, Swiss Chard University or research 'Fordhook Giant' 24 to 28 inches
Humidity	50 to 70% Partly backed Was 45 to 55% before September 2026	Lanitex Hydro Garden, Grow Chard (Australia) Grower or shop guide 50 to 70%
First harvest	about 5 weeks Backed by sources	University of Wisconsin Extension, Swiss Chard University or research leaves from about 4 weeks IGWorks, Growing Hydroponic Swiss Chard Grower or shop guide about 5 weeks

Tarragon

Number	What the site says	Sources checked
pH	6.0 to 6.5 Backed by sources	NC State University, French Tarragon as a Commercial Herb Crop (2004 report) University or research hydroponic perlite at 1200 ppm, pH 6.3 Performance on nutritive solution utilization by Tarragon (Artemisia dracunculus) cultivated in hydroponic (Brazil) University or research 5.5 to 6.5
EC, seedling	about 1.0 Filled from sources	IGWorks, Growing Hydroponic Tarragon Grower or shop guide about 1.0 while young
EC, mature	1.0 to 1.8 Partly backed	IGWorks, Growing Hydroponic Tarragon Grower or shop guide 1.0 to 1.8 LaNiTex Hydro Garden, Cultivate Tarragon in Hydroponic Systems Grower or shop guide 1.5 to 2.5
Water temperature	65 to 75°F (18 to 24°C), with aeration above 72°F (site-wide rule) House practice Was 65 to 72°F (18 to 22°C) before September 2026	No published source states this figure.
Air temperature	65 to 75°F Filled from sources	Utah State University Extension, How to Grow French Tarragon University or research warm but not hot; shade above 90°F LaNiTex Hydro Garden, Cultivate Tarragon in Hydroponic Systems Grower or shop guide 18 to 25°C
Light hours	no crop-specific exception documented, so the general 14 hours on, 10 Partly backed	No published source states this figure.
Light intensity (PPFD)	200 to 400 µmol/m²/s (woody herb band) House practice	No published source states this figure.
Light height	Not documented Not documented	Nothing reliable was found, so the site gives no figure.
Germination	Not applicable. French tarragon cannot be started from seed Backed by sources	Utah State University Extension, French Tarragon in the Garden University or research French tarragon from cuttings or divisions, not seed
Spacing	about 10 inches (25 cm) in a hydroponic channel; 24 inches if left to full size Filled from sources	de Oliveira et al. 2023, Performance on nutritive solution utilization by Tarragon (Artemisia dracunculus L.) cultivated in hydroponic, Scientia Plena 19(8) University or research 25 cm between holes Utah State University Extension, French Tarragon in the Garden University or research 24 inches
Plant height	2 to 3 feet for French tarragon in soil Backed by sources	Utah State University Extension, French Tarragon in the Garden University or research 24 to 36 inches tall, 12 to 15 inch spread
Humidity	50 to 70% (site-wide range) Partly backed Was 40 to 70% before September 2026	Lanitex Hydro Garden, Grow Tarragon (Australia) Grower or shop guide 40 to 70%
First harvest	4 to 6 weeks from a cutting or division Backed by sources	NC State University, French Tarragon as a Commercial Herb Crop (2004 report) University or research harvest size in 5 weeks hydroponically Utah State University Extension, How to Grow French Tarragon University or research first harvest 6 to 8 weeks after growth begins

