Lettuce is a most poplar garden crop. Lettuce is easily grown and adds color and beauty to the home garden. One good reason for its popularity (aside from the fact that it tastes good!) is that lettuce is hardy and can be planted as early as the soil can be worked. So when you start getting the heebie jeebies because you have't had your fingers in the dirt for months, you can start lettuce as early as just about anything. It is a cool weather crop and makes its best growth at temperatures of 60-65°F (16-18°C). Careful variety selection is important for hot weather crops. Sow every 3 weeks for a continuous supply of fresh lettuce.
There are four types of lettuce. Crisphead types form heads and include the popular but nutritionally poor iceberg. Looseleaf lettuces like black seeded simpson and red salad bowl form loose heads. Butterhead types such as bibb or buttercrunch form small, tight heads with satiny leaves. And last, recently gaining great popularity, the romaines that form conical, upright heads are are probably the highest in nutrient content.
Lettuce is a cool season vegetable and will not tolerate hot, dry summer conditions. Plantings may be made starting April through early June and then again in late July - August for a fall crop. For a steady supply, succession planting can be made every 2-3 weeks during these periods.
When temperatures climb lettuce will tend to produce a seed stalk, also known as bolting. Bolting results in a bitter, unpalatable leaf flavor and should be avoided. Unless of course, you do this intentionally to save your own seeds.
Lettuce may be started indoors and transplanted or direct seeded. For transplants, start the seeds in pots filled with potting mix (available at most garden centers). Sow several seeds about a quarter of an inch deep and keep moist. After the seeds emerge thin so that the seedlings stand at least 2 inches apart. Full sun or grow lights should be used or else spindly, weak plants will result.
In about 4-6 weeks seedlings may be transplanted to the garden. For large heads space plants 10 inches apart. Place plants closer if you are harvesting for leaves only. Be sure to acclimate the plants to the outdoors first and transplant on a cloudy day or in the evening to prevent plant shock.
For direct seeding make shallow trenches and sow several seeds per inch, cover with a quarter of an inch of soil. Again, keep moist and when seedlings emerge thin so that seedlings stand at least 2 inches apart. You may gradually thin out the plants as they grow and eat the thinnings. This will provide a steady supply of tender baby leaves which are good in salads. For heads thin to 10 inches, for leaves leave plants closer together.
Lettuce maturity can be 3 or more weeks later in cool weather, and up to 1 week earlier in hot weather.
Thermal Dormancy: Lettuce can be dormant at high temperatures. For best germination results sow at soil temperatures of 68°F (20°C) or lower. The priming process in pelleted lettuce seeds broadens the temperature range in which the seeds will germinate, overcoming some of a lot's thermal dormancy.
Lettuce is relatively pest-free. In damp weather slugs can be a problem. Discourage slugs by cutting back on watering, avoiding the use of mulch and by spacing so that air can circulate around plants.
Harvest lettuce in the early morning and refrigerate immediately to preserve flavor and nutrients. Pick only as much as you will use in one day. Be adventurous and try some new lettuce varieties this year to spice up your salad life!