The Kratky method (sometimes referred to as passive hydroponics or jar hydroponics) is the easiest form of hydroponic growing because it doesn’t require any water pumps, air pumps, and can be done in a simple mason jar. The roots begin submerged in the nutrient solution, but are slowly exposed to more air as they grow down lower into the jar and the solution evaporates. There’s no need to change out the water, nor is there a concern about rejuvenating oxygen for the plants.
As the plant grows, the water level drops, creating air space for the roots. When the plant is ready for harvest, the nutrient-filled water is nearly used up. If the jar size is calculated correctly, the water does not need replenishing and you can fill the jar only once.
After the plant is harvested, the gardener can refill the tank and place new transplants on top of the tank to start another crop. After three to five growing cycles, the jar should be cleaned.
