Lettuce (Lactuca sativa) is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. In many countries, it is typically eaten cold and raw, in salads, hamburgers, tacos, and many other dishes. In some places, including China, lettuce is typically eaten cooked and use of the stem is as important as use of the leaf. Both the English name and the Latin name of the genus are ultimately derived from lac, the Latin word for “milk”, referring to the plant's milky juice. Mild in flavour, it has been described over the centuries as a cooling counterbalance to other ingredients in a salad.Grigson, p. 313 In his humorous essay 100 Things I Hate, filmmaker John Waters refers to iceberg lettuce as "the polyester of greens".

Description

The lettuce plant has a short stem initially (a rosette growth habit), but when it blooms the stem lengthens and branches, and it produces many flower heads that look like those of dandelions, but smaller. This is called bolting. When grown to eat, lettuce is harvested before it bolts. Lettuce is used as a food plant by the larvae of some Lepidoptera. The largest lettuce head, of the Salad Bowl cultivar, weighed 11 kg (25 lb) grown by Colin Bowcock of Willaston, England, in 1974.

Cultivation

Lettuce is grown commercially worldwide. Hardy to Zone 6. Light, sandy, humus rich, moist soil. Dislikes dry conditions and can cause plants to bolt (go to seed). Early and late sowing in sunny positions or summer crops in shade . It is considered fairly easy to grow and a suitable crop for beginners.

Planting Depth: Some resources suggest planting seeds by covering lightly with soil while others suggest a depth of 1/4 to 1/2 inch

Planting Spacing: Thin seedlings to 10 cm (4 in) apart for leaf lettuce sq. m (9/sq ft) and 6 to 8 inches apart for Cos or Butterhead (4/sq ft - 1/sq ft), transplant Crisphead seedlings 10 to 12 inches apart in the row (1/sq ft).

Row Spacing: 12 - 18 inches apart

History

The earliest depiction of lettuce is in the carvings at the temple of Senusret I at Karnak, where he offers milk to the god Min, to whom the lettuces was sacred. Later, Ancient Greek physicians believed lettuce could act as a sleep-inducing agent. The Romans cultivated it, and it eventually made its way to France cultivated of the Papal Court at Avignon.Grigson, p. 312 Christopher Columbus introduced lettuce to the new world.

Cultivars

There are six commonly recognised Cultivar Groups of lettuce which are ordered here by head formation and leaf structure; there are hundreds of cultivars of lettuce selected for leaf shape and colour, as well as extended field and shelf life, within each of these Cultivar Groups: