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Lettuce is the classic first hydroponic crop: a mason-jar Kratky setup or countertop unit takes it from seed to salad in 30-45 days with no pumps or daily attention. Keep the nutrient solution at pH 5.5-6.0 and EC 0.8-1.2, keep the reservoir cool (under 22°C), and use net pots in an opaque container. The two failures you'll actually meet are root rot in warm reservoirs and tip burn on inner leaves from calcium transport, not pests.
Key facts
- Kratky method — a lidded opaque jar, net pot, and nutrient solution, no pump or electricity — grows a full lettuce head as the water level drops and air roots form in the gap.
- Targets: pH 5.5-6.0, EC 0.8-1.2 mS/cm (roughly 560-840 ppm on the 700 scale). Lettuce burns easily on strong solution.
- Under a basic grow light, loose-leaf varieties are cut-and-come-again from day 30; heading types take 45-60 days.
- For soil/garden growing of the same plant, see /plants/outdoor/lettuce — this page covers only hydroponics.
Care requirements#
| Growing method | Kratky jars (passive), DWC bucket with air stone, or countertop units (AeroGarden-style) |
| System for beginners | Kratky: 1L+ opaque jar, 5cm net pot, rockwool or sponge plug — zero moving parts |
| Nutrient solution | Any balanced hydroponic formula (e.g. lettuce/leafy-green blend) at EC 0.8-1.2 mS/cm / ~560-840 ppm |
| Solution pH | 5.5-6.0; check weekly with drops or a pen and adjust with pH down (usually needed) or up |
| Reservoir temperature | 18-22°C ideal; above 24°C dissolved oxygen drops and root rot (Pythium) takes hold |
| Light | 14-16 hours under a small full-spectrum LED, or a very bright windowsill (slower, leggier) |
| Reservoir management | Kratky: set and leave until harvest for one head. DWC: top up with half-strength solution, full change every 2-3 weeks |
| Algae control | Opaque containers only, or wrap clear jars in foil/tape; light + nutrients = green slime |
| Air gap (Kratky) | As the level drops, upper roots become air roots — never refill to the stem or they drown |
| Spacing | One head per jar; 15-20cm between net pots in shared reservoirs |
| Temperature (air) | 15-21°C keeps lettuce sweet; heat triggers bolting and bitterness |
| Harvest | Cut outer leaves from day 30, or take the whole head at 45-60 days |
Growth & propagation#
| Days to harvest | Loose-leaf 30-45 days; butterhead/romaine 45-60 days under lights |
| Germination | 2-4 days in a moist rockwool cube or sponge; transplant to the system at 2 true leaves |
| Growth vs soil | Comparable or faster than soil under good light — lettuce is hydroponics' showcase crop |
| Succession | Start a new plug every week for a continuous salad supply |
| Regrowth | Cut-and-come-again works 2-3 times before leaves turn bitter |
| Lifespan | One crop cycle; hydro lettuce is replanted, not maintained |
Common problems & troubleshooting#
| Symptom | Likely cause | Fix |
|---|---|---|
| Brown, slimy roots and stalled growth | Root rot (Pythium) in a warm, oxygen-poor reservoir | Cool the reservoir below 22°C, add an air stone (DWC), change solution, and shade the container from heat |
| Brown, dead edges on young inner leaves | Tip burn — a calcium transport problem from fast growth and low airflow, not usually a calcium shortage in the solution | Add a small fan for airflow, reduce light intensity/hours slightly, and keep EC at the low end |
| Green slime in the reservoir | Algae — light reaching the nutrient solution | Use opaque containers or wrap clear ones completely; clean and restart if established |
| Plant suddenly sends up a tall stalk and turns bitter | Bolting from heat or long hot days | Harvest immediately; keep air under 24°C and choose slow-bolt varieties next round |
| Pale yellowing leaves across the plant | Solution too weak or exhausted | Re-dose to EC 0.8-1.2; in Kratky jars this usually means the head is ready to harvest anyway |
Reservoir checks, on schedule
Sodate reminds you when to top up, re-dose, and check pH so a jar never runs dry mid-head.
Seasonal care#
Varieties & cultivars#
| Variety | Distinguishing trait | Note |
|---|---|---|
| 'Salanova' / one-cut types | Dense rosettes bred for hydroponics | The commercial greenhouse standard |
| 'Buttercrunch' (butterhead) | Soft, sweet folding heads | Reliable classic in Kratky jars |
| 'Black Seeded Simpson' (loose-leaf) | Fast, frilly light-green leaves | Quickest cut-and-come-again option |
| 'Rex' (butterhead) | Bolt- and tip-burn-resistant | Bred specifically for hydroponic production |
Buying checklist#
- A starter kit needs: opaque container, net pots, rockwool or sponge plugs, hydroponic nutrient (two-part or leafy-green blend), and pH test drops
- Pelleted lettuce seed is easier to handle in plugs than raw seed
- A cheap EC/TDS pen ($10-15) pays for itself in avoided guesswork
- Skip clear containers unless you enjoy fighting algae
Pricing by region#
| Region | Price range | Typical unit | Basis |
|---|---|---|---|
| US | $25 – $60 | Kratky/DWC starter kit + seeds + nutrient | DIY jar setup at the low end; small LED + kit at the high; countertop units run $80-200 |
| UK | $25 – $57 | starter kit + seeds + nutrient | Hydro shop or online kit |
| India | $12 – $36 | starter kit + seeds + nutrient | Local hydroponic kit suppliers; DIY far cheaper |
| Australia | $26 – $65 | starter kit + seeds + nutrient | Hydro retail is well established |
| Canada | $26 – $63 | starter kit + seeds + nutrient | Hydro shop/online kit |
USD figures are approximate conversions for comparison; switch the dropdown to see each region's actual local-currency listing price.
Often confused with#
Name confusion warning#
Method page. This covers lettuce grown hydroponically at home. For garden-bed and container soil growing of the same crop, see our lettuce page.
Where it's actually grown#
Hydroponic lettuce is now a major commercial category — most 'living lettuce' sold with roots attached in supermarkets comes from greenhouse NFT or pond systems in the Netherlands, Ontario, Australia, and US CEA farms. Home growers buy ordinary seed; no special 'hydroponic seed' exists.
Import & biosecurity restrictions#
| Region | Note |
|---|---|
| Australia | Lettuce seed imports are permitted with declarations; live seedlings restricted under biosecurity law. Domestic seed is everywhere. |
| US | No restriction on seed or home hydro equipment. |
| UK | No restriction; seed freely sold. |
| India | No restriction; hydroponics is a growing urban-farming sector. |
| Canada | No restriction on seed; hydro equipment widely sold. |
Similar plants
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Frequently asked questions
How long does hydroponic lettuce take to grow?
Loose-leaf types give first cuttings in about 30-45 days from seed under lights; full heads of butterhead or romaine take 45-60 days.
What pH and EC does hydroponic lettuce need?
pH 5.5-6.0 and EC 0.8-1.2 mS/cm (roughly 560-840 ppm) — lettuce prefers a weaker solution than most crops.
Do I need a pump to grow lettuce hydroponically?
No — the Kratky method grows a full head in a lidded opaque jar with no pump or electricity; you only need a light if your windowsill is dim.
Why are the inner leaf edges turning brown?
That's tip burn, a calcium transport issue from fast growth and still air — add a small fan, ease off the light, and keep the solution at the weak end.
What does a starter setup cost?
About $25-60 for a DIY Kratky or small DWC kit with nutrient and seeds; sealed countertop units run $80-200.