I read some in a book that Brian got for me from the Round Rock Library, "Rodale's Vegetable Garden Problem Solver" (which by the way, is an awesome book), about planting seeds. It warned against planting seeds in potting soil, which has a lot of nutrients. Since the seed itself contains all of the nutrients it needs, the extra nutrients from the soil may overwhelm it, cause the inital sprout to shoot up high, and then it may fall over. Sounds like my lettuce! It recommends using a "sterile germination mix especially designed for seed-starting." Guess I'll have to do that for the spring!