The Kratky Method: How To Grow Food Almost Automatically

Although I already think that hydroponics is one of the most interesting, simple, and productive gardening methods out there, what continues to surprise me is the amount of innovation that happens in the field. There are so many different hydroponic systems out there and they seem to be limited only by our imagination.

Not too long ago I was looking for more ways to experiment with my deep water culture systems, including building a very simple hydroponics for kids project. I wanted to keep the system as simple as possible while making sure it still produced a healthy plant.

Enter the Kratky Method.​

What Is The Kratky Method?

Let's start off with my video overview of the Kratky Method:

Because hydroponics grows plants without soil, there are often a lot of moving parts in a hydroponic system: pumps, wicks, airstones…and the electricity to power them all. Don’t get me wrong – this is part of what I LOVE about hydroponics – but sometimes you just want to keep it simple.

This is where the Kratky method shines. It’s a technique that allows you to grow hydroponically without electricity, pumps, or wicks of any kind. In fact, you don’t even have to change your reservoir or add nutrients. It’s as close to a completely “hands off” growing technique as I’ve ever seen.

How to Build a Kratky System

This is a really fun method to mess around with – give it a shot! Once you understand the basic principles, it’s probably the easiest and cheapest method you could ever use to grow hydroponically.

Here's everything you need to get started with the Kratky method:

Part List

 Details

Link

5 Gallon Bucket

3" Net Pots

3" Hole Bit

Growing Media

Nutrients

ph Control Kit

PPM Meter

How The Kratky Method Works In Detail

In a traditional deep water culture setup, you typically have your plant in a net pot with growing medium and you place it in a reservoir. Then you fill the reservoir with nutrient solution up to a certain point, making sure it doesn’t touch the net pot.

The airstone that you add to your system will create bubbles that pop at the surface of the water, hitting your growing media and feeding your plant’s young root system. As the roots grow, they’ll eventually hit the surface of the water and growth will explode from there on out.

With the Kratky Method, you actually fill your reservoir with properly conditioned water further, making sure to cover the bottom third of the net pot with water. The reason? Without an airstone, your plants will need water at the start of their lives, and this technique ensures they’ll never dry out as your growing media is constantly wet.

As the plant continues to grow, it will use water and the water level will decline – but your plant’s roots will have descended into the nutrient solution by that time.

You might be wondering, “Aren’t airstones used for more than just wetting the growing media in the seedling phase?” You’re right – this is where the beauty of the Kratky Method starts to shine. Because you are not refilling your reservoir, your plants will keep using up water and exposing more and more of their root systems to the air, which will ensure your plants get enough oxygen to survive and thrive.

Potential Problems With The Kratky Method

Like any system, there are some flaws and considerations you should be aware of if you want to make sure you have a successful grow.

Good for Leafy Greens Only - This is designed to be a simple, hands-off method. That means it can’t really account for the increased nutrient and water requirements of plants that bear fruit. Use this for leafy greens like lettuce, spinach, etc – not fruiting plants like tomatoes, cucumbers, etc.

Pests – Because your nutrient solution will be still (because you’re not using an airstone), it can draw the attention of pests, namely mosquitoes. To avoid this, make sure that the reservoir is protected from any type of bug or pest, while allowing some oxygen and air to flow in as well.

Water Quality – You are not going to be replacing or adjusting the water level in your reservoir, so it’s important to start with very high quality water. If you’re going with the Kratky Method, I would recommend reverse osmosis or filtered water – get your PPM as low as possible so you avoid a dangerous concentration of salts.

Watch Your pH – If you’re new to the method, you may want to pick up a pH pen and test it every day. Once you get the hang of how to prepare your nutrient reservoir for the plant that you’re growing, you can leave the system to do its job!


*You can find the original paper about the Kratky method here. Be forewarned, it gets a little technical!

See also:
  • I’m curious about time-to-harvest with the Kratky method vs. DWC or even perhaps an NFT system. Is it going to be substantially slower?

    • epicgardening

      In theory they should be about the same – I would only guess that a Kratky may slow down because of lower oxygenation in the water or potentially miscalculated water / nutrient needs. I haven’t done a full side by side grow though, so I can’t say for sure @dylangordon:disqus

    • JEFF

      I have used it and when following all the rules. Grow time is reduced , plants are very healthy. but if you do not use the right type fertilizer and start with air stones and check PH bi-weekly. it will fail. calcium nitrate for the green as the additional nitrogen or it will go acid and fail; learned By experience.

      • Thanks for sharing Jeff – this is what I’ve noticed as well. Kratky still takes some effort, definitely not completely hands off!

    • John C

      it’s only slightly better than dirt…

  • Katiedee

    I tried this method with using rock wool in the net pots. I planted herb seeds in the rock wool and they did sprout, however, they all reached a certain point and then died off. The rock wool stayed wet, so I filled the container just to the bottom of the net cup without touching the rock wool. I hung these cups in a large tray beneath my skylight. I eventually removed all the herb cups and replaced with ivy, which is doing very well. Maybe starting with seedlings is better, but any suggestions on how to grow herbs using the Kratky method and rock wool?

    • Istenbaszott

      Did you soak your rock wool in PH-ed water? I never used rock wool for sprouting but as far as I know you have to soak them for a day in PH-ed water otherwise it will mess up the PH of your res.

      • Katiedee

        No, I didn’t soak them. They all sprouted and grew about an inch, but then just died off. I just assumed it was because the rock wool stayed too wet. There seems to be a fine line between the right amount of moisture and too much.

        • Istenbaszott

          I see, I would assume you are right about this while its sprouting. Maybe you could try clay pebbles. They wont get as wet. I didnt had a chance to try this out yet unfortunately so sorry for trying to help blind folded. I just use normal ebb&flow system.

          • How’s the ebb and flow working out for you?

          • Istenbaszott

            I can tell you two cons:
            -Clay pebbles what I use mess up always after cleaning the PH of my reservoir, takes 2 weeks to stabilise it.
            -If you want to change plants you have to clean everything, Now if you have even a small table with about 60-80 Litres of clay pebbles ,that takes a lot of time.

            Except these two everything else is a perfect ,and these are also only problems if you are veeeery lazy.

            Currently im thinking about changing/trying DWC, but I don’t really expect it to be any easier but its worth a try.

            Another thing im looking forward is to try this Kratky Method ,but I still don’t know what kind of nuts i should use. Im from EU ,and its a bit harder here to find the correct one.

    • A common issue with rockwool is that it will retain water a bit too well and drown out your roots or cause root rot. That may be the issue you ran into!

  • Adriaan Bester

    Im thinking of using Vermicompost tea with the Kratky method for my Herbs.Instead of liquid fertilizer.

    Adding 10% of my water volume in Vermicompost tea weekly.
    Anybody ever done it?
    What do you guys think?

    • Haven’t done it, but very interested to see how it works for you!

  • Interesting method on growing plants. Thanks for sharing.

  • Derhel

    I’ve been trying to use this method to grow lettuce, but instead of starting with seeds i used seedlings, My question is , do I have to leave a gap between the net pot and the nutrient solution for oxygenation purposes or can fill the container until it touches the net pot? I noticed that lettuces somehow are losing color and I think it might be related to lack of oxygen.
    Thanks in advance

    • Yes, leave a gap so some portion of the roots are always exposed to air…otherwise you run the risk of drowning your plant.

  • I was thinking maybe I should add this to my blog, but most of my readers did not like this. Maybe they are old-fashioned gardeners.