Another name for a mason jar hydroponics system is the Kratky method or Kratky hydroponics. By some, it’s considered the 7th hydroponic system, the cheapest and easiest of them all.
In reality, if you’re searching for types of hydroponics systems, more often than not, you’re not going to find it on the list. You’ll only learn about the ones used by commercial growers, like DWC, wicks, NFT, ebb and flow, drips, and aeroponics.
I should tell you right from the start that, if you want to grow bigger plants with the Kratky method (tomatoes, cucumbers, peppers, eggplants), then you should replace the mason jars with a 5-gallon storage tote. The principles and the method stays the same, only the container is different.
Mason jars work very well as containers for smaller plants: lettuce, leafy greens, herbs, strawberries.
Kratky Method: Mason Jar Hydroponics Components
1. Jars: Bedoo Wide Mouth Mason Jars 32 oz
If you don’t want to buy quart jars with wide mouths, maybe you have some bigger jars around the house, maybe from some coffee that you bought or things like that.
2. Rockwool cubes: 1.5” Rockwool Starter Plugs for Hydroponics
These are the easiest and the most accessible for germinating seeds in but you can also use oasis grow cubes.
3. 3-inch net pots: Vivosun 3 Inch Net Pots
These are the little cups that are holding the rockwool cubes with the seedlings. This is the component that sustains the plants while they’re growing to maturity.
4. Hydroton (expanded clay pebbles): Hydroton Original Clay Pebbles
In order to make the rockwool cubes with the seedlings stable in the 3-inch net pots you should add some clay pebbles at the bottom of the net pots.
5. Nutrient solution for hydroponics: Masterblend 4-18-38 Combo Kit Fertilizer
This is what makes the plants grow, it’s what we call hydroponic nutrient solution. It’s absolutely fundamental to hydroponics. You’ll usually fill up the jar with water and nutrient solution just once and then let the roots take what they need. As the level of the solution decreases, the roots will also receive oxygen.
6. Grow lights: Vivosun T5 Grow Lights 2 ft
If you can’t place your jars somewhere to receive about 6-8 hours of sunlight each day then you’ll have to buy some grow lights to replace that natural light. Grow lights are especially necessary during the winter.
Kratky Method: What Is Mason Jar Hydroponics?
The principle of the Kratky method is very simple: there are no moving parts to this system.
There’s no need for water pumps or air pumps or anything like that. This is why the Kratky method can be considered one of the simples, most rudimentary hydroponic systems.
The seedlings’ roots in their growing medium are immersed in water. The water contains hydroponic nutrient solution (plant food). As the plants continue to grow, the water + nutrients levels decrease. The gap between the water and the roots is what oxygenates the roots.
It’s very simple and one of the best ways to learn about hydroponics.
The Kratky method can use mason jars as containers but you can also choose to grow in a 5-gallon plastic storage tote. It depends which is easier for you. If you want to grow bigger plants, you can’t do it in mason jars.
In this article we’re going to talk about how to hydroponically grow herbs in mason jars. Lettuce and leafy greens can also be grown in this set-up. And a few other plants. Even strawberries if you want to try something a bit more demanding of your time and attention.
If you want a visual guide on how to grow plants in a mason jar, check out this YouTube video, it’s really nicely made.
Mason Jar Hydroponics Main Components
- quart jars with wide mouths (32 oz)
- rockwool cubes for germination
- 3-inch net cups
- expanded clay aggregate (hydroton) as the additional growing medium
- nutrient solution for hydroponics
- LED grow lights full spectrum
I definitely recommend buying the wider mouth mason jars because they offer plants plenty of room to grow. They will also go perfectly with 3-inch net cups.
The important thing to remember is that the net cups must fit perfectly over the mouth so that nothing can go through into into the water.
If this is your first attempt at hydroponics, I recommend buying a nutrient solution for hydroponics and following the instructions that are written on the packaging for mixing and how much to use.
It’s the easiest way and a hydroponic solution in powdered form might seem expensive at first but it will last a long time. Some instructions will just have you dissolve a spoon per one gallon of water. It really depends on what nutrient solution you’re buying so, read the instructions and follow those precisely.
