Lettuce (Lactuca sativa) is an annual plant of the daisy family and is most often grown for its leaves, but sometimes for its stem and seeds. Lettuce is easily cultivated, although it requires relatively low temperatures to prevent it from flowering quickly. Lettuce is most often used for salads, although it is also seen in other kinds of food, such as soups, sandwiches and wraps
Lettuce was first cultivated by the ancient Egyptians who turned it from a weed, whose seeds were used to produce oil, into a food plant grown for its succulent leaves and oil-rich seeds. Lettuce growing spread to the Greeks and Romans and by 50 AD there were multiple types, often described in medieval medicinal writings. Many varieties were developed in Europe and by the mid-18th century many cultivars were described. Europe and North America originally dominated the market for Lettuce, but by the late 1900’s consumption of Lettuce had spread throughout the world.
Lettuce leaves are mainly green, but there are now varieties in red, gold and even blue-teal. They have a wide range of shapes and textures, from the dense heads of the iceberg type to the notched, scalloped, frilly or ruffly leaves. Depending on the variety and time of year, Lettuce is generally harvested at 65–130 days. Due to its short life span, after harvest lettuce was originally sold relatively close to where it was grown, but the early 1900’s saw the development of new packing, storage and shipping technologies that improved the lifespan and transport which resulted in a significant increase in availability. Fields of Lettuce is a common sight now in our area, most of which is sent back to the UK and Northern Europe.
Cultivars
There are several types of Lettuce, but three (leaf, head and cos or romaine) are the most common:
Leaf – Also known as looseleaf, cutting or bunching Lettuce, this type has loosely bunched leaves and is the most widely planted. It is used mainly for salads.
Romaine/Cos – Used mainly for salads and sandwiches, this type forms long, upright heads. This is the most common Lettuce in Caesar salads. Iceberg/Crisphead – This is very heat-sensitive and was originally adapted for growth in the northern US. It ships well, but is low in flavour and nutritional content, being composed of more water than most lettuce. Butterhead – Also known as Boston or Bibb, this type is a head Lettuce with a loose arrangement of leaves, known for its sweet flavor and tender texture.
Summercrisp – Also called Batavian or French Crisp, this Lettuce is midway between the crisphead and leaf types and tend to be larger, bolt-resistant and well-flavoured.
Woju – A Lettuce variety grown for its stem used in Chinese cooking.
Many insects are attracted to Lettuce including cutworms, which cut seedlings off at the soil line and aphids, which cause yellow, distorted leaves. Lettuce also suffers from several viral and fungal diseases which can cause entire plants to rot and collapse.
In addition to its usual purpose as an edible leafy vegetable, Lettuce has had a number of uses as a medicinal herb and religious symbol. Ancient Egyptians and Romans thought Lettuce was a symbol of sexual prowess and a promoter of love and childbearing in women, while the ancient Greeks connected Lettuce with male impotency and served it during funerals. Some American settlers claimed that smallpox could be prevented through the ingestion of Lettuce and Iranian believed consumption of Lettuce seeds helped cure typhoid.