The Practical Guide to the Kratky Method – Part 1: Introduction

Do you want to grow lots of lettuce, but are constantly hampered by the fact that it’s either too hot or too cold? How about the fact that lettuce is just about the favorite garden plant for bugs to eat? Or – do you want to try your hand at hydroponics, but don’t want to spend a fortune on tubs, pumps, filters and other supplies? Utilizing the Kratky method of hydroponic farming is a great solution to all of these problems. In this series of articles, I’ll walk you through the ins and outs of putting together your own Kratky lettuce farming rig. To start with, I’d like to introduce you to what the Kratky method is, how it works, and what you’ll need to get started.

History of the Kratky method

Bernard Kratky is a researcher in Hawaii who was attempting to devise an extremely water-efficient way to grow crops in areas that don’t have access to electricity. He found considerable success with with a specific method of hydroponics, which is termed the “Kratky method”. In his paper, “non-circulating hydroponic systems for vegetable production”, Bernard Kratky first documents his findings on how crops can be grown in simple tubs of water. He finds that plants grown this way will organize their root systems such that the upper roots absorb oxygen while the lower roots absorb water and nutrients.

I highly recommend anyone interested in the science behind this concept to check his paper out. It can be found by clicking here.

Basics of the Kratky method

At its core, the Kratky method is a way to grow plants hydroponically without having to use electrical pumps to mix, aerate and filter the water and nutrients that the plants are growing in. Unlike most hydroponic set-ups, Kratky rigs are often designed to work outdoors, where the plants can grow using natural sunlight. Many people have configured Kratky growing areas that resemble natural gardens with great success! Of course, indoor growing using grow lights is also an option.

Pictured are the roots of a middle-aged lettuce in a Kratky growing apparatus. The upper roots specialize in collecting oxygen while the lower roots suck up the nutrient solution. Note: lifting the lid of a Kratky set-up is not recommended.

While the materials and maintenance of a Kratky growing operation are very simple, you must adhere to a very specific set of rules and set-up guidelines if you want to have success. This is the reason why this very simple method of growing has not really caught on until the last 10 years. We will go over these procedures in a later article.

What can you grow with the Kratky method?

The Kratky method was originally developed with the intent to grow short-lived, non-fruiting plants like lettuce and herbs. It really excels with these types of plants. In most cases, growing them will be a “set it and forget it” situation – no need to ever refill the water or do anything really until you harvest the plant.

What about fruiting plants? Bernard Kratky himself reported success in growing tomatoes and cucumbers in his original research paper (linked above). Yields will be slightly lower, and you need to take extra precautions with regards to supporting the plants and refilling the nutrient solution. We will address these extra precautions in part 3 of this series.

The Kratky method is not an ideal way to grow root vegetables like potatoes, onions, radishes or similar. We have seen some folks have some success with this, but in almost all cases it seems like it would be much easier to simply put these types of plants in the ground.

We like one YouTube channel in particular that focuses on growing plants using the Kratky Method: Jeb Gardener. He has several videos posted where he grows everything from cilantro to tomatoes to radishes. If you’re thinking about giving the Kratky method a try – check out his channel for some inspiration!

What materials will you need for Kratky farming?

A Kratky growing rig is generally an extremely simple set-up consisting of an opaque container, some liquid and an apparatus for holding a plant growing in rockwool or a similar growing medium. In the tables below, we will list out materials you will need along with their costs if you had bought them on Amazon – but keep in mind that many of these materials are flexible! For example, you do not need to buy the container we link – you can use pretty much any container that will hold an appreciable amount of water. Similarly, you do not need to paint containers that are already opaque.

Item Link
An opaque storage container with a lid
Net cups for holding the growing medium but allowing root growth
A rack or shelf to get your container off of the ground
Total:

You’ll also need some tools to build the rig and get your seeds started:

All told, you can easily purchase the materials needed for your first grow for under $100. That may seem steep, but these materials will then last you through hundreds (or thousands!) of plants. As mentioned above – those on a budget can most likely use items that can be found around the home to replace most of the items found above. Get creative!

How Much do Plants Grown With the Kratky Method Cost?

Extending on the previous section, your per-plant cost will be dependent on the consumable materials you use for each plant you grow. Unlike the items in the previous section, you need to be careful when buying materials for plant growth. Home depot fertilizer will not work here, and baking soda will not do an appropriate job raising your water’s pH. You must buy these materials. Fortunately, when calculated on a per-plant basis, they are quite cheap.

Item Rough cost Cost per plant
A growing medium for germination and support $10.00 $0.10
Fertilizers and minerals used to create the nutrient solution for the plants $50.00 $0.022
Purified water $0.00 $0.00
Chemicals for adjusting the pH of the water $15.00 $0.063
Seeds – plan on planting 4 per cup $5.00 $0.02
Total up-front: $70.00
Total cost per plant*: $0.20
* (this calculation is for lettuce – fruiting plants will cost more)

How Do You Grow Plants With the Kratky Method?

That’s what this series of articles is all about! In it, we will guide you through the steps towards your first Kratky grow. We will use the crop that the Kratky method was designed for – lettuce. The skills you develop and following the instructions in the articles that follow will then allow you to pursue growing a wide variety of crops using the simplest for of hydroponics.

 

 

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