Kratky Method Complete Guide

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The Kratky method is hydroponics stripped to its essentials. No pumps. No electricity. Just plants growing in nutrient water. It's named after B.A. Kratky, the researcher who formalised the technique.

How It Works: Fill a container with nutrient solution. Suspend a plant so roots reach the water. Leave an air gap between the water surface and the net pot.

As the plant drinks, the water level drops. Roots that were submerged become exposed to air, providing oxygen. New roots grow downward to follow the water. The plant regulates itself.

The Air Gap Is Everything: Roots need oxygen. Fully submerged roots will rot. The air gap lets upper roots breathe while lower roots drink. Don't top up the water and eliminate this gap.

Container Selection:

Mason jars: Perfect for single herbs. Wrap in foil or paint to block light (prevents algae).

Storage boxes: Good for multiple plants. Opaque is ideal.

5-litre buckets: Excellent for larger plants like tomatoes (though these push the method's limits).

Depth matters. Deeper containers hold more solution, which means less frequent monitoring.

Setting Up:

1. Fill container with nutrient solution at half strength 2. Place net pot with growing medium (clay pebbles or rockwool) 3. Add seedling with roots touching water 4. Position so 2-3cm air gap exists below net pot 5. Place under light or in sunny window 6. Walk away

Best Kratky Crops:

Excellent: Lettuce, herbs (basil, mint, coriander), spinach, pak choi, rocket.

Possible: Tomatoes, peppers (need large containers, more nutrients, strong light).

Difficult: Root vegetables, anything requiring support structures.

Common Mistakes:

Topping up water: This eliminates the air gap. Only add water if the container is nearly empty and the plant is large enough to handle brief submersion.

Too much light on solution: Causes algae. Use opaque containers or wrap in foil.

Too strong nutrients: Start at 50% strength for seedlings.

The Limitations: Kratky works best for single-harvest or cut-and-come-again crops. Long-term plants eventually exhaust nutrients and may need intervention. It's not truly "set and forget" for everything.

Our Take: Kratky is the best way to learn hydroponics. Success builds confidence. Start with lettuce in a mason jar. If it works, scale up. If it fails, you've learned something for under £5 in materials.

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