Kratky Hydroponics

Do you want to grow some plants hydroponically and you want a simple gardening method? Then Kratky hydroponics is for you.

Are you new to hydroponic gardening and you want to “dip your toes” with a simple method? If you are after a really low tech method, then nothing is simpler than Kratky hydroponics.

What is the hydroponic Kratky method?

The Kratky method is a non-circulating hydroponic technique, where you simply grow plants with their roots dipping in the nutrient solution. It requires no technology at all and it is very simple to set up; however, it is not the best hydroponic method by far, as it has many limitations.

If you read on, you will find what Kratky hydroponics means, how you can set it up, how you can run it, but also its disadvantages and drawbacks.

What Is Kratky Hydroponics?

What Is Kratky Hydroponics_

The Kratky method is the simplest and most rudimental of all hydroponic systems. You will simply need a vessel for your nutrient solution. You will then place your plant so that the roots dip in the solution and the aerial part of the plant is dry.

It is basically a living plant in a jug. This may be a simplification, but it will give you the basic idea. You must have seen it done with some bulbs like hyacinths, or sweet potatoes… Pothos too is commonly grown with the Kratky method.

When you see a jug, a vase, even a simple glass with roots in it and a plant growing out of it, well, you are looking at Kratky hydroponics.

What You Need for Kratky Hydroponics

What You Need for Kratky Hydroponics

The main advantage of Kratky hydroponics is that you basically need no equipment, and that you can set a small garden up with a few jugs, bowls, glasses or even an old bottle you were about to chuck in the bin.

You will not need any pumps or any pipes etc. However, it may depend on the shape and size of your plants; the key problem with Kratky hydroponics is making sure that only the roots dip in water.

Keeping the Aerial Part of the Plant Dry

Keeping the Aerial Part of the Plant Dry

The aerial part of the plant is what in Nature is above ground: from the base of the stem or trunk to the tip of leaves or flowers.

Basically, everything apart from the roots of your plant. This part should not be immersed in water, because it may, and probably will, rot.

Roots, on the other hand, can dip in water or the nutrient solution and, with the Kratky method, they will have to, because this is how they will feed.

Now, imagine a bowl, like a salad bowl for example. How can you put a plant in there and make sure it does not fall into the water or nutrient solution? There are three ways of making sure that the plant’s areal part stays dry:

  • The shape of the vessel; jugs and vases with a small opening, especially with a narrow neck, allow you to insert the roots in the nutrient solution and keep the rest of the plant above the opening.
  • The shape of the plant; if your plant has a bulb, it will be easy to choose a vessel with an opening that is just slightly smaller than the bulb itself. In this case, you can even choose a perfectly cylindrical vessel. This is one of the reasons why hyacinths, amaryllis and even daffodils are often grown (and sold) in Kratky systems.
  • Using a holding structure; you can use a net, a few sticks or toothpicks, or even a flexible rubber collar to stop your plant from sinking into the jug, vase or bowl.

Can You Use Kratky with Just Water?

Can You Use Kratky with Just Water

You can use Kratky hydroponics without the nutrient solution and in fact, many gardeners and amateurs do. You can simply fill the vessel with water.

If you go around stores and people’s homes you will find plants growing in jugs, vases etc. with just water in them. This is possible, but it does have some disadvantages:

  • The plant risks being undernourished; of course, water is never pure water, so, even tap water has some nutrients in it. But these are often insufficient and in the wrong proportions for most plants.
  • Not all plants can grow without a nutrient solution; using water only is feasible mainly with plants that have a short life cycle, like bulbs, in fact, that have a long dormancy. Bulbs in particular have lots of energy stored in them, and this means that they will survive even without nutrients. But bulbs also grow stems when they are in your laying around…
  • Even with bulbous plants, the plant will weaken; your amaryllis or hyacinth will use up a lot of the energy stored in the bulb. It will blossom, true, but then it won’t be able to send energy back into the bulb. This means that it may well be the last time it gives you flowers.
  • The health of your plants depends heavily on the quality of your water; if you have “bad water”, poor in minerals, too alkaline etc. it will affect how your plant grows.

So, while it is very common indeed, if you want to be just a bit professional, use a nutrient solution.