Thyme

Number	What the site says	Sources checked
pH	5.5 to 6.5 Partly backed	LetPot, How to grow thyme hydroponically Grower or shop guide 5.5 to 6.5 Grow With Hydroponics, Hydroponic Thyme guide Grower or shop guide 5.8 to 6.3; soil 6.0 to 8.0 does not carry over
EC, seedling	1.0 to 1.2 House practice	No published source states this figure.
EC, mature	1.2 to 1.6 Partly backed	Grow With Hydroponics, Hydroponic Thyme guide Grower or shop guide 1.0 to 1.6; no thyme trial exists IGWorks, Growing Hydroponic Thyme Grower or shop guide 0.8 to 1.6
Water temperature	65 to 75°F (18 to 24°C) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Comparative study on the growth and development of thyme and basil herbs in aquaponic system and hydroponic system University or research optimum 20 to 25°C for basil and thyme
Air temperature	65 to 75°F Partly backed	Cretu et al. 2022, Scientific Papers Series D Animal Science 65(1) University or research 20 to 25°C optimum LetPot, How to grow thyme hydroponically Grower or shop guide 20 to 25°C
Light hours	14 hours on, 10 hours off Backed by sources	Tabbert et al. 2021, Increased Plant Quality, Greenhouse Productivity and Energy Efficiency with Broad-Spectrum LED Systems: A Case Study for Thyme, Plants 10(5):960 University or research 14 h supplemental lighting; 16 h to reach the DLI target in winter Comparative study on thyme and basil in aquaponic and hydroponic systems University or research 12 hours (one trial’s setting)
Light intensity (PPFD)	350 to 400 µmol/m²/s (DLI 18 or more) Partly backed Was 200 to 400 µmol/m²/s before September 2026	Tabbert et al. 2021, Increased Plant Quality, Greenhouse Productivity and Energy Efficiency with Broad-Spectrum LED Systems: A Case Study for Thyme, Plants 10(5):960 University or research thyme needs DLI 18 or more Currey and Litvin (Iowa State University), Hydroponic production primer: Improve culinary herb yields, Produce Grower, August 2019 Trade press thyme fresh weight rises linearly to DLI 20; high or very high light crop
Light height	4 to 6 in House practice	No published source states this figure.
Germination	14 to 21 days; surface-sow, do not cover, thyme seed needs light Backed by sources	Johnny's Selected Seeds, Summer Thyme Seed company or maker 14 to 21 days at 65 to 70°F Baker Creek Heirloom Seeds, Wild Thyme Seed company or maker 14 to 28 days; surface-sow, needs light
Spacing	6 inches Backed by sources	Johnny's Selected Seeds, Summer Thyme Seed company or maker 6 to 8 inches
Plant height	6 to 10 inches, trailing Partly backed	No published source states this figure.
Humidity	50 to 70%, tolerates the lower end better than most Partly backed Was 40 to 70%, tolerates the lower end better than most before September 2026	Tabbert et al. 2021, Increased Plant Quality, Greenhouse Productivity and Energy Efficiency with Broad-Spectrum LED Systems: A Case Study for Thyme, Plants 10(5):960 University or research average 38.8 to 47.2% RH
First harvest	10 to 13 weeks from seed, 4 to 6 weeks from a cutting Partly backed Was 8 to 10 weeks before September 2026	Johnny's Selected Seeds, Summer Thyme Seed company or maker 90 to 95 days from seeding Baker Creek Heirloom Seeds, Thyme Seeds, Wild Seed company or maker 75 to 90 days

Watercress

Number	What the site says	Sources checked
pH	6.5 to 7.0 Partly backed	Utah State University Extension, How to Grow Watercress in Your Garden University or research 6.5 to 7.5 IGWorks, Growing Hydroponic Watercress Grower or shop guide 6.5 to 7.0
EC, seedling	1.0 to 1.2 Partly backed	Rise Gardens, Growing Watercress Hydroponically at Home Grower or shop guide low end of 0.4 to 1.8 for seedlings
EC, mature	1.5 to 2.0 Backed by sources	Kratky, Maehira & Cupples 2002, Shading and periodic replacement of nutrient solution improve production of hydroponically-grown watercress (University of Hawaii) University or research EC 1.0 to 1.8 Kratky 2015, Growing Direct-Seeded Watercress by Two Non-Circulating Hydroponic Methods, UH-CTAHR VC-7 University or research EC 1.7 to 2.5 (floating cover method)
Water temperature	65 to 70°F (18 to 21°C); keep it under 78°F, deeper covered containers stay cooler Backed by sources Was 65 to 70°F (18 to 21°C) before September 2026	B.A. Kratky, University of Hawaii CTAHR VC-7, Growing Direct-Seeded Watercress by Two Non-Circulating Hydroponic Methods University or research above 78°F is detrimental CTAHR, Shading and periodic replacement of nutrient solution improve production of hydroponically-grown watercress University or research solution stayed at or below 18°C (64°F) in summer
Air temperature	60 to 70°F Backed by sources	Utah State University Extension, How to Grow Watercress in Your Garden University or research flavour worse above 85°F Rise Gardens, Growing Watercress Hydroponically at Home Grower or shop guide 50 to 75°F
Light hours	14 hours on, 10 hours off Partly backed	Breeding indoor watercress for enhanced crop biofortification (PMC12226469, 2025) University or research 18 h at 220 µmol, DLI 14.26 (one trial’s setting) Palaniswamy and McAvoy 2001, Watercress: A Salad Crop with Chemopreventive Potential, HortTechnology University or research long (16 h) days raised gluconasturtiin 30 to 40% over short (8 h)
Light intensity (PPFD)	150 to 250 µmol/m²/s (low-medium) Partly backed	Watercress grown in UK, California and an indoor vertical farm (Scientia Horticulturae 2022, S0304423822001935) University or research 220 µmol Breeding indoor watercress for enhanced crop biofortification (PMC12226469, 2025) University or research 220 µmol
Light height	6 to 8 in House practice	No published source states this figure.
Germination	2 to 4 days at room temperature (68°F or more), up to 10 days when cold Partly backed Was 5 to 10 days before September 2026	B.A. Kratky, University of Hawaii CTAHR VC-7 University or research 2 to 4 days at 68 to 95°F; 10 days at 48°F Baker Creek Heirloom Seeds, How To Grow Watercress Seed company or maker 7 to 14 days at 50 to 60°F
Spacing	8 inches between plants, or one net pot sown with a pinch of seed about every 12 inches Updated to match the sources Was 4 to 6 inches between plants before September 2026	Utah State University Extension, Watercress in the Garden University or research 8 inches B.A. Kratky, University of Hawaii CTAHR VC-7 University or research 1.5 net pots per square foot, 10 to 20 seeds per pot
Plant height	6 to 10 inches, sprawling habit Partly backed	Rise Gardens, Growing Watercress Hydroponically at Home Grower or shop guide first harvest at 4 to 6 inch stems
Humidity	50 to 70% Partly backed Was 40 to 70% before September 2026	Breeding indoor watercress for enhanced crop biofortification (PMC12226469, 2025) University or research 50 to 70%
First harvest	5 to 7 weeks from seed Partly backed Was 6 to 8 weeks before September 2026	Kratky 2015, UH-CTAHR VC-7 University or research 3 to 5 weeks from transplanting Rise Gardens, Growing Watercress Hydroponically at Home Grower or shop guide 25 to 35 days from seed

