Lettuces are a year-round salad crop that are well-suited to British gardens. They are divided into two broad types depending on their growth habit: heading lettuces and non-heading or ‘loose-leaved’ lettuces. The heading lettuces are then further divided into several types:
• Heading lettuces
Heading varieties have leaves that are packed together to form a head in the centre of the plant.
Cos/romaine. Elongated, upright leaves form loaf-like heads. In our experience, the taller types tend to produce loose, open heads, while the smaller framed cos types form heads that are firm and dense. These smaller types are often called ‘Little Gem’, though originally the term ‘Little Gem’ referred to a specific variety. The texture is crisp and crunchy, and the plants, especially the small-framed cos varieties, mature quite quickly.
Crisphead. Produce large, firm and roundish heads made of crisp leaves that are blanched white in the middle. With their spreading outer leaves removed, these lettuces are sometimes sold as ‘icebergs’ in the shops and supermarkets.
Batavia. Generally refers to varieties that produce smaller, less dense heads than the crispheads, though some are non-heading. They have a reputation for their excellent flavour.
Butterhead. Leaves are thin and soft with an oily texture. The outer ones are prostrate and light green, while those in the centre form a small, loose head that is yellowish in the middle. Plants are quite quick to mature.
• Loose-leafed lettuces
These are non-heading varieties that can be harvested as a cut-and-come-again crop to extend the harvest period. Well-known types are the self explanatory oak leaf varieties and the broad-leafed lollo types whose leaves have frilly margins.
The range of colours in lettuces is quite limited, and most varieties come in some shade of light green. A minority, however, are pigmented red on the parts of the leaves exposed to sunlight, while the occasional variety is speckled with splotches of red.
Although, lettuces are generally considered to be a summer crop they are relatively cold tolerant and can be grown well into the autumn.
For growing over the winter months there are specific varieties that are adapted to grow under the low light conditions of the winter. To get the best results, though, even winter lettuces should be provided with protection, such as a cloche or in a greenhouse or polytunnel, from the worst winter weather.