Hydroponic pH and EC Chart: Targets for 39 Herbs, Greens and Fruiting Crops

Disclosure: As an Amazon Associate, Urban Hydro Space earns from qualifying purchases at no extra cost to you. This post contains affiliate links. Thank you for supporting Urban Hydro Space!

🔎 Researched, not tested: every product in this post was chosen from the makers’ published specifications, labels and listings, not tried at home. How we research and choose products.

This hydroponic pH and EC chart gives the targets for 39 herbs, leafy greens, fruiting crops and tray crops, grouped the way you actually grow them, with the PPM your meter will show on both common scales. Every figure comes from the same crop table the rest of this site uses, so each one traces back to a published source, from university trials and extension guides to seed company growing notes.

Why another chart? Because most of the ones online disagree with each other, and some are years out of date. Many still list basil well above EC 2.0, a figure the newer university trials don’t support. Others give PPM without saying which scale they mean, so a reader with a 700-scale pen who follows a 500-scale chart underfeeds every plant by almost a third. Make the reverse mistake and you overfeed by 40 percent instead. If you are still choosing a system, the complete guide to apartment hydroponics starts at the beginning. This page is for the moment you have a meter in your hand and a jar in front of you.

How to Read This pH and EC Chart

Each row has five numbers. The pH range is where the roots can take up every nutrient; outside it, food sits in the water and the plant starves anyway. Seedling EC is the strength to use until young plants are established. Mature EC applies when the plant is established and growing fast.

What the PPM Columns Mean

The last two columns turn the mature EC into PPM. Meters calculate PPM from the EC reading with a conversion factor, but brands use different ones. A 500-scale meter multiplies the EC by 500, while a 700-scale meter multiplies it by 700. Check your meter’s manual before you trust a PPM figure from anyone, including this page. If your meter shows EC, use EC. It also means the same thing on every meter in the world.

Where a seedling cell says start at 1.0, the research gives no seedling figure for that crop. The table uses the gentle strength this site starts every seedling at instead.

The Full Hydroponic pH and EC Chart

The chart is split into four groups, because that is how crops end up sharing water in a real apartment. Tap a crop’s name to open its full growing guide where one exists. For the research behind any single figure, the crop sources page lists it crop by crop.

Herbs

Herbs are where most apartment growers start, and they are also where the old charts are most wrong. Still, most of them sit happily between EC 1.0 and 1.8. Mint is the outlier.

Basil in Winter, and Why Mint Stands Apart

Two notes on this group. Basil can go a little stronger in winter, so raise it toward 1.8 when the days are short. And mint really does want that much. It is the one herb that sulks at the strength that suits basil, which is why it rarely thrives in a shared tank.

Leafy Greens

Greens split into two camps. Lettuce and mizuna are light eaters, so they burn easily. Chard, kale and mustard greens, however, will take far more.

Butterhead is the gentlest feeder of the greens. Its range starts at 0.8 and tops out at 1.4, level with loose-leaf lettuce. If the outer leaves of a butterhead start to crisp at the edges while everything else looks fine, the tank is too strong for it.

Fruiting Crops and Edible Flowers

Fruit takes food. Tomatoes and peppers run the strongest solutions on this page, and the flowers sit much lower because rich feeding gives them leaves instead of blooms.

The strawberry figure is for plants in fruit, so younger plants start at the seedling figure instead. Peas are fed normally too, because in a clean hydroponic system there are no root bacteria to fix nitrogen for them, so they need it from the bottle like everything else.

Microgreens and Tray Crops

Tray crops are cut young, so they need very little. They start on the weakest feed on this page and step up only slightly once the leaves turn green.

For microgreens, the “mature” column means once the seedlings are green, since the whole crop is harvested at 7 to 14 days.

The Crops That Break the Usual Rules

Most charts give one pH range for everything and then move on. That works for 29 of these 39 crops. The other ten are where a “5.5 to 6.5” rule quietly lets you down, so they are worth learning by name.

Crops That Want a Higher pH

Watercress is the only crop on this page that needs the reservoir above 6.5. Hold it at 6.5 to 7.0. Three more have ranges that reach 7.0 and do best high in them:

• Nasturtium, range 6.0 to 7.0, best at 6.5 to 6.8
• Lemongrass, range 6.0 to 7.0, with 6.3 to 6.5 as the target
• Bok choy, 6.0 to 7.0

Six others tolerate a pH above 6.5 but grow perfectly well inside the standard range: Swiss chard, wheatgrass, micro herbs, romaine, butterhead and mustard greens. So you don’t need to chase a higher number for them.

