So you want to explore the world of hydroponics? The sheer number of options to choose from—not to mention setup costs—can overwhelm serious hobbyists and commercial growers alike. Don’t despair, though: it’s possible to build your own hydroponic system in under an hour. That’s where the Kratky Method comes in.
Most hydroponic methods require pumps to circulate nutrient solution. Others require air pumps and air stones to bring enough oxygen to plant roots. Most installations also require plumbing, big tanks, and lots of electricity. Rather than going the standard route, e.g. DWC, NFT, Bato buckets, ZipGrow, Aquaponics, and, Aeroponics, there’s an easier way. Read on to find out more.
What is the Kratky Method?
B.A. Kratky is a horticulturist researcher at the University of Hawaii. In 2004, he published a paper titled “A suspended pot, non-circulating hydroponic method.” The Kratky method was born.
It’s a cheap and simple way to get into hydroponics. No electricity, no pumps, and no fancy equipment are needed. You can get started with a few simple household items and one trip to your garden store.
The simplest setup requires a 1-gallon, food-grade container with a top, as well as water, hydroponic solution, growing medium (like perlite or rockwool), and a mesh growing pot. More on that later.
How does it work? Basically, little net pots are suspended over a tank of stagnant hydroponic solution so that only the bottoms of the pots touch it. The growing medium in the pots absorbs water and nutrients. As the plants grow and absorb more and more solution, the liquid level in the tanks drops. Now only the roots emerging from the pots reach into the solution. The roots in the air space between the cover and the solution breathe the oxygen there.
Harvest time comes before the solution runs out. The growers can then clean the tanks and start over. The simplicity and low cost of the Kratky method make it an interesting system for hobby farms and weekend gardeners. Of course, it’s not a one-size-fits-all solution.
Pros and cons of the Kratky Method
Like every growing method, the Kratky method has its strong points and its downsides. It’s worth doing your research to explore those before you commit your time, resources, and plants to Kratky’s way of doing hydroponics.
Pros:
Simplicity
The Kratky method is dead simple. You can build it in a 1-gallon container to house and grow one plant in just a few minutes. If you’d rather grow 60 heads of lettuce at once, you could build a 4’x8′ tank with some lumber and vinyl sheets in about 20 minutes. (Keep reading to find out how to make that happen.)
Passive system
It’s a passive, set-it-up-and-forget-it system. In other words, it requires no electricity and minimal monitoring. Your plants won’t die if there’s ever a power outage, equipment breakdown, or a much-deserved weekend getaway on your part.
Cheap
The system has no moving parts, uses no electricity, and takes little time to set up. It’s a very affordable way to try your hand at hydroponics.
Adaptable
The Kratky method is easy to adapt to many situations. If you need to avoid stoop labor because of a bad knee, you can set the tanks up on a table. It can be as small as a gallon, or as big as a commercial greenhouse. You can adapt it to suit any need or growing space.
Cons:
Not for all veggies
It’s great for leafy greens like lettuce, arugula, spinach, and watercress. Herbs like basil and oregano will also thrive with this technique.Unfortunately, the Kratky method isn’t so great for fruits or root vegetables.
Fruit-bearing plants like tomatoes or beans need way more nutrient solution to provide an interesting harvest. You’d need 25 to 40 liters of water to produce about 1kg of tomatoes. As such, it’s not worth the investment to grow them this way.
For root vegetables, the problem lies in that roots need to extend out of the pot to reach the nutrient solution. That’s not ideal for carrots and beets, to say the least.
Vulnerable
A system based on the Kratky method has a few inherent vulnerabilities.
The system’s stagnant water can make it a perfect breeding ground for algae, bacteria, and insect larva. To limit such problems, it’s best to choose opaque containers. Paint the outsides of the containers or line the insides with black vinyl sheets (like pond liner) to prevent algae blooms.
Smaller tanks and elevated tanks will be more prone to temperature variations. If you live in a warm climate, this might be a non-issue. But in colder climates, a cold snap could spell the end for your plants.
