I am really happy I started growing lettuce with the Kratky method. I really like good, clean lettuce. You just can’t get it from a store anymore. What you can get from a store is “triple washed”, bruised, sad looking, sometimes decaying leaves. No matter how hard I examine a bag or container in the store, I don’t see the carnage until I pour it out.
Now that I’ve grown some full size lettuce, I’m going to scale back the amount of solution I use to 1.5-2 liters, down from 4. They might need 4 if they’re grown outside with windier or warmer conditions, but indoors they don’t drink much.
Now that there are longer days, the lettuce is growing faster. Gaviota grew out to a full size from seed in 40 days. Gaviota is an awesome lettuce. It grows loose and bushy, with slightly curled leaves. You can cut it at the base, and all the individual leaves are all separated at once. The slightly ruffled leaves make for a light and fluffy salad. It grew awesome with hydroponics. I don’t think this will work well for periodic harvesting.
Red Sails is a pretty leaf. It also grew awesome with hydroponics. The leaf size is huge so you have to tear it down for a salad. It is a little slower to grow, I’m letting it go for another 10-14 days for 50-54 total.
Three months ago I first posted about doing Kratky on a small scale of one container per plant. A short time afterwards I got a whitefly infestation in my indoor garden, and had to cut everything down. It was a shame, since the lettuce plants were just starting to get big.
It’s been six weeks now since I started new plants from seed, and I am trying four different varieties to see which grow better with this method.
Harmony MTO lives up to the reputation of bib lettuce varieties doing the best in hydroponics. Almost nearly as good, the Multigreen 3 MTO is getting quite big now. Buttercrunch and Green Towers look okay, but are slow growers. These varieties are 60-68 days to maturity, but they have been growing in winter light, so I’m giving them a few more weeks than that.
With Kratky, the plant should consume all the liquid provided to it and be ready to harvest when it is gone. Harmony has used a liter, during an estimated half of its lifespan, while Green Towers has barely used any. It will be interesting to see if Harmony can actually consume all that water before I am ready to harvest.
I will be starting 4 new varieties of lettuce in a few weeks so they will be ready to be transferred in after these are harvested.
March 2015 Update: I have started to “cut and come again” these lettuces. Altogether they make a great mix. The Harmony is a huge leaf, so I tear those up, they are neutral flavor. Multigreen is a nice frise style that is slightly bitter. Buttercrunch is quite nice, though nothing special. Green Towers is nice and crisp – I’m going to grow 3 of these to a container next time. If I had more room, I would probably rotate 3-4 of these in every 3-4 weeks or so to have a regular supply.
I tried to grow lettuce in soil in my indoor garden once, and failed miserably. I haven’t tried again since. It seemed a waste to dedicate a full pot for such little return, and it was easier to buy. Bulkier greens like Swiss Chard are an exception as they are great for continuous harvest, and do great in the pots.
I have previously made and used an ebb and flow hydroponic system and grown many tomatoes, and herbs. It worked great, but took some work to maintain the solution, keep the aerators clean, the pump working, and was only good for a larger scale operation. I’ve since moved into a smaller space, and have tried to keep accumulations of stuff to a minimum, so I definitely didn’t want to go that route again.
I discovered the Kratky method for lettuce production and decided to give that a go. There are no air or water pumps, no circulation, and all the solution you mix is consumed by the plant. The water level starts at the base of the net cups and as the plant absorbs the solution, the roots grow down into it, exposing the growing roots to more air. When the solution is gone, either the plant is ideally mature enough for a full harvest, or you add some more solution if you are doing a continuous harvest.
I went to Daiso in search of appropriate sized containers to act as the reservoirs. Daiso is a great Japanese store that I’m lucky to have in my area. Odds are you can find exactly what you want there or something that will work for your project. I managed to find an opaque CD/DVD container that holds 4 liters, and purchased four of those. Doing individual containers will allow me to stagger the growth while maintaining optimal levels of solution for each set of plants. Ideally there will be one lettuce plant per 4 liter container. If you have multiple lettuce seeds germinate in a container thin it out to a single plant. I’ve grown multiple plants in a container and they don’t produce as well as a single plant – too much competition for space & resources.
The container prep is really simple, just drill a hole into the lid of your container at the appropriate place.
To start the plants, soak a Rapid Rooter until it is moist enough so that when you gently squeeze it, drops form on the surface, but don’t create a torrent of water. Then place individual seeds in a Rapid Rooter and put it into a humidity dome until it germinates. After a couple days post-germination, put the Rapid Rooter into a net cup and drop that into the reservoir. Make sure that 1/8″ to 1/4″ of the net cup is covered by the solution, if not, add more.
I have broken down the formulas of each nutrient below. To mix, I pour each element, one at a time, into a container to weigh it, and then pour it into the mixing container. That way I don’t accidentally add too much of one thing into the mix since you can’t take it out once you put it in.
I am mixing them into a total of 1 liter of concentrate solution (using the 16 liter formula), for easy mixing and measuring – each 4 liter container will get 250ml of solution. Then I pour out the measured solution into the reservoir and fill it up the rest of the way with water and mix it up.