How to Grow Plants with Mason Jars Hydroponics
Let’s see which are the basic steps that we have to follow if we want to grow plants in mason jars from just water and nutrients.
1. Germinate seeds
Germinate the seeds in rockwool cubes. Rockwool cubes are the easiest to use and you won’t have to remove the seedlings from the cubs when it’s time to transplant them into the net pots.
The easiest way to understand how seeds are germinated in rockwool cubes is by watching a YouTube video.
I also included a guide on how to germinate seeds in rockwool cubes in my article on how to grow basil from seed. The steps are pretty much the same for all kinds of seeds. Some seeds might require soaking so you should definitely check that out.
You can also attempt growing herbs in mason jars from cuttings in which case you don’t need to germinate the seeds but, for plants like lettuce, you need to walk the long road, starting with germination in rockwool cubes.
2. Transplanting seedlings
When the germination is done, it’s time for transplanting.
You should transplant the seedlings together with the rockwool cubes, there’s no point in removing the seedlings from the cubes.
3. Type of jars
The best are 32 oz quart jars with wide mouths.
The number of jars will match the number of rockwool cubes with seedlings.
You can also use smaller jars but there’s one thing you need to pay attention to depending on the type of jars you’re using to grow plants: the size of the net cups.
4. Net cups
Get 3 inch net cups for quart jars with wide mouths.
Get 2 inch net cups for smaller jars with a smaller mouth.
The net cups are the place where you will transplant the rockwool cubes with the seedlings.
5. Expanded clay aggregate pebbles
If you’re using 3 inch net cups you should also add some expanded clay aggregate pebbles to keep the rockwool upright and stable.
6. Nutrient solution
You can buy it or you can make your own if you want to save even more money.
For beginners, I recommend buying the nutrients.
There are a lot of hydroponic nutrients to choose from: Masterblend 4-18-38, General Hydroponics Flora Grow, Bloom, Micro Combo Fertilizer Set, Dyna-Gro Foliage-Pro, etc.
7. Grow lights
You can use T5 bulbs or LED grow lights. T5 bulbs are fluorescent lights. They can be very effective and cheaper than LEDs. Still, LEDs remain the best but T5s are also wonderful for leafy greens, herbs, and microgreens.
These are essential if your jars don’t have access to sunlight or if you’re growing in the winter, as well.
However, if you can place your plants under sunlight and you’re only growing in the warmer months, then you won’t need any type of grow lights at all.
If you want to teach your children about how to take care of an indoor garden, this mason jar hydroponics system is the perfect method. You’ll have so much fun as a family.
If you’re committed to doing your best, you should also consider getting a pH meter or a pH control kit. For fine-tuning the hydroponic solution, you can buy pH Up and pH Down bottles.
You can also go the traditional route of growing plants in mason jars, you can fill them up with soil instead of water. This website has a good guide on that. I am a bit concerned that there’s no drainage for the soil but they say that they use small pebbles or stones .
Kratky Method: Grow in Mason Jars Hydroponics in 6 Steps
1. Fill in the jars with water and nutrient solution.
2. The water with nutrient solution should reach just above the bottom of the net cups, 1 inch above is good, the growing medium (hydroton + rockwool cubes) will fill up on water and nutrients and feed them to the roots of the plants.
3. Wrap up the jars in colorful paper to prevent algae growth – you can also use aluminum foil to reflect the light or you can spray paint them.
4. Place the mason jars in direct sunlight on the window sill or use LED grow lights if you don’t have access to direct sunlight.
5. As the roots and plants grow, the water and nutrients level will decrease – this depletion of water is what will provide the roots with the needed oxygen.
6. The water and nutrients are usually not replenished as the plants continue to grow but you can also add some more if your plants are still not ready for harvest and the roots are running out of water and nutrients. It depends on the type of plants that you’re growing.
Plants You Can Grow in Mason Jars Hydroponics
In terms of plants you can grow in hydroponic mason jars, the choice is more varied than you might expect. A wick system will be a bit more restrictive than the Kratky method.
- lettuce is the first you should try growing in mason jar hydroponics systems – I recommend starting off with lettuce varieties like loose leaf lettuce, butterhead, romaine or lollo
- spinach is another leafy green that will give a good yield – you can expect to harvest spinach in about 40 days, since germination only takes about a week, or, if you want to harvest it as baby spinach, it only takes about 15-20 days
- bok choy
- herbs (basil, mint, parsley, cilantro, thyme, chives, rosemary) – after leafy greens, herbs are the second best choice to grow in hydroponic mason jars
- hot peppers
- cherry tomato varieties – they’re not as easy to grow as leafy greens and herbs but it’s possible to grow them in mason jar hydroponics, although bigger containers will do much better with cherry tomatoes; depending on how quickly the water is consumed, you might need to replenish it with nutrient solution once a week or once every 2 weeks
- strawberries – they require more attention because a pH level of 5.5 to 6.2 is needed and they need to be pollinated by hand by brushing pollen from male flowers into female flowers
Why You Should Consider Mason Jar Hydroponics
The Kratky method realized with mason jars as containers is one of the easiest and most accessible hydroponic indoor arrangement.
This is a lot like the deep water culture system with buckets as containers but without the air pump and air stone. The Kratky method can also use buckets as containers instead of mason jars.
But if you’re using mason jars to grow plants hydroponically, it’s on a much smaller scale so, it can fit in smaller spaces. Deep water culture buckets are usually placed in a garage or in a greenhouse.
If you want to experience hydroponics but don’t want to spend money on a hydroponic indoor garden, which can be quite expensive, I definitely recommend turning to mason jars hydroponics.
Mason jars are definitely the inexpensive alternative to hydroponic indoor garden kits, like the ones from iDoo or AeroGarden.
You have the possibility of growing as many plants as you want, as many as you can fit in your house or apartment.
This is actually a perfect simple hydroponic system for apartments and beginners, you can have your own mini-garden indoors even if you don’t live in a huge space.
Another major advantage is that this simple system doesn’t involve any moving parts. There’s no need for water pumps, air pumps, air stones or tubing.
If you want to graduate to a superior level of hydroponics systems, you will move on to DWC or wicks or NFT or ebb and flow or drips. The Kratky method with mason jars can be your stepping stone.
Mason Jar Hydroponics FAQs
Let’s make a small recap on this post by answering a few interesting questions on mason jar hydroponics. You will be able to understand this simple system even better.
Q. Can I grow lettuce in mason jars?
Lettuce is actually one of the first vegetables that people start growing hydroponically. It’s a plant that loves water so, it’s absolutely perfect for growing in mason jars filled with water and nutrient solution. Growing lettuce in hydroponic mason jars doesn’t require a lot of work or any special requirements: it has a permissible 6.0 to 7.0 pH, it’s a cool plant that should be grown in temperatures under 75 degrees F, and it requires 16-18 hours of LED grow lights.
Q. How do you make a hydroponic herb garden mason jar?
The main components for making a hydroponics herb garden mason jar are: quart jars with wide mouths (32 oz), rockwool cubes for germination, 3-inch net cups, expanded clay aggregate (hydroton) as the additional growing medium, nutrient solution for hydroponics, LED grow lights full spectrum. If you’re growing the herbs from cuttings, you can skip germination in rockwool and grow the cuttings in aggregate clay pebbles directly.
Q. Can you use mason jar for plants?
Yes, you can use mason jars to grow plants indoors in soil or you can use them for making a simple, cheap hydroponic system.
Mason Jar Hydroponics Cheap Alternative
If you want another DIY rudimentary system, the best alternative to mason jar hydroponics is making a wicks system from plastic bottles as containers.
The advantage with plastic bottles as containers is that you don’t need to buy net cups. The upper half of the cut plastic bottle will serve as the place where the clay pellets with the rockwool cubes are placed.
And you don’t have to spend any money on jars.
You can watch several YouTube videos on this method, as well. So, if you’re not ready to invest in some quart jars with wide mouths for the Kratky method mason jar hydroponics, you can try the wick system in plastic bottles.