do you think it might be a lack of light?

I am no lettuce expert but low light levels could explain the problem with the tomato plant and cucumbers.

puffysmom ,

I grow lettuce indoors in hydroponic set-up under fluorescent lights. I keep the lights on 16-18 hours a day and the plants grow great!! I would suggest going to your local book-store (or library) and reviewing a book on greenhouse gardening of lettuce just to see what they suggest. I usually go to Barnes and Noble grab a cup of coffee and take 5-6 books to the table with me and do my research. I could go check the books out of the library but the ability to enjoy a cup of coffee or tea while I do research appeals to me. Also you will only get the latest books in a book store with the most up to date info - IMHO. Depends on what the quality of your local library is as to how up to date their books on greenhouse gardening are. You can also call bookstore and/or library before you go just to find out IF they have books you might want to review.

NO can do?? Then GOOGLE greenhouse growing of the veggies you want to greenhouse grow and see what comes up.

Good Luck!!

DL

I have better luck with lettuce by planting them in those long planter boxes like you'd use on the patio with promix or a good potting soil mix. Lettuce is a fairly heavy feeder but too much feed will cause tipburn on the edges of the leaves. I use a 20-20-20 constant feed at 100 ppm. Watch for aphids. It also grows well in a hanging basket.