With the exception of the iceberg variety, lettuce is also a good source (10–19% DV) of folate and iron (table). "Lettuce" is synonymous with "salad" for people all over the world. Lettuce can be grown from seed or from steams depending on the variety. By the late 20th century, the preferred types began to change, with crisphead, especially iceberg, lettuce becoming the dominant type in northern Europe and Great Britain and more popular in western Europe. In 2013, 24.9 million tons of lettuce were produced in the world. Lettuce grown on the International Space Station has been served with tacos and cheeseburgers, and it turns out to be just as nutritious as the Earth-grown version , Western Europe and North America were the original major markets for large-scale lettuce production. Romaine lettuce is often used for Caesar salads. Lettuce can be grown in a garden almost anywhere in the US, but by far the majority of commercial lettuce is grown in the Salinas Valley on California's central coast. Lettuce can be grown in a garden almost anywhere in the US, but by far the majority of commercial lettuce is grown in the Salinas Valley on California's central coast. However, in China, a majority of the lettuce produced is utilized for domestic consumption. Where (in the World!) Lettuce is a cool-season crop that grows best with moderate daytime temperatures (73oF) and cool nights (45oF). Imports from Spain and Northern Europe dominate the Italian market. Temperatures above 27 °C (81 °F) will generally result in poor or non-existent germination of lettuce seeds. Fungal diseases include powdery mildew and downy mildew, which cause leaves to mold and die and bottom rot, lettuce drop and gray mold, which cause entire plants to rot and collapse. The original stem type traveled eastward, ... produce nearly all the commercially grown lettuce in the world. The cultivated lettuce Lactuca sativa is a popular salad vegetable and is grown on all continents throughout the world including Australia.. Planting lettuce in a greenhouse  Salmonella bacteria, including the uncommon Salmonella braenderup type, have also caused outbreaks traced to contaminated lettuce. So, light but consistent watering is key. QUESTION: What lettuce grows well in summer? -Kelly W. ANSWER: By planting a few seeds every two weeks or so, gardeners in many parts of the world can grow lettuce year round.Most varieties of salad greens really thrive in the cool and mild times of year, when temperatures are 60 degrees Fahrenheit or lower. It is also stouter, the stem and leaves are more purple flushed, [disputed – discuss] the leaves are less divided, but more spreading. protect from slugs and snails. It has become naturalized in Europe because of its use as a vegetable. Certain varieties contain more than others, and some selective breeding and genetic modification studies have focused on using this trait to identify and produce commercial varieties with increased pest resistance. In the US, several varieties of lettuce are grown.  Many insects are attracted to lettuce, including cutworms, which cut seedlings off at the soil line; wireworms and nematodes, which cause yellow, stunted plants; tarnished plant bugs and aphids, which cause yellow, distorted leaves; leafhoppers, which cause stunted growth and pale leaves; thrips, which turn leaves gray-green or silver; leafminers, which create tunnels within the leaves; flea beetles, which cut small holes in leaves and caterpillars, slugs and snails, which cut large holes in leaves. Lettuce grows best in full sun in loose, nitrogen-rich soils with a pH of between 6.0 and 6.8.  Weeds can also be an issue, as cultivated lettuce is generally not competitive with them, especially when directly seeded into the ground. However, in China, a majority of the lettuce produced is utilized for domestic consumption. An explanation of the special requirements for container crops.Best growing conditions of lettuce.A step by step guide to growing lettuce in pots. , Lettuce appears in many medieval writings, especially as a medicinal herb. How to Keep Growing Lettuce in Fall (and Winter) Even in cold winter areas, you can grow lettuce through the colder months if you give your plants some protection. Lettuce is easy to grow. The FDA and the Centers for Disease Control and Prevention on Tuesday said romaine lettuce grown in Florida is safe to eat. They need moist soil to grow correctly.  The ovaries form compressed, obovate (teardrop-shaped) dry fruits that do not open at maturity, measuring 3 to 4 mm long. , Soil nutrient deficiencies can cause a variety of plant problems that range from malformed plants to a lack of head growth. Books published in the mid-18th and early 19th centuries describe several varieties found in gardens today.  The current word lettuce, originally from Middle English, came from the Old French letues or laitues, which derived from the Roman name. In addition, since the temperature, humidity, carbon dioxide, lighting, and other conditions can be perfectly controlled by ICT, a stable yield of high-quality, low-potassium lettuce can be harvested throughout the year. The cultivated variety appears to have been about 75 cm (30 in) tall and resembled a large version of the modern romaine lettuce. , Other bacteria found on lettuce include Aeromonas species, which have not been linked to any outbreaks; Campylobacter species, which cause campylobacteriosis; and Yersinia intermedia and Yersinia kristensenii (species of Yersinia), which have been found mainly in lettuce.  In spite of its high water content, traditionally grown lettuce has a low water footprint, with 237 liters of water required for each kilogram of lettuce produced. In warm climates lettuce growing is usually restricted to the spring and fall, when temperatures are more moderate than in summer or winter. Heat generally prompts lettuce to bolt, with most varieties growing poorly above 24 °C (75 °F); cool temperatures prompt better performance, with 16 to 18 °C (61 to 64 °F) being preferred and as low as 7 °C (45 °F) being tolerated. This Primefact includes information on: Lettuce is the only member of the genus Lactuca to be grown commercially. Although this trait can be a problem to home gardeners who attempt to save seeds, biologists have used it to broaden the gene pool of cultivated lettuce varieties. This large price difference is justified; as hydroponic lettuce has a better taste, is grown without pesticides, and requires significantly less water to grow. Where did lettuce originate from? This lettuce is so local, they grow it right in the supermarket QFC supermarkets around Seattle now feature standing indoor farms that grow the produce in the store. Ancient records note that lettuce was served at the royal table of Persian kings as early as 550 B.C. By 50 AD, many types were described, and lettuce appeared often in medieval writings, including several herbