I frequently hear from readers that their lettuce is too bitter, or that it is growing too tall, or that they have trouble getting iceberg lettuce to make big heads. It’s not surprising that people often ask about lettuce, since it is the second most popular vegetable for home gardens — after tomatoes.
The Romans and Egyptians grew a lot of lettuce; George Washington devoted almost a third of his huge Mt. Vernon garden to lettuce; and just about every ultra-modern urban rooftop greenhouse or fancy hydroponic operation grows lettuce. Even the experiments in growing plants in outer space stations use lettuce as a base crop.
The key to growing great lettuce is to make it grow really quickly. Young lettuce plants that have grown rapidly taste the best, while older lettuce that has struggled a bit tastes bitter and often grows tall and starts to flower. Rapid growth is also the key to growing nice iceberg lettuce. When I grow lettuce and if, for some reason, the plants aren’t growing quickly, I find it’s best to just throw them away and start over; waiting for struggling plants to turn around never seems to work out well. The same goes for plants affected by pests. If a problem develops, I never treat in hopes of saving a crop; I just start over.
Lettuce grows best in cool weather, so most folks grow lettuce in the spring and fall. Daytime temperatures below 75 degrees Fahrenheit with nights more than 40 degrees are ideal. This can be pushed a bit by starting the young plants inside before planting outside during spring and fall. Using other crops, such as corn, to shade the growing area can also benefit summer crops. One of my favorite tricks for fall crops is to cover the planting soil with thick mulch for the few weeks prior to planting in late summer; this can lower the soil temperature considerably. Of course, cold frames, hoop tunnels and shade cloth can also be used to stretch the growing season.
In general, I like to start lettuce seeds in a separate starting area, like my coldframe, and then transplant the little plants when they are a few inches high. If I do buy little plants at the nursery, I always look for the youngest and smallest plants, not the better looking and larger ones, because I think the bigger nursery plants are often stunted in the plastic containers. The scrawny little guys seem to have better momentum when planted in the garden.
Lettuce plants are fairly heavy feeders, so I try to enrich the soil with a lot of manure or other organic material before planting, and then I also feed frequently, usually once a week with a liquid fertilizer, such as manure tea (or a commercial product if I’m lazy). The idea is to push for maximum possible nutrient availability for the young plants.
Because lettuce is such a short-term crop, I often plant it in between long-term crops. I plant lettuce in between all the spring plantings of corn and squash and the fall plantings of broccoli and cabbage, and the lettuce is in and out before the main crop grows large. This clever arrangement is called catch-cropping, and it’s a great way to get more stuff growing in a small garden space.