I have grown hydroponic lettuce successfully and really enjoyed it, but that was all indoors, and while I found the lettuce acceptable, it was a not as crisp as I would like from not having the normal stresses of outdoor life to toughen the leaves up. I had a fan blowing over them once an hour, but that can only do so much.
I started a couple Reine des Glaces and Green Towers from seed outside in January and they did great, but got infested with countless hordes of aphids. I washed them off quite a bit, but you can only do so much at that point.
I wanted to find out how large organic operations managed to grow lettuce and control for aphids without sprays and after quite a bit of research I found this video.
I started my own Sweet Alyssum plants the next day. I have a standalone pot of it growing so I can move it around, and planted some below a couple tomatoes. According to the research that should be way more than necessary. I have one lettuce plant growing hydroponically outside at the moment and haven’t seen a single aphid on it in the last couple weeks. The plant definitely had a few aphids colonizing it when I started the Sweet Alyssum, so this is a good sign that it does work.
Now I have some lettuce starts nearly ready to transplant outside.
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.