Growing Lettuce Year Round
Lettuce is generally considered a cool weather plant, grown in early spring or fall, although it can be grown in the warm season in most of the SF Bay Area by choosing varieties adapted to warmer weather. Check seed catalogs for summer lettuces.
Lettuce does best in a loose, well-drained soil, with regular watering and adequate nitrogen. Whether your soil is heavy clay or a light sandy type, the incorporation of compost will often improve the growing conditions. Homemade compost is ideal, with municipal compost made from green waste recycling being the next best. Dig thoroughly in 1-3" of compost with a shovel or spading fork to a depth of 6-8", shape the bed and level it. Just before planting, add a nitrogen fertilizer where the transplants will be planted according to fertilizer label recommendations. Good sources of organic nitrogen include alfalfa meal (my favorite), cottonseed meal, fish and/or kelp meal, as well as blood and feather meal. I have found the latter two attract dogs that try to eat the animal products, soil and all.
The best time to transplant is the late afternoon or on an overcast day. If transplanted in hot weather, the seedlings will need some shade protection for the first few days. To transplant, carefully remove each plant from its container by pushing the bottom of the six pack cells and lift small plants by the leaves. If the roots are at all matted, gently separate and spread them out. Set transplant slightly (1/2” or so) higher than the soil level into which it is being planted. Firmly press the soil around the rootball, making sure not to cover container soil with the garden soil but so they are nearly level with each other.
Water in thoroughly. Thoroughly means watering 2 – 3 times as long as you expect it should take, as water moves into and through soil much more slowly than you think. An application of liquid fertilizer may be helpful 1-2 weeks after transplanting, as the organic nitrogen may not become available for several weeks. Plant seedlings approximately 4-6" apart so that you may eat the thinnings at the point you thin to the final distance of 8”-10” apart.
Lettuce will be crisper if harvested in the early morning. Immediately after picking, wash thoroughly and get the excess moisture out. This can easily be done by placing freshly washed lettuce in a clean dish towel, hold cloth by four corners, going outside and fling in semi circle arc until water no longer flies off. Store in a plastic bag wrapped in the dishtowel to create a humid environment. Pick loose-leaf lettuce from the outside, letting the inner leaves continue to grow. Heading types such as romaine, Batavian and butterhead are usually pulled up whole, but these can also be picked outer leaves first until head begins to form.
Types and Varieties of Lettuces
There are several major types of lettuce which include: butterhead, cos (syn 'romaine'), loose-leaf, crisphead or icebergs and Batavian or summercrisp. Cos lettuce is very upright and columnar, forming a particularly sweet creamy white, crisp heart, surrounded by sturdy outer leaves. It is fairly demanding to grow in terms of being unforgiving of poor conditions and poorly adapted to hot weather. The crispheads are the slowest to bolt, then summercrisps, butterheads, leaf lettuces, and finally, cos types.