Hydroponic edible flowers bring color to an indoor garden that is otherwise all green. Nasturtiums give peppery orange and red blooms, along with leaves and even young seeds you can eat, and calendula gives golden petals for salads, soups and tea. Both grow well in water, both are rated Easy, and both flower within about 6 to 8 weeks of sowing.
They are not twins, though, and treating them the same is the most common mistake. Nasturtium wants a higher pH and 16 hours of light, while calendula wants a lower pH and the usual 14 hours, so they do not share a tank or a timer. And both share one trap: feed them like leafy herbs, with plenty of nitrogen, and you get lush leaves and hardly any flowers. This guide covers each flower on its own terms. If hydroponics is new to you, start with the apartment hydroponics beginner’s guide.
Hydroponic Edible Flowers at a Glance
Key takeaways
- Nasturtium and calendula need different pH and light, so grow them in separate containers under separate timers.
- Keep the feed modest. Too much nitrogen or a high EC gives lush leaves and few flowers, the defining mistake with both.
- Nasturtium: pH 6.0 to 7.0, EC 1.0 to 1.6, 16 hours of light at 300 PPFD or more. Choose compact bush types.
- Calendula: pH 5.5 to 6.2, EC 1.2 to 1.8, 14 hours of light, and keep the air moving so buds do not rot.
- First flowers come about 6 to 8 weeks from seed. Pick often, since regular picking keeps more buds coming.
The Two Flowers Side by Side
Every figure here comes from the crop table this site uses, and times count from sowing.
| Setting | Nasturtium | Calendula |
|---|---|---|
| pH | 6.0 to 7.0, since it prefers a higher band than most crops | 5.5 to 6.2, target 5.8 to 6.2 |
| Feed strength (EC) | 0.8 to 1.0 seedling, and later 1.0 to 1.6 | 1.2 seedling, and later 1.2 to 1.8 |
| Light | 16 hours on, 8 off, because longer days give more leaf and flowers | 14 hours on, 10 off, like most herbs |
| Light intensity | At least 300 PPFD, since more light gives more leaf | Not documented; small flowering plants usually sit at 250 to 400 |
| Water temperature | 55 to 75°F (13 to 24°C), although cooler suits it better | 64 to 75°F (18 to 24°C), while warm damp air rots buds |
| Room | 55 to 75°F, humidity 50 to 70 percent, better when cool | 64 to 75°F, with airflow, because damp heat rots buds |
| Germination | 7 to 10 days; bury the seed half an inch, as it needs darkness | 7 to 14 days at about 70°F; cover the seed, since light slows it |
| Container | Kratky in 1 gallon for bush types, or DWC of 1 to 2 gallons | DWC of 1 to 2 gallons, while Kratky is only marginal |
| First harvest | Leaves at about 4 weeks, but flowers at 6 to 8 weeks | First flowers at 6 to 8 weeks, too |
Why These Two Grow Apart
It is tempting to put both flowers in one tote under one light. They clash on the two settings that matter most. Nasturtium is one of the few crops on this site with a pH band above the usual range, 6.0 to 7.0, while calendula wants 5.5 to 6.2. A tank held at 6.5 for nasturtium is too high for calendula, and one held at 5.8 is too low for nasturtium.
Light divides them too. Nasturtium runs 16 hours on and 8 off, because longer days give it more leaf and more flowers, whereas calendula runs the standard 14 hours. One light runs one schedule. So give each flower its own container and, ideally, its own timer. Nasturtium is happy sharing a 16 hour light with shiso or stevia, and calendula sits comfortably under the 14 hour light with your herbs. Shelf layouts for one light shows how to plan two schedules on one shelf.
Growing Hydroponic Nasturtiums
Nasturtium is the easier and more rewarding of the two. Everything above ground is edible, it flowers at a modest feed, and compact varieties stay small enough for a jar.
Choose a Compact Bush Type
Pick bush varieties such as Tom Thumb or Tip Top, which stay at about 6 to 12 inches. Trailing and climbing types spread a foot or more and outgrow a jar quickly; if you grow one, give it a trellis or a hanging spot. Space bush plants 8 to 12 inches apart.
Sowing
Nasturtium seed needs darkness to germinate, the opposite of many small seeds. Bury it about half an inch deep in a rockwool cube or plug soaked at pH 5.5, and keep it covered. It sprouts in 7 to 10 days. Once seedlings appear, put them under the light and feed at EC 0.8 to 1.0, one of the few crops on this site that starts below 1.0. Starting seeds in rockwool covers the method.
Jar or Bucket
Compact nasturtiums suit a Kratky container of about 1 gallon, with a 2 to 3 inch net cup. Fill it until the bottom of the cup sits in the solution, about half an inch to an inch deep, and let the level fall as the plant drinks, so an air gap forms by itself. Do not top it off every day, and never refill it to the brim. If it runs low, add a little nutrient solution, raising the level by no more than about an inch. For a longer run of flowers, a DWC setup of 1 to 2 gallons with an air stone works well; top off daily with plain pH-adjusted water and change the reservoir every 2 weeks. The Kratky jar setup guide covers the jar method.
