Kratky Method

October 13, 2022

By Jeff Hale

If you’ve been browsing the hydroponic internet, you might have seen the term Kratky method mentioned. But what does it entail?

Comparing it to other hydroponic techniques, this is the most basic and easy to accomplish.

It was developed by a researcher named Bernard Kratky at the University of Hawaii in the 1990s. So, in terms of developments in the 20th century, it is younger than the invention of the internet – which has a birthday of January 1, 1983.

But what makes this method so revolutionary in the horticultural space?

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Related: Types of Hydroponic Systems

Why Is The Kratky Method So Revolutionary?

Simply put, it is a totally passive method of hydroponics. It does not require an air or water pump. The plant’s roots are simply suspended in the nutrient solution with enough air between the top of the water and the base of the plant to supply it’s needs.

This technique lends itself to a basic introduction to aquaponics, which requires fish and a water reservoir. Aquaponics differs from hydroponics as it is a balancing act between fish and plants. The fish’s defecation feeds the plants a rich nitrogen source, and the plants nourish the fish.

The Kratky method is perfect for those who are currently homesteading and don’t have access to the same utilities as average suburban homes like endless supplies of water and electricity.

While these homesteaders would be considered more experienced, the other target demographic is novices and children.

For novices, it is easy to test pH and clean the reservoir, and for children, they can see firsthand how plants put their roots down.

While most will associate the Kratky method with a smaller countertop setup, like sticking a basil cutting in a glass of water, you can scale it up. You can make what could be considered a raft technique, but the main difference is that the Kratky method requires that the plant is held above the water line, with only the roots touching the nutrient solution.

What You’ll Need To Get Started With The Kratky Method

As we mentioned, this method does not require an air or water pump, making this the most accessible method of hydroponics. If you are only interested in testing the hydroponic waters, this is it.

What you’ll need to get started is:

A container or reservoir
Some sort of lid to cover the water with a hole in the middle
A single net pot to fit into the lid
Growing media
Hydroponic nutrients
A pH meter
A pH up and down solution

While you can purchase a complete Kratky Method kit online, honestly, it is simple enough to make one yourself with simple tools at home.

Here’s the basic run down.

Make a Hole In the Lid of Your Container

Before cutting a hole in a perfectly good lid, ensure the plant you’re growing will be well suited to the method.

Generally, you want to grow a leafy plant that won’t require a larger space for its roots. So, no lemon or orange trees.

The list of appropriate plants includes:

Lettuces
Spinaches
Herbs
Beans
And cherry tomatoes

In our opinion, the right-sized Kratky method container could yield an excellent spinach crop.

Once you’re happy with your crop selection, you can cut the hole to fit the net pot inside.

Potting the Plants

For this method to work, you must adequately pot your plants into your potting medium. We’d suggest using lightweight expanded clay aggregate (LECA) as your medium. It’s light and easy to place around the roots of the plant.

LECA also retains water nicely, as well as giving ample support to the plant and roots.

When placing the plant into the pot, make sure the roots are at the bottom of the net pot. This will ensure that the plant’s roots chase the reservoir’s top water level.

The next step is filling the reservoir.

Fill The Reservoir

Once you’re happy with the potting of the plant, it’s time to fill the container. Ensure the water level is a little above the bottom of the net pot once the lid is in place.

You want to ensure that the roots can drink the solution and keep up with the water level. The water you use can be from the tap, but if your drinking water has heavy metals or other contaminants, you might want to use distilled water.

The next step is to add the hydroponic nutrients to the reservoir. Make sure to follow the instructions on the label and stir well.

Always check the pH levels before placing the plant into the solution. A normal reading will be between 5.5 – 6.5, but be aware that certain plants will like pHs of different levels.

If the nutrient solution needs adjustments, you can use the pH kit to fix the issue.

Once this is done, you’re ready to put the pot into place.

But how does the Kratky Method work?

How Does The Kratky Method Work?

For those who have been gardening using hydroponics, it will be a surprise that the plants don’t simply suffocate or experience some sort of root rot.

But the plant does all the work to ensure that this doesn’t happen. The container, as stated needs to have the roots semi-submerged in the nutrient solution.

This allows the roots’ top part to be exposed to the air. This means that the plant can access enough water and air to fulfill its needs simultaneously. Also, the plant gets all the necessary nutrients by absorbing water.

As the plant’s roots improve and grow, the water level gets lower.

By the time the plant is ready to be harvested, the water should be nearly completely absorbed, and the process can start over again.

Getting the balance will take practice, but when you’ve found that perfect equilibrium, it should be as easy as planting it and forgetting about it until it is ready to harvest.

While this is the easiest method of hydroponics, there are some downsides.

Some Downsides

There is no hydroponic method that is without flaws. For the Kratky Method, there are three concerns, mainly:

Pests

While the passive system means it is quiet, the fact is the water is static. This is a perfect breeding ground for mosquitoes and other water-born pests.

Ensure the lid fits tightly to ensure they can’t access the reservoir. And if there are pests, replace the nutrient solution.

Small Plants Only

This system won’t scale up for larger plants as they require more water and nutrients, and that means adding aeration in the system.

Balancing Act

Many sources on the internet will say this is a hands-off approach but that isn’t the case; the Kratky Method requires constant tweaking and adjustments to get it right.

You will also need to monitor the pH levels as smaller environments are prone to drastic pH changes.

Other than these issues, you will be ready to go.