Exploring the Kratky Hydroponic Method: Simple, Sustainable, and Productive

Two winters ago, a sweet customer came in with some questions regarding indoor hydroponic gardening.  I was happy to give her my tips & tricks. Towards the end of the conversation, she asked me about something I had not heard of: The Kratky Method. She gave me a basic explanation of what the Kratky Method was and how to set up a basic system.  I immediately had my doubts until she showed me photos of her thriving Kratky garden.  From that point on, I knew I had to learn more and try it myself.  

What is the Kratky Method?

The Kratky hydroponic method is a passive hydroponic system developed by Dr. Bernard A. Kratky. This method is particularly well-suited for growing leafy greens and certain herbs. It is known for its minimalistic approach, requiring little equipment, making it an excellent choice for beginners and those who prefer a low-tech, cost-effective approach to hydroponics.

Here’s how the Kratky hydroponic method works:

  • Reservoir: You start with a container, which could be a large reservoir, a bucket or even a mason jar. This container holds the nutrient solution, which provides essential “food” to the plants.  It’s best to have a dark reservoir. If you’re choosing to use something like a glass mason jar, you will want to darken the glass. This could be by sewing a sleeve for it, putting duct tape around it, spray painting it or any other method to darken the glass.
  • Net Cup: The net cup will go into the reservoir, usually held up by some sort of lid or lip on the reservoir.  The net cup will hold the growing media, whether it’s rockwool, leca, perlite or coconut coir.
  • Planting: Plant your seedlings in the growing media you have chosen. In my experience, it has been easiest to start seeds in rockwool.
  • Nutrient Solution: Fill the reservoir with a weak nutrient solution, which is a water-based solution containing all the essential nutrients required for plant growth. As the seedling grows, the roots of the plants absorb these nutrients from the solution.  When  your seedlings get larger, you will need to increase the concentration of the nutrient solution.  My favorite nutrients to use are FloraMax’s Veg-1 or FoxFarm’s Grow Big Hydro.
  • Light: Position your Kratky setup in an area with appropriate lighting for the specific plants you are growing. If you are using your Kratky system inside the house (which is very common) you will need grow lights. Read more about selecting a grow light here.
  • pH Monitoring:  pH refers to the acidity or alkalinity of the nutrient solution and is crucial in all hydroponic systems–not just the Kratky System.  Without getting into too much chemistry, the pH of your hydroponic system should be somewhere between 5.5-6.5.  The starting pH of your water and your liquid nutrients will affect the pH of your system. pH can be measured by a simple test kit (I like General Hydroponics pH test kit for around $8) or it can be measured with a digital pH meter (these will range from $40-$200+).  

The key feature of the Kratky method is that it relies on the initial, static nutrient solution level to sustain the plants as they grow. As the plants consume water and nutrients, the solution level in the container decreases, exposing more of the roots to oxygen as they grow longer. This interaction between the roots, nutrient solution, and air allows the plants to thrive without the need for additional equipment like pumps or aerators.  As the plant drinks the nutrient rich water, the gardener must refill so that the plant does not completely dry out.  Simple. 

Thinking about starting your own Kratky hydroponic system? Stop by 111 S Broadway in Belgrade, MT for all of the supplies you will need!

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