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You can easily grow Kratky lettuce indoors with the Kratky method. The Kratky method hydroponic system is totally passive and does not need pumps or airstones.
The Kratky method is named after Dr. Bernard Kratky. He was a researcher at the University of Hawaii. In 2009 Kratky introduced lettuce rafts for commercial food production. A lot of lettuce is still being commercially grown this way today.
So we are going to grow Kratky lettuce using his system. I have a video below that shows how I set up my system. It is simple to set up.
You will need a tote and some net pots. You probably will want a hole saw too. And the best thing is once you get it planted all you need to do is sit back and wait for harvest time.
Kratky Lettuce How To Easily Grow Lettuce With A DIY Kratky Method Hydroponic System
I know it doesn’t look like much right now but it will look much better in a week or 2.
I don’t want to overcomplicate the planting part. Coco wicks really well so it is an excellent medium to fill your net pots with.
I was concerned about it falling through into the reservoir. So I ordered some peat pots to hold it.
But I decided to plant my seeds in Jiffy pellets while I was waiting for them to arrive. You don’t need to do this though. You can plant lettuce seeds directly in coco.
Kratky Lettuce Materials List
You can use any tote. People even grow Kratky lettuce in mason jars. I use a 10 gallon Rubbermaid tote. These are ridiculously expensive on Amazon so buy them locally.
I use 3 inch net pots but they are not really 3 inches so you need to cut a 2 7/8 inch hole for them. They would fall through a 3 inch hole.
I use Canna Coco for grow media. I prefer the bricks. They are easier to store and dont harbor bugs.
I use Jacks’s Nutrients. It is a 3 part system. This is a hydroponic system so you don’t want to use organics in it. Mostly it is available in larger sizes but this will work Jack’s 321 Hydroponic Nutrients Fertilizer Plant Food – 2 lb Kit A little goes a long way. 3-2-1 is a ratio and works for cannabis or tomatoes but not lettuce. For lettuce use 1-1-.5 or a tablespoon of the 5-12-26 base, a tablespoon of the calcium nitrate, and a half tablespoon of Epsom salt in 5 gallons of water.
You really want to be at about 800 ppms and a pH of 6.2 for lettuce and that is what I get using my water yours may work out higher unless you are using RO water. That is why I recommend testing your nutrient solution.
This is the meter I use. Hanna Instruments HI 9813-6N Waterproof pH/EC/TDS Temperature Meter
It is not cheap and costs over $200 and you can definitely do your testing for a lot less.
The smaller pens don’t last as long and are nowhere near as accurate but probably good enough for lettuce. Here is a cheap set
While we are waiting for my seeds to sprout I thought it would be good to hear Dr. Kratky explain his system.
You will soon see that lettuce is not the only thing that you can grow with the Kratky method. The sky is the limit to what you can grow with a Kratky system.
The Kratky System Explained By Dr. Kratky Himself
Here is one of Dr. Kratky’s original videos where he explains how the Kratky system works and a link to his YouTube channel: https://www.youtube.com/channel/UCjwBvl5MXuQMziQL2_pQCPA/videos
Kratky Lettuce With Airstones
You absolutely don’t need airstones to grow Kratky lettuce. Still, I think they can make this system even better. The Kratky method is basically a DWC (deep water culture) system but without any airstones.
DWC is one of the fastest growing systems in the world even rivaling aeroponics. It is the addition of air in the root zone and readily available nutrients that make this possible.
Aeroponics does it by misting roots that hang in the air and DWC does it by bathing the roots in oxygenated water.
Considering how cheap adding an airstone is and how little power they use it seems crazy to me not to add one.
The fact it does not need to use electricity makes it very easy to put one anywhere in your apartment.
It also is being used in many poorer countries where power may not be available. So a basic system can make the difference between growing food and eating or going hungry.
But here an air pump can be bought for less than $20 and they use very little electricity. Adding airstones solves 2 problems with the Kratky method.
Some growers do develop root problems for one reason or another. Aeration will keep the roots healthier and plants will grow faster this way too.
The system was designed to only be filled once at the start. Since it develops air roots above the water and feeder roots in the water filling it again will damage and suffocate the air roots.
But with an airstone, you can keep the reservoir at the same level. This means you can top it up periodically. It is even possible to totally change out the reservoir if needed.
Lettuce is a fast growing crop and does not have an extensive root system. But if you want to grow tomatoes or peppers these plants take much longer to bear fruit and they have an extended harvesting season. So the addition of air stones would be highly beneficial.
These lettuce plants will be grown in coco because of its great wicking ability. You might want to learn more about coco Growing Vegetables In Coco Coir Get Amazing Results (indoorvegetablegrower.com)