Using the Nutrient Solution

The key concept of hydroponics is not actually growing plants in water, but in a nutrient solutionof water and nutrients.

So, learning how to prepare the solution is key to having a successful hydronic garden.

You don’t need to prepare the nutrients yourself; you can simply buy them from any garden center or online, and you can choose among a wide range of nutrient mixes, from those that better suit acid loving plants, those for blooming plants, etc.

Preparing The Nutrient Solution

You will not need much of the nutrient mix to prepare the solution; it is a matter of “spoonfuls”, not “tanks”, to give you an idea of the order of measurement.

So, this means that growing plants hydroponically, even with the Kratky method, is very cheap.

But how can you go about it?

  • First, measure how much water you vessel contains. To do this, fill it with water and then pour it into a measuring jug. You will need this to calculate the quantity of mix you will need for your solution.
  • If you are using a growing medium, make sure you measure the water after you have put it in the vessel.
  • Then, in a different container, which is easy to stir, pour the water. Kratky containers are usually difficult to stir.
  • Add the nutrient mix according to the volume of water. Usually, it is one ounce per gallon, or 7.5 grams per liter. Just check on the bottle and it will tell you how much exactly for the one you have chosen.
  • Stir well. This is very important to make the solution, which you want to be as uniform and even as possible.
  • Finally, pour the nutrient solution into your Kratky vessel.

As you can see, this is very simple. Now, you are ready to put your plant in place. That’s about it!

Using a Growing Medium with the Kratky Method

Using a Growing Medium with the Kratky Method

You can greatly enhance the performance of your Kratky garden by using a growing medium. This is an inert and porous material, usually in fibers or pebbles, that will absorb the nutrient solution and then release it slowly.

A growing medium also improves the oxygenation of the roots, and this is a major flaw with the Kratky method, as we will see.

A growing medium has three main advantages:

  • It soaks up some of the nutrient solution and releases it slowly.
  • It has small pockets of air, helping the aeration of the roots.
  • It slows down the evaporation of the water in the nutrient solution.

So, it is advisable to use a good growing medium. There are many available; some absorb more water than air, others the other way round. 

With Kratky, a mix of perlite and vermiculite is quite good, because vermiculite holds on to pockets of air, which helps the roots of your plant breathe.

You can, alternatively, go for fibers like coconut coir; these too are good at holding on to air as well as the nutrient solution.

If the growing medium has small pores they will hold air, if they are big, the air will run away, but they will be better at holding water and liquids. So, a mix of different pores is the best, and natural fibers have pores of varying sizes.

Advantages of the Kratky Method

The Kratky method has some advantages, and some are quite surprising considering that it’s a very basic hydroponic system.

The Kratky Method Consumes Little And Produces A Lot

The Kratky Method Consumes Little and Produces a Lot

The Kratky method has an outstanding consumption to production ratio! This is amazing, but in terms of nutrients consumed, the Kratky method produces more plant mass (therefor crop) than most other methods, bar only aeroponics in fact.

This is possibly because it is a fully passive method and plants absorb all the nutrient solution.

The Kratky Method Is Easy

The Kratky Method Is Easy

By now you know that the Kratky method is very easy to set up and it requires very little to get it going.

Setting up a complex hydroponic system like ebb and flow can be quite daunting for newcomers to this type of gardening.

So, if just want to get the gist of what hydroponics means; if you just want to have a little experience of growing plants this way, the Kratky method is by far the simplest choice.

The Kratky Method Is Cheap

Not only will you save money in equipment if you choose the Kratky method, but also in electricity, nutrients and even water.

A simple system is cheap to run as well as to set up. In fact, it can cost you nigh on nothing to grow a plant in an old wine jar…

The Kratky Method Is Very Low Maintenance

The Kratky Method Is Very Low Maintenance

The more elements you have in a system, the more you need to look after them, and that means maintenance.

Inspecting the different parts of a complex hydroponic system is not very hard, unless you go professional, but it does require some time.

With the Kratky method, you have virtually no maintenance at all; you only need to check that the water solution is not running too low and that your plant is healthy…

What is more, there is no risk that electrical parts may break. If you have a water pump, an air pump, pipes and hoses, two different tanks, a timer etc. as you do with other hydroponic system, each element can break, develop faults etc.

