Lettuces are annual, low-growing, leaf vegetable plants, with green leaves, although some cultivars have red or reddish-green leaves. Lettuces are easy to grow, as they will grow even in containers and in very small gardens. They are cool-season crops, growing best at 10-20 Celsius degrees (50-68 F), some cultivars may tolerate some heat or frost. Cool nights are essential for good results. Germination is poor at temperatures above 25 Celsius degrees (77 F).
Lettuces vary in size from 10 cm to over 30 cm in spread, depending on the cultivar. They are mainly used in salads but may also be cooked or used in soups. There are several distinct types of lettuces: Cos - having long, substantial, well-flavored leaves with fairly loose hearts, Semi-cos - having shorter, very sweet, crunchy leaves, Butterhead - heaving smooth, soft leaves, forming a rounded, compact heart, Crispheads - heaving crispy leaves forming a heart, Loose-leaf - heaving leaves that do not form a heart.
Lettuces prefer an open site, or in light shade in very hot weather, with fertile, moisture-retentive soil and medium nitrogen levels. For a year-round supply, in cool climates you can sow lettuces from early spring to late summer, at 2-3 weeks intervals. At the end of summer or early autumn, sow hardy cultivars that will over winter outdoors or under cover for a spring crop.
Keep lettuce beds weed-free, apply a nitrogenous fertilizer or organic liquid feed if growth is slow. If the weather is dry, water the plants regularly. They are ready to harvest after 7-12 weeks after sowing, depending on the cultivar. They may be stored for a few days in the refrigerator.