Your tanks need protection from the elements. Mainly, you really don’t want rain to dilute your precisely calibrated nutrient solution. For best results, find a spot with lots of indirect sunlight and a roof—like a lean-to, a balcony, or a gazebo.
How to get started with the Kratky Method
The 1-Gallon Bottle
Materials:
- Food-grade 1-gallon container with a lid
- 1 gallon of water
- pH kit
- Hydroponic solution
- Perlite or rockwool
- A mesh growing pot (about 2” wide)
- Cutting tool (hobby knife, reciprocating saw, hole saw)
- Seeds (lettuce, mustard greens, arugula, spinach, herbs)
Steps:
- Cut a hole in the container lid. You want the hole to be slightly smaller than the width of the mesh growing pot. The idea is for the pot to fit mostly through the hole without falling through.
- Check the water’s acidity level and adjust it accordingly. The pH level should be between 5.5 and 6.5. Use pH Up or pH Down to adjust your water’s pH accordingly, if that’s required.
- Prepare your hydroponic nutrient solution according to instructions. Fill up the container almost to the top. Then put the lid on and insert the growing pot in the hole. Only the bottom half inch should be immersed in the solution. Adjust water level accordingly.
- Fill the mesh growing pot with the growing medium, and then put it in the lid hole. The medium will absorb water and nutrients via capillarity. Once it’s damp, sow a few seeds.
- When the first seedlings sprout, choose the hardiest and eliminate the others.
After a few weeks, you should have a beautiful plant ready for harvest. You can harvest all of it or pick a few leaves at a time when needed. Once you’ve harvested, you can clean the container and start over again.
The Plastic Bin Tank
Materials:
- Plastic tote with lid (I like the ones that fit under a bed)
- Enough water to fill the tote
- pH kit
- Hydroponic solution
- Perlite or rockwool
- Mesh growing pots (about 2” wide)
- Cutting tool (hobby knife, reciprocating saw, hole saw)
- Seeds (lettuce, mustard greens, arugula, spinach, herbs)
Steps:
- Calculate how many plants you can grow in your tote. Here’s a quick rule of thumb: each plant requires one gallon of nutrient solution. Most totes’ size is given in volume (gallons or liters). Then, cut holes in the container lid. Space the holes equally so that each plant gets as much growing space as possible. Make the holes slightly smaller than the mesh growing pots so they fit without falling through.
- Follow steps 2 to 5 above.
A few notes on this setup: Make sure to fill up the tote after it’s set up in place. It’ll be very heavy once filled. Also, deeper totes are better than shallow ones. They may require more solution, but they hold more stable temperatures throughout the day.
Finally, the surface on which the tote rests must be level. Otherwise, you’ll end up with an uneven crop. One end will have drowned seedlings where the solution was too high, and the other will have wilted seedlings where the solution was too low.
The 4’x8’ Wooden Frame Tank
Materials:
- 3 planks of lumber – 2”x6”x8’
- 4’x8’ plank of 3/4” plywood
- Tools and hardware (circular saw or hand saw, drill, screws, nails or tacks)
- 0.15 mm-thick black polyethylene sheeting (about 100 sq ft)
- 2 hydroponic rafts (4’x4’ “lid” with 2” holes for plants)
- Duct tape or large painter’s tape
- Enough water to fill the tank
- pH kit
- Hydroponic solution
- Perlite or rockwool
- Mesh growing pots (about 2” wide)
- Seeds (lettuce, mustard greens, arugula, spinach, herbs)
Steps:
- Cut one of the 8’ planks in half. Use the two 8’ planks and two 4’ planks to build a 4’x8’ rectangular frame. Screw the 3/4” plywood on top, then flip the whole tank over. Line the tank with 2 layers of black polyethylene sheeting and use nails or tacks to fix it to the top of the frame.
- Follow steps 2 to 5 above.
The same precautions as with the totes apply to the wood frame. As noted before, it’s best to avoid any light reaching the solution. Algae would love to proliferate in that nutrient-rich water. Use duct tape or large painter’s tape to seal around and between the rafts.
If you experiment with the method, or have already done so, drop us a line to let us know how it worked for you.