No need to worry about all these if you choose the simple Kratky method.

The Kratky Method Looks Good

This method has a great decorative value for indoor plants and this is one of the reasons why it is becoming very popular.

A beautiful, original bowl or glass vessel with an architectural houseplant growing in it has its charm on a desk or on a bookshelf.

It is easy to see how you can use it for an oriental look, a minimalist space, a futuristic one or any other creative and elegant ideas you may have for your indoor space.

Disadvantages, Limitations and Drawbacks of the Kratky Method

The Kratky method is very simple, but it is riddled with limitations, drawbacks and disadvantages. It does not compare to advanced hydroponic methods like aeroponics, ebb and flow or the drip system. Still, in some areas, it punches way above its weight…

In any case, you need to be aware of the disadvantages of this method before you make a decision. And here they are.

The Kratky Method Works Only On A Small Scale

You cannot have a whole big professional garden with the Kratky method. Basically, you can only use it with some plants and usually with individual plants in each vessel.

In theory, you can group a few plants together, but even in this case, you may have some problems:

  • If a plant dies before the others, it may spread disease.
  • If a plant catches a disease, it will spread to others.
  • It is actually technically difficult to grow a group of plants with this method.

So, the Kratky method is mainly limited to the decorative bowl or vase with a small plant in it.

The Kratky Method Is Viable Only For A Few Plant Varieties

The Kratky Method Is Viable only for a Few Plant Varieties

You cannot use the Kratky method with big plants; it is limited to those plants that have a root system that can withstand poor aeration, plants that have short life cycles and small size plants. You can grow lettuce, some flowers, small vegetables and plants, but deep root vegetables will rot, big plants will need a much more efficient system and long lasting plants will die for the lack of oxygen to their roots.

The Kratky Method Has Aeration Problems

The Kratky Method Has Aeration Problems (1)

It is hard to stress how important is oxygenation the roots of your plants in hydroponic gardening. And this is almost impossible with the Kratky method.

In fact, most major breakthroughs with hydroponics have to do with better ways of providing air to the roots, not water or nutrients. Instead, the Kratky method is very rudimental and it is really weak on this side.

You can partly improve the aeration with a growing medium, as we can see, but nothing matches the use of air pumps, irrigation cycles and even spraying droplets as you do with aeroponics.

So, the risk is that your roots will literally suffocate, and the plant may die.

The Kratky Method Has a Stagnant Nutrient Solution

When water is stagnant, it becomes a perfect breeding ground for pathogens that carry disease. There is no way you can provide running water with the Kratky method, so, your plants are at risk of contracting ailments carried by bacteria.

This becomes even worse if:

  • You grow plants together, because if one catches an infection, it will quickly spread it to the others.
  • You grow plants that have different cycles; if you grow a plant that ages and becomes weak, maybe some of the roots start rotting, while another plant in in its prime, even the young and healthy plant will risk getting infected.
  • You grow long life plants; if the nutrient solution stagnates for weeks, the chance that bacteria and pathogens will find it a good place to reproduce is much lower than if it stagnates for months, of course. with this method.

It Is Hard To Change Or Top Up The Nutrient Solution

The Kratky method, unlike others, does not have a two tank system, one, the reservoir, where you keep the nutrient solution and the other that you use to grow and irrigate your plants. This is a major disadvantage.

In fact, you cannot top up the nutrient solution easily and, in case it runs out, you need to remove the plant or plants, wash the vessel and then replenish it.

Even just adding water can be hard if the plant has a large stalk and leaves, as you may find it difficult to spot an access point for the water among the leaves and stems…

It Is Hard To Check The PH And EC Of The Nutrient Solution

Plants like different pH ranges, and the electric conductivity level of the water tells you if the plant needs nutrients and even if there is excess of nutrients in the solution.

The problem with the Kratky method is that you do not have a reservoir where you can easily dip in the pH meter and EC meter.

You would need to put it into the only vessel you have, and this, again, means finding an aperture among leaves and stems, and one that allows you to reach the nutrient solution.

