The Kratky method: passive hydroponics without a pump

The short version

Kratky growing suspends a plant above a static nutrient reservoir. As the level falls, an air gap forms and part of the root mass takes oxygen from it. The useful test is not whether a method can work, but whether it keeps the roots supplied with water, dissolved nutrients and oxygen while the leaves receive enough light.

• It is best for short, light crops such as lettuce and basil.
• An opaque container slows algae.
• Do not keep topping the liquid back to the crown.

A practical way to do it

1. 1

   Fill and mix the reservoir.

   Make this change deliberately, then observe the plant and system before changing the next variable. That separation makes the result useful.

2. 2

   Support a rooted plug just above the solution.

   Make this change deliberately, then observe the plant and system before changing the next variable. That separation makes the result useful.

3. 3

   Cover every gap around the net pot.

   Make this change deliberately, then observe the plant and system before changing the next variable. That separation makes the result useful.

4. 4

   Let the level fall while watching root health.

   Make this change deliberately, then observe the plant and system before changing the next variable. That separation makes the result useful.

What to watch

Look at the whole system before diagnosing a single leaf. Check new and old growth separately, lift the lid to inspect root colour and texture, confirm that water or air is moving, and compare today’s readings with the last entry in your log.

Make the setup easier to live with

Put inspection points where you can reach them without moving plants. Label cables, nutrient bottles and measuring tools. A waterproof tray, a marked full-water line and a simple notebook prevent more trouble than an elaborate controller. When a crop finishes, remove roots promptly and clean the parts you can now reach.

Questions people ask