Wheatgrass

Number	What the site says	Sources checked
pH	6.0 to 7.0 Partly backed	Wheatgrass (Triticum aestivum) growth and nutrient content irrigated with aquaculture process water (PMC12274266) University or research control tank pH-controlled at 6.5 (one trial’s setting) IGWorks, Growing Hydroponic Wheatgrass Grower or shop guide 6.0 to 7.0
EC, seedling	0.8 to 1.2 Partly backed	IGWorks, Growing Hydroponic Wheatgrass Grower or shop guide 0.8 to 1.2
EC, mature	0.8 to 1.2 Partly backed	IGWorks, Growing Hydroponic Wheatgrass Grower or shop guide 0.8 to 1.2 Wheatgrass growth and nutrient content irrigated with aquaculture process water (PMC12274266) University or research control EC about 1630 µS/cm (one trial’s setting)
Water temperature	65 to 75°F (18 to 24°C), with aeration above 72°F (site-wide rule) Partly backed Was 65 to 72°F (18 to 22°C) before September 2026	Hydroponic and aquaponic wheatgrass trial (PMC12274266, 2025) University or research NFT reference 23°C; trial about 25°C with no heat stress (one trial’s setting)
Air temperature	65 to 75°F Partly backed	Wheatgrass growth and nutrient content irrigated with aquaculture process water (PMC12274266) University or research average air 22.7°C (one trial’s setting)
Light hours	14 hours on, 10 hours off. Sources give 12 to 16 Partly backed	Hydroponic wheatgrass fertiliser study, Plants 2025, 14(14), 2166 (MDPI) University or research 12 h at 250 µmol (one trial’s setting) Chalil et al. 2022, antioxidants of wheatgrass microgreens under LED combinations, 3Bio Journal of Biological Science, Technology and Management 4(1):26-34 (ITB) University or research 12 h light, 12 h dark for 10 days (one trial’s setting)
Light intensity (PPFD)	120 to 250 µmol/m²/s (microgreen category) Partly backed	Hydroponic wheatgrass fertiliser study, Plants 2025, 14(14), 2166 (MDPI) University or research 250 µmol
Light height	6 to 12 in House practice	No published source states this figure.
Germination	2 to 7 days Backed by sources	Chalil et al. 2022, antioxidants of wheatgrass microgreens under LED combinations, 3Bio Journal of Biological Science, Technology and Management 4(1):26-34 (ITB) University or research 3 days in a dark room to germinate IGWorks, Growing Hydroponic Wheatgrass Grower or shop guide 2 to 7 days
Spacing	Not applicable. Sown densely Backed by sources	No published source states this figure.
Plant height	6 to 8 inches Partly backed	Hydroponic and aquaponic wheatgrass trial (PMC12274266, 2025) University or research shoot length about 20 to 24 cm
Humidity	40 to 60%. Higher raises mould risk on dense mats Backed by sources	Chalil et al. 2022, antioxidants of wheatgrass microgreens under LED combinations, 3Bio Journal of Biological Science, Technology and Management 4(1):26-34 (ITB) University or research ideal 40 to 50%, 18 to 26°C Hydroponic wheatgrass fertiliser study, Plants 2025, 14(14), 2166 (MDPI) University or research controlled below 60%
First harvest	7 to 14 days Partly backed Was 2 to 3 weeks before September 2026	Wheatgrass growth and nutrient content irrigated with aquaculture process water (PMC12274266) University or research ended 12 days after sowing Modern Hippie Habits, Growing Wheatgrass Grower or shop guide 7 to 10 days

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If you know a university, extension or peer-reviewed source that covers one of these numbers better, or one marked house practice, please send it through the contact page. A better source changes the number here, in every post that uses it and in the calculators. How products are chosen and labelled is on the how we test page.