I have been growing lettuces indoors, in a south facing window or in the green house, for years. These lettuces are grown in window boxes to be harvested when they are bigger than microgreens but smaller than full-size lettuce heads. We use cut and come again varieties such as Cos, Sierra and Red Sails, which provide us with a ton of leafy salad greens throughout the winter months.
Having recently become obsessed with eating a variety of Thai dishes where the food is wrapped in lettuce greens or where the lettuce leaves are used as a utensil, I wanted to get my lettuce to grow bigger. In the window boxes, the plants seemed to burn out or get bitter when I tried to grow them to full size. After reading Jordan Capps’s June 2020 Fifth Season blog about the Kratky method, I became interested in building a larger scale Kratky system that would provide us with many big heads of lettuce, grown quickly without bitterness.
Being a fairly no frills gardener, I found the Kratky system of using no pumps attractive, as I could set the system up in my non-electrified greenhouse. The Kratky system is basically setting your seedlings in a net cup just touching the nutrients in the water reservoir. As the seedlings grow, the water level decreases, forming a highly-humid, oxygenated chamber for the roots to thrive.
Many Kratky systems are designed for a single jar or bucket set up, but I wanted to go big. I wanted to see a carpet of massive, lush, leafy greens, so I decided to invest in a large 20-gallon plastic, lidded storage container from the hardware store. I got this all set up only to stop dead in my tracks when I realized the storage container I chose was not BPA free. When exposed to heat and sunlight the plastic would break down, creating a potentially toxic food growing set up with which to slowly poison my family. Needless to say I scrapped that idea. Then I realized that hydroponic growing equipment could be perfect for a Kratky set-up.
I looked at the Botanicare lidded 20 gallon hydroponics reservoir and sure enough it was BPA free, safe for food use. It just needed to be set up. The plastic on the reservoir lid is fairly rigid, and it needed support and special care when drilling holes in it so as not to crack. I got a 3” circular drill bit that matched the 3” net cups I wanted to use. Placing the lid on a piece of plywood I started to drill holes in the lid, the torque of the drill almost ripped my arm off as well as sending the lid flying across the room. I found that running the drill backwards created a much smoother, slower cut that wouldn’t crack the plastic or rip my arm off.
After drilling 15 holes in the lid and testing to see that the net cups were the right size to fit exactly into the holes, I was ready to fill the reservoir with filtered water and place my 15 lettuce seedlings in the cups. The lettuce seedlings had been germinated in starter plugs inside a Nanodome a few weeks earlier. As soon as they were showing roots out the bottom of the plug, they were ready to be transferred to my Kratky system.
I added a ½ dose of Foxfarm Grow Big nutrient for hydroponics to the Kratky reservoir and made sure the bottom of the net cups and plugs were just barely touching the water. I filled the net cups with Hydroton and nestled the starter plugs down into them to keep the seedlings stable and to discourage algae growth.
As the lettuces began to shoot their roots into the liquid, I added a bit more nutrient to bring it up to the full suggested dose. I fully expected to have to fuss with the pH level, but my whole system has stayed pH balanced, and my lettuces are huge, tasty, and crisp. I love this no-fuss system that has given me a massive yield of lettuces!
Drop by Fifth Season Gardening and we can help set you up with a Kratky system or any other hydroponics system to get you growing. At Fifth Season you will find everything you need for year-round indoor and outdoor gardening, including tips, recommendations, and advice.