The Kratky Method

Named after Dr. B. A. Kratky from the University of Hawaii, this method requires minimal work, and provides excellent results in leafy plants with fast grow times, as well as being able to sustain larger crops in commercial farming applications. In comparison to other hydroponic methods, it has very few requirements for equipment, and can use no electricity if you grow outside. Because of this, Kratky makes a great way to get into indoor gardening with minimal effort.

How it works

Dr Kratky explains this process pretty well in the opening 3 minutes of his  presentation:

The short version is that you pre-mix the nutrient solution for the life of the plant, place the plant roots in the solution, and let it grow. As the water gets used up, it leaves behind a moist air space that the plant uses to get air. This solution can either be placed directly below the plants, or fed via float valve or any other way to maintain a uniform nutrient depth.

There are no pumps, electronics, or aeration. Because of this, you should keep things clean and prevent bacterial contamination. This is one of the best ways to get started in hydroponics.

Why should you grow this way?

It’s easy and doesn’t require a lot of effort. You don’t need expensive equipment. Anyone can do this to get a bounty of herbs, tomatoes, cucumbers, etc.

Why should you not grow this way?

I don’t normally put in a “Why shouldn’t you do this” section in our method documentation, and I’m doing it here because if you look at online forums enough, you are never surprised when someone says “Kratky” and “help” in the same sentence. Unfortunately, these systems get root diseases easily, and nutrient imbalances run rampant.

Because the aeration is dependent on the root system making special fibers, and not just absorbing it through regular roots, plants grown this way take longer to develop than in traditional hydro, although still faster than soil in most cases.

replacing the nutrient solution and cleaning out the root area soles many of these issues if you catch them early enough. Adding the occasional hit of hydrogen peroxide (no more than 3ml/gal) helps immensely as well. Mostly, having everything ready to go all at once, and ensuring that you aren’t taking shortcuts, greatly increase your chance that you’ll have a better grow.

What you need to get started

You need a seedling, a container, something to hold the plant, and fertilizer.

Gather your initial materials:

• A seedling
• A container large enough to hold enough nutrient solution to grow your plant.
  • For herbs, a wide-mouth, 1 quart, mason jar, a 3-inch net cup
  • For lettuce, spinach, etc, use a gallon water jug, and a 1 inch net cup
• A rockwool cube or peat pellets
• Your favorite fertilizer (MaxiGrow is your best bang for the buck, but you will need to pH it back up over 5.5)

Refer to our seedling guide if you need help getting that going. Once you have one with a few roots, get ready to transplant:

• Mix the fertilizer and put it in the container. If you are using a powdered fertilizer, don’t bother mixing it up; it will dissolve in a few days and that will help the plant acclimate to the solution.
• Put your seedling in the net cup and put that in the nutrient solution.
• Put it in some light.
• Wait.
• Eat.

That too small? Make up a batch in a 10 gallon tote and grow 10 heads of lettuce. Grab a 27-gallon tote and grow a massive tomato plant. Build a table tray and feed it with a float valve to grow 50 plants. Want to watch a grown man grow a Japanese cucumber plant in a corner using only a 27 gallon tote, a quick trip to Home Depot, and fertilizer? Of course you do.

Kratky Tips

Keep the following in mind to get the best out of this:

• Keep the nutrient solution in the dark.
• Mix the nutrient solution for the life of the plant at the beginning of the process, or prepare to do a bunch of EC testing when topping off with water and more nutrients.
• On that note, avoid topping off with water too much. Once every couple of weeks is fine, but too much messes up the ratios of nutrients.
• Sanitize your initial system to some degree. It can be as simple as filling it with chlorinated tap water for a bit. If you get scum in the container form a previous grow, scrub it out and sanitize it fully.