No pumps. No electricity. No daily maintenance. The Kratky method is the easiest possible introduction to hydroponics — and it's perfect for growing lettuce on your windowsill.
What is the Kratky method?
Invented by Dr. Bernard Kratky at the University of Hawaii, it's passive hydroponics: you suspend a plant above a reservoir of nutrient water. As the plant drinks, the water level drops, and the exposed roots breathe the oxygen in the growing air gap. No pump required, ever.
What you need
- A mason jar or food-grade bucket (1 quart for lettuce, 5 gallons for bigger plants).
- A 2-inch net pot that fits the lid.
- Hydroton (clay pebbles) or rockwool.
- General Hydroponics MaxiGro or Flora Series nutrients.
- A pH testing kit.
- Seeds (lettuce and basil are easiest).
Step-by-step setup
- Germinate seeds in rockwool until roots poke out.
- Mix nutrient solution per the bottle's instructions; adjust pH to 5.8–6.2.
- Fill the jar so the bottom of the net pot just touches the water.
- Place the seedling in the net pot, surrounded by hydroton.
- Put it in a bright window or under a grow light.
- Don't refill. As water drops, more roots become air roots — exactly what we want.
Best plants for Kratky
- Easiest: Lettuce, basil, mint, parsley, cilantro.
- Possible: Spinach, kale, Swiss chard (use bigger reservoirs).
- Skip: Tomatoes, peppers — they drink too much.
Frequently asked questions
Do I need to add air?
No. That's the magic of Kratky — the air gap above the falling waterline replaces the air pump.
Will the water go bad?
If you keep light out of the reservoir (wrap it in foil or use an opaque container), algae won't grow and the solution stays good for a full grow cycle.
What if I run out of water before harvest?
Top up with plain pH-adjusted water, not more nutrient solution — concentrations get too high otherwise.
Comments (0)
Join the conversation. Be kind — offensive language is automatically filtered.
Loading…
Loading comments...
Keep reading
Plant Guides
How to Grow Lettuce Hydroponically (28-Day Guide)
Crisp, sweet butterhead lettuce in 28 days using the Kratky method. No pumps required.
Beginner
Hydroponics for Beginners: A Complete Starter Guide
What hydroponics is, the 6 main types, and exactly which one to pick if you've never grown a plant.
Beginner
Deep Water Culture vs NFT: Which Should You Build?
DWC vs NFT — how each works, what they grow best, and which to start with.