This means that you cannot keep a close eye on the quality of the nutrient solution, therefore on the health of your plant itself.

The Nutrient Solution May Evaporate

There is no reservoir of nutrient solution with the Kratky method, as you know, and this means that if the water evaporates, or it gets totally absorbed by your plant, you have no automatic way of replenishing it.

So, what happens if you do not notice that your plant is running dry? You risk leaving your beloved green friend thirsty and hungry, and this may cause lots of problems, as you can imagine.

Yet even if you notice the problem, we have seen topping up the nutrient solution or changing it can be a problem with the Kratky method.

The Kratky Method: Simple and Fun, but Not Perfect

On the whole, the Kratky method is good to grow the odd plant on your window sill or to adorn your bookshelf.

It is by no means suitable for a professional garden, but it can fascinate your children and develop their interest in plants and hydroponic gardening. From an aesthetic point of view, it has its charms.

It is cheap, easy to set up and to run, but it is very limited in terms of types of plants you can grow, size of garden and purpose of your experiment…

In short, you won’t run a hydroponic farm with the Kratky method…

But there is maybe one element of this method that makes it a bit special. It can also be a good teaching tool…

In fact, the very first plant I ever grew was with the Kratky method… We were at elementary school and my teacher taught us to grow lentils in a plastic tray and with a simple growing medium, cotton.

I still remember the little plants on the window sill… Maybe that’s why, many decades later, I decided to become a gardener… Who knows?

Adriano Bulla

Written By

Adriano Bulla

After many years as an academic in London, Adriano Bulla became a writer, publishing books like A History of Gardening, Organic Gardening and Elements of Garden Design; he then decided to become a gardener, following his childhood dream, and has been following his dream writing and gardening professionally in Southern Europe, where he has specialized in new and innovative organic gardening fields and techniques, like permaculture, regenerative agriculture, food forests and hydroponics.

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One Comment

  1. A couple points here which you mentioned are drawbacks of kratky that aren’t really drawbacks.
    1. You can grow many plants here if you use a larger container. This could include rafts but I use 10 or 20 gallon opaque Rubbermaid containers and a hole saw to put the sites in the lid. I put 6 sites per container of lettuce or 8 sites per container for spinach or 4 for kale or 2 for broccoli or cabbage in a 10 gallon container for shallow root plants or 20 gallon for deeper root plants. Grow one type of crop per container because different types of plants will uptake nutrients at different speeds. You can also use a plastic garbage or can or barrel for bigger plants. For even larger systems you can use a foam raft in a container made of 2x6s with plastic lining or similar. Using this method you can grow an entire greenhouse worth of crops by having multiple beds this way. Kratky is a professor at University of Hawaii Hilo and has lots of videos on YouTube.
    2. You can fight root rot by using a small amount of bleach or pool shock in the water. 10 ml of Clorox (bleach is 6% sodium hypochlorite) to 30 gallons of water will do the trick. Pool shock (calcium hypochlorite) is better than bleach because it breaks down into calcium while bleach (sodium hypochlorite) breaks down into sodium, but I haven’t tried pool shock yet because it comes in a powder. These are both better than hydrogen peroxide because the peroxide will evaporate after a couple days but the bleach will last a whole crop.
    3. You can build float valves with a reservoir connected with bulkheads to refill the system automatically when the nutrient solution gets low.
    4. If your container lid is well sealed the evaporation will drip off the lid back into the nutrient solution and create a humid zone where the plant can grow air roots and get lots of air.
    5. I prefer using pool noodle instead of net pots. I learned this method from Mike Dunzee on YouTube. I use a bread knife to cut the pool noodle into 1-2 inch thick rings, then cut a slit in the ring and shove the plant inside using some of the waste pool noodle to hold the plant inside the holes then wedge that into the hole in the Rubbermaid lids.
    6. You can reuse the container a couple crops without cleaning, just replace the nutrient solution. After 2 or 3 times you can clean the container with a pressure washer or scrub with a sponge.
    7. I have been experimenting with growing fruiting crops like tomatoes but you’ll need to refill with a flowering nutrient mix at some point with those types of crops and since they grow longer you will NEED to use bleach like I mentioned earlier.
    Happy gardening!