Light, Feed and Temperature
Hold the pH at 6.0 to 7.0; nasturtium tolerates a very wide band and prefers the upper part of it. Feed established plants at EC 1.0 to 1.6. Give it 16 hours of light with the panel 6 to 8 inches above, at 300 PPFD or more. Nasturtium keeps gaining with more light, well past what most flowers need. Keep the room and water cool to moderate, at 55 to 75°F, since it does best with little heat stress. The grow light calculator checks whether your fixture reaches 300.
🌱 Plan this grow: The free Urban Hydro grow planner turns these numbers into a day-by-day care list for your nasturtium, with a harvest date and reminders; it covers calendula too. It runs in your browser, and an account is optional.
Growing Hydroponic Calendula
Calendula, sometimes called pot marigold, is a compact, bushy plant reaching 12 to 24 inches, with golden or orange flowers that keep coming for weeks or months if you keep picking them. It germinates reliably and flowers in modest conditions.
Sowing
Cover calendula seed, because light slows its germination. At about 70°F it sprouts in 7 to 14 days. Use a rockwool cube soaked at pH 5.5, and once seedlings are up, feed at EC 1.2 under the light. Space plants 8 to 12 inches apart.
Use an Aerated Container
Kratky is only marginal for calendula. The plant grows top-heavy and flowers over a long window, which strains a single fill. A DWC container of 1 to 2 gallons with an air stone and a 2 to 3 inch net cup suits it better. Top off daily with plain pH-adjusted water and change the reservoir every 2 weeks. The quiet air pump roundup helps keep the pump down, and DWC vs Kratky compares the systems.
Light, Feed and Air
Hold the pH at 5.5 to 6.2, aiming for 5.8 to 6.2, and feed at EC 1.2 to 1.8. Above about 1.8 to 2.0, calendula suffers salt stress and flowers less. Give it 14 hours of light with the panel 6 to 8 inches above. No calendula-specific light figure exists, but small flowering plants generally sit at 250 to 400 PPFD. Keep the water at 64 to 75°F.
Air matters more than anything else with calendula. Heat plus humidity rots its flower buds, so run a clip-on fan near the plants. When buds start to rot, bring humidity down toward 40 to 50 percent and increase the airflow around the blooms.
Getting Flowers, Not Just Leaves
With both flowers, the single biggest mistake is feeding them like leafy herbs. A nitrogen-heavy vegetative formula, or a high EC, pushes lush green growth and very few flowers. Nasturtium is especially prone to it; well-fed nasturtiums can become a big green mound with the odd bloom.
- Keep nasturtium at EC 1.0 to 1.6 and calendula at 1.2 to 1.8, rather than pushing either higher.
- Use a greens or flowering formula rather than a high-nitrogen growth formula once plants are established.
- Give them enough light: 16 hours for nasturtium and 14 for calendula, since too little light also means leaves without flowers.
- Pick flowers often. Removing spent blooms tells the plant to make more.
The pH and nutrient calculator works out doses, mixing two-part nutrients explains how to adjust a formula, and a reliable EC meter keeps you from creeping too high.
Harvesting and Eating Your Flowers
You can pick nasturtium leaves from about 4 weeks, and both plants give their first flowers at about 6 to 8 weeks from seed.
- Nasturtium flowers: cut at the base of the flower stem, while leaves are pinched off at the leaf stalk, near the crown.
- Nasturtium seeds: pick them while they are young and green, then pickle them as a caper substitute.
- Calendula: cut flower heads at the base of the stem when the petals open fully, several times a week.
Nasturtium tastes sharp and peppery, like mustard or cress, and every part is edible. Use flowers and leaves raw in salads and as a garnish. Calendula petals are slightly peppery and mildly bitter; pull them from the flower head and scatter them over salads and soups, or dry them for tea. Its leaves are edible but more bitter. Pick in the morning, rinse gently, and use them the same day, since flowers wilt fast. The seed to harvest calculator gives you a likely first-flower date.
What About Violas and Other Flowers?
Violas, pansies and signet marigolds are also grown as edible flowers, and many seed catalogs sell them for that. The crop table on this site does not yet document them for hydroponics, so this guide gives no figures for them. If you try one, start from a general herb setup and watch the plant closely, and buy seed sold as edible and untreated. Nasturtium and calendula are the dependable place to start.
Where these facts come from
🔗 Where these numbers come from
The pH, EC, light, temperature, container and timeline figures here are the ones the crop table on this site uses, and the crop sources page lists the research for nasturtium and calendula, including the long-day response of nasturtium. Johnny’s nasturtium growing information and the University of Wisconsin Extension article on calendula cover germination and care. The calendula light band is a general figure for small flowering plants, and light heights in inches are this site’s starting points.
Troubleshooting Edible Flowers
Most edible-flower problems are about feed, light, airflow or pests.
| What you see | Most likely cause | What to do |
|---|---|---|
| Lush leaves but few flowers | Too much nitrogen, or EC too high | Switch to a greens or flowering formula and also hold EC in the crop’s range |
| Sticky nasturtium leaves with small insects | Aphids, which favor nasturtium | Treat early with insecticidal soap and also improve airflow |
| Leggy, weak nasturtium stems | Light too weak, or days too short | Raise intensity to at least 300 PPFD and also keep 16 hours |
| Calendula buds rotting | High humidity and still air | Bring humidity toward 40 to 50 percent, then also add airflow |
| Pale calendula leaves and weak growth | Feed too weak | Raise the EC gradually until it reaches 1.2 to 1.5 |
| Brown, slimy roots | Warm, stagnant water | Cool and aerate the water before you treat the rot |
Aphids on Nasturtium
Aphids love nasturtium, and on a crop you eat whole that matters. Check the undersides of the leaves and the new growth weekly. Small numbers wash off at the sink; larger ones need insecticidal soap early, before they spread, and better airflow. Because you are eating the flowers, choose a treatment labeled safe for edible plants and follow its wait time. The aphid guide covers the full routine.
Root Rot
Healthy roots are white or cream. Brown, slimy roots with a pond smell mean the water has run too warm or stagnant. Trim the rot, refresh the solution, and in DWC make sure the air stone is running. For an active infection, add 3 ml of 3% hydrogen peroxide per liter, as hydrogen peroxide for root rot explains. Never cool a container with ice; a frozen bottle against the outside works better. Preventing root rot covers the rest.
One Last Tip
Pick the first flowers even when there are only two or three and it feels like a waste. A flower left to fade tells the plant its job is done, and it starts putting energy into seed instead of new buds. Picking early and often, even a single bloom for one salad, keeps both nasturtium and calendula flowering for far longer. The more you take, within reason, the more you get.
Frequently Asked Questions
Which edible flowers grow best hydroponically?
Nasturtium and calendula are the dependable choices. Both are rated Easy, flower about 6 to 8 weeks from seed, and grow well in water. Choose compact bush nasturtiums such as Tom Thumb or Tip Top. Violas and pansies are also eaten, but they are less documented for hydroponics.
Can nasturtium and calendula share a reservoir?
Not well. Nasturtium wants pH 6.0 to 7.0 and 16 hours of light, while calendula wants pH 5.5 to 6.2 and 14 hours. A tank suits one or the other, and one light runs one schedule. Grow them in separate containers, ideally under separate timers.
Why is my nasturtium all leaves and no flowers?
Usually too much nitrogen or too high an EC, which pushes leaf growth instead of flowers. Switch to a greens or flowering formula and hold the EC at 1.0 to 1.6. Make sure it gets 16 hours of light at 300 PPFD or more, and pick flowers often.
How much light do hydroponic edible flowers need?
Nasturtium runs 16 hours on and 8 off at 300 PPFD or more, and it keeps gaining with more light. Calendula runs the usual 14 hours on and 10 off, and small flowering plants generally do well at 250 to 400 PPFD. Keep the panel 6 to 8 inches above both.
How do I germinate nasturtium and calendula seeds?
Nasturtium seed needs darkness, so bury it about half an inch deep; it sprouts in 7 to 10 days. Calendula seed should be covered too, because light slows it, and it sprouts in 7 to 14 days at about 70°F. Start both in rockwool soaked at pH 5.5.
Can I grow edible flowers in a Kratky jar?
Compact nasturtiums, yes, in a container of about 1 gallon. Calendula is only marginal in Kratky, because it grows top-heavy and flowers over a long window, so an aerated container of 1 to 2 gallons suits it better. Never refill a Kratky jar to the brim.
Which parts of nasturtium can you eat?
All of it above ground. The flowers and leaves have a sharp, peppery taste like mustard or cress, the stems are edible, and young green seeds can be pickled as a caper substitute. Use flowers and leaves raw in salads or as a garnish.
How do you use calendula flowers?
Pull the petals from the flower head and scatter them over salads and soups, or dry them for tea. They taste slightly peppery and mildly bitter. The leaves are edible too, but more bitter. Cut flower heads as the petals open fully, several times a week.
Why are my calendula buds rotting?
High humidity with still air, especially in a warm room. Bring the humidity down toward 40 to 50 percent around the plants and add a small fan to move air past the blooms. Remove rotting buds straight away so the problem does not spread.
How often do I change the water for hydroponic flowers?
In an aerated container, top off daily with plain pH-adjusted water and change the reservoir every 2 weeks. In a Kratky jar, do not top off daily; let the level fall, and if it runs low, add a little nutrient solution, no more than about an inch.