Crops That Only Like the Top Half

This group catches people out. Chives, cilantro, garlic chives, tarragon and stevia all want 6.0 to 6.5, while pea pods want 6.2 to 6.5 and celery 6.3 to 6.5. A tank held at 5.6 is inside the “normal” range and still too acidic for every one of them. So if your chives look pale and slow while the basil beside them is fine, check this first.

Two crops, however, sit at the other end. Dwarf cucumber wants 5.5 to 6.0 and dwarf peppers 5.8 to 6.3, so a reservoir that has drifted up to 6.4 is already too high for both. If your pH climbs every few days, why hydroponic pH keeps drifting explains what pushes it.

Seedlings That Start Below 1.0

This site starts most seedlings at EC 1.0. That is a deliberately gentle house choice, since published stage tables often start lower. Eight crops have documented seedling figures below it:

• Microgreens at 0.5 to 1.0, and wheatgrass at 0.8 to 1.2
• Swiss chard, lemongrass, shiso, nasturtium and mizuna at 0.8 to 1.0
• Lemon balm, 0.8 to 1.1

Heavy Eaters and Light Eaters

When you sort the mature EC column, the crops fall into three bands. The heavy eaters have ranges that climb past 2.0: mint, cherry tomatoes, dwarf peppers, lemongrass, dwarf cucumber, Swiss chard, mustard greens and celery. The light eaters top out at 1.4 or below: loose-leaf and butterhead lettuce, plus the three tray crops. Everything else sits in the middle band, which is why the middle is where a mixed tank lives. For herbs in particular, the EC guide for hydroponic herbs goes deeper on reading nutrient strength.

EC to PPM: Why Your Meter Shows a Different Number

A meter never measures PPM. It measures how well the water carries an electric current, which rises as more dissolved salt goes in, and then it multiplies that reading by a factor to show you a PPM estimate. The two common factors are 500 and 700. Neither is wrong. They are simply different conventions, the way Fahrenheit and Celsius both describe the same room.

The trouble starts when a chart doesn’t say which one it used. Here is the same water on both scales:

For example, look at the 1.5 row. A 700-scale chart that says “run 1,050 PPM” means exactly the same water as a 500-scale chart that says 750. Follow the wrong one and you either starve the plants or push them toward burn, and the meter never warns you.

My advice is flat: switch the meter to EC and leave it there. EC needs no conversion, so it needs no footnote either. If your pen can only show PPM, find its scale in the manual once, write it on a piece of tape on the pen, and read the matching column above. A pen that reads EC directly avoids the whole problem, and my EC meter roundup compares the ones worth buying for small reservoirs.

Running Several Crops on One Reservoir

A single tank feeding several plants is where most apartment setups end up, and it works once you accept a compromise. Run it at EC 1.5 and a pH near 6.0. That pH sits inside the range of 36 of the 39 crops in the chart.

The three that don’t fit are watercress, pea pods and celery, which all want the water higher than 6.0. Give them their own container instead. The same goes for the heavy eaters: mint at 1.5 is underfed, and tomatoes or peppers at 1.5 grow leaves and very little fruit.

At the other end, lettuce is fed a little above its own range at 1.5. It rarely burns, but watch the outer leaves for crisp brown edges, which mean the tank is too strong for it. A proven combination is lettuce, arugula, basil and parsley together; the one-reservoir salad plan shows how to lay one out, and growing arugula, kale and spinach together covers a greens-only tank.

How to Hit the Numbers in a Jar or Bucket

Knowing the target is half the job. Getting a quart jar to sit on it is the other half, and small volumes swing fast. The order matters more than anything:

1. Read the water first. Tap water already carries some minerals, so measure its EC and pH before a drop of nutrient goes in. Using tap water for hydroponics explains what to do if yours starts high.
2. Add the nutrients and stir. With a two-part feed, add each part separately and stir between them, as described in how to mix two-part nutrients.
3. Measure the EC. Too low, add a little more feed. Too high, add plain water.
4. Adjust the pH last. Nutrients shift the pH as they dissolve, so any pH correction made before feeding is wasted.

Keeping It There Between Changes

After that, maintenance depends on the system. In an aerated bucket or any pumped system, top off daily with plain pH-adjusted water, never with more nutrients, and change the whole reservoir every 2 weeks; how often to change hydroponic water has the full routine. The EC creeps up between changes because the plants drink water faster than they use food. A Kratky jar, however, is different. It is sized to last the crop and never refilled to the brim, and if a long crop runs low late on, add a little nutrient solution, no more than about an inch.

The Feed Matters Less Than You Think

The feed itself matters less than people think, as long as it is a complete hydroponic formula and not a soil fertilizer, which does not dissolve or balance correctly in water. If you haven’t settled on one, the best hydroponic nutrients for small systems narrows it down to a few that are easy to dose in a jar.

When Your Plants Disagree With the Chart

Charts describe a typical plant in a typical setup. Your basil, however, hasn’t read this one. When the leaves tell you something is wrong even though the meter says you are on target, work through the checks in this order:

Notice where pH sits in that list. Out-of-range pH locks nutrients out even when the EC reads perfectly, so a pale plant is a pH question before it is a feeding question. So adding more fertilizer to a locked-out plant only raises the EC and makes the next problem worse. Why hydroponic leaves turn yellow walks through the diagnosis step by step.

When the EC Runs Too High

If the EC has run too high, don’t dump the whole tank in a panic. Lowering EC in a small system shows how to bring it down gently instead. And if the chart and the plant still disagree after that, calcium and magnesium are the usual suspects, especially with soft or filtered water; whether you need Cal-Mag explains when it helps and when it is money wasted.

After a hard cut or any stress, ease the plant back in. Hold the EC at 1.2 to 1.5 for 4 to 7 days before returning to its normal range. And to plan when each crop will be ready once the numbers are right, the seed-to-harvest calculator works it out from your sowing date.

One Last Tip

When a plant looks wrong, change one number at a time. It is tempting to raise the EC, nudge the pH and move the light on the same evening, and if the plant then recovers you have learned nothing, because you can’t tell which change did it. Next time you will be guessing again. Pick the most likely cause from the table above, fix only that, write down what you changed and the date, and judge the result by the new growth rather than the old leaves. It is slower by a few days and much faster over a year.

Frequently Asked Questions

What is the best pH for hydroponics?

For most herbs and leafy greens, keep the pH between 5.5 and 6.5, and hold a mixed tank near 6.0. Watercress is the exception and needs 6.5 to 7.0. Chives, cilantro, stevia and tarragon only like the top half, 6.0 to 6.5, while dwarf cucumber prefers 5.5 to 6.0.

What EC should hydroponic plants be at?

Most mature herbs and greens grow well between EC 1.0 and 1.8. Lettuce sits low at 1.0 to 1.4, while mint wants 2.0 to 2.4 and cherry tomatoes and peppers 2.0 to 2.5. Start seedlings gently at about 1.0, and run a shared tank at 1.5.

How do I convert EC to PPM?

Multiply the EC by your meter’s conversion factor. A 500-scale meter shows EC 1.5 as 750 PPM, and a 700-scale meter shows the same water as 1,050 PPM. Check the manual to learn which scale yours uses, or switch the meter to EC and skip the conversion entirely.

What PPM is best for hydroponic herbs?

It depends on the meter’s scale. Basil at EC 1.0 to 1.6 reads 500 to 800 PPM on a 500-scale meter and 700 to 1,120 PPM on a 700-scale meter. Parsley, dill and oregano run a little higher, at EC 1.4 to 1.8, which is 700 to 900 or 980 to 1,260 PPM.

Which plants need a higher pH in hydroponics?

Watercress needs 6.5 to 7.0, the only crop here that wants the reservoir above 6.5. Nasturtium does best at 6.5 to 6.8, lemongrass at 6.3 to 6.5, and bok choy grows across 6.0 to 7.0. Pea pods and celery also want the water above 6.0, at 6.2 to 6.5 and 6.3 to 6.5.

Can different plants share the same nutrient solution?

Yes, if their needs overlap. Run a mixed tank at EC 1.5 and a pH near 6.0, which suits 36 of the 39 crops in this chart. Give heavy eaters like mint, tomatoes and peppers their own container, along with watercress, pea pods and celery, which want a higher pH.

What EC should hydroponic seedlings be at?

Start most seedlings at about EC 1.0 and raise it as they establish. A few crops start lower: microgreens at 0.5 to 1.0, Swiss chard, lemongrass, shiso, nasturtium and mizuna at 0.8 to 1.0, and lemon balm at 0.8 to 1.1. Strong feed burns tender new roots quickly.

Should I adjust pH or EC first?

Adjust EC first and pH last. Measure the plain water, add and stir the nutrients, check the EC, and only then correct the pH. Nutrients change the pH as they dissolve, so a pH correction made before feeding has to be done again anyway.

Why does my plant look hungry when the EC is right?

The pH is usually out of range. When the pH drifts too high or too low, roots can’t take up nutrients that are sitting right there in the water, so the plant yellows as if it were starving. Correct the pH toward 6.0 before you add any more feed.

How often should I change the nutrient solution?

In a bucket, tote or pumped system, top off daily with plain pH-adjusted water and change the whole reservoir every 2 weeks. A Kratky jar works differently: size it to last the crop, and never refill it to the brim. Late on, add at most about an inch of nutrient solution.

Happy growing! 🌿
Sarah, Urban Hydro Space