What is the Kratky Method of Hydroponics?
The Kratky method is a hydroponic method where the plants grow in water rather than in soil. It is probably one of the simplest hydroponic methods and is perfect for those living off the grid because it takes no electricity at all. What makes the Kratky method unique is its simplicity. There is no aeration, no water movement, and generally no reason to change the nutrient solution if you have set everything up correctly and you are only growing leafy greens.
If you are growing flowering or fruiting plants, then you will need to add nutrients and water as it is used up by the plant. The pure form of the Kratky method does not call for adding more water or nutrients. It is a more set it and forget it method.
How Well Does the Kratky Method Work?
Here are some lettuce plants grown using this method. Arugula is an excellent green to grow as it grows very quickly. The Kratky method is an excellent method for growing leafy green vegetables. Fruiting plants are a little more difficult but it can be done.
Here’s a cucumber plant. There are flowers starting to develop on this plant after three months of growing in this container and here are the tomato plants – but more about this later.
So basically the Kratky method is a method of growing plants in water without any special equipment. It was developed by Bernard Kratky from the University of Hawaii. He called it a “non-circulating hydroponic method” but has now become universally called the Kratky method.
The Simplicity of the Kratky Method of Hydroponics
So how does it work? Well, to get started, you need a plant or a small seedling. I usually start my seedlings in Rockwool. Below you can see what Rockwool looks like. As you can see it come in small cubes with holes to put the seeds in. This package has one and a half-inch cubes. They come in different sizes but I find this size works for my uses here.
Rockwool is made from basalt, rock, and chalk that are melted at 1600 degrees Celsius into lava, which is then pulled into cotton candy-like fibers. The fibers are then compressed into these cubes. The high temperature that produces the Rockwool renders it sterile, so it is perfect to use as a growing medium. You will need to soak the Rockwool in water until it is saturated and then just drop a seed down the hole.
Once you have seedlings as you see here, you are ready to transplant.
How to Plant Using the Kratky Method
Now, if you’re using traditional planting methods, this is where you would put the plant into soil, but not with the Kratky method.
We take the young seedling in its Rockwool cube and plant in water. Instead of using a net cup like this, you can you’re your own net cups using plastic drinking cups, but these are easily available on Amazon and are not expensive. I have them in two sizes.
Here you can see the two-inch net cups for smaller plants. These fit nicely into the smaller Mason jars and are perfect for my lettuce plants. You can also see the three-inch net cups that fit into the larger Mason jars and also fit perfectly into this Folgers coffee container. When I found out that the three-inch net cups fit into the Folgers containers, I was very excited.
These containers have a small little window so I can check up on the water level and they are larger for my larger plants. What a great way to recycle!
Still in the rock wool, I put some clay pebbles around the Rockwool to fill in the empty space and to keep light from getting down into the water. The clay pebbles are not necessary, but they do add stability to the Rockwell cube in the net cup. Now I placed the entire net cup into a jar or some sort of reservoir filled with water.
Mixing Nutrients for Your Plants
The water has a hydroponic nutrient solution to help feed the plants the nutrients they would normally get from the soil. For my lettuce plants, I use the Grow Big Hydroponic solution from Fox Farms. It is really easy to mix. Just shake and add two teaspoons to a gallon of water.
For fruiting or flowering plants like cucumbers or tomatoes, I prefer the Masterblend formula. This is a little more complicated since it has three parts to be mixed. Also, the recipe on the bag gives the amount to be mixed into five gallons of water, which is far too much for my needs.
So I use a kitty litter plastic container and measure two gallons of water into it and then add half of the recipe called for. So, following the recipe at half the measurements, I add the six grams of calcium nitrate, first. Then I mix it with the water so that it dissolves completely and then I add six grams of the Master Blend 4-18-38 formula and dissolve that completely. Next goes in the three grams of magnesium sulfate (or Epsom Salts) and again dissolve it completely. Now it’s ready to be added to whatever containers I am using – in this case, the glass Mason jars.
When first transplanting the seedlings, the water level should be to the bottom of the net cubes. As the plant grows, it will drink up the nutrient-rich water and the roots will grow down into the water as you see below. As the water level goes down, the plant will put out what are called air roots and these roots help feed the plant the oxygen that it needs.
Don’t Drown Your Plants!
That’s why with this method, you don’t need an air pump. Now, if you are growing lettuce or leafy greens, this method is perfect because, by the time the water is used up, the leafy greens will be ready for harvesting. However, if you are growing fruit or flower-bearing plants they take longer and so the water will need to be replenished. When you do that, you risk drowning the plant.
If you refill the reservoir level too high, make sure when you refill it to leave a good two inches of space for the plant roots to breathe. This is the number one reason plants die after the water level is replenished.
The plant’s main roots should be long enough to reach the water and the plant’s air roots should stay out, otherwise, you will drown your plant.
The cucumber plant is flowering and will soon produce cucumbers. Here you can see the tomato plants that have also started to flower and even have two little tomatoes on them. In addition, there is the lettuce that just keeps growing and growing!
Conclusion – What is the Kratky Method of Hydroponics?
The Kratky method of hydroponics takes no moving parts, no electricity and can be built on easily recycled or inexpensive materials. It’s great for those of us that are trying to get back to our roots and just plain don’t want to spend buckets of money growing food! You will see the basics you might want to buy on the Amazon site strip below but this system can be set up for $20 or less. I love this system because of its ease of use and the set it and forget it method. I think you will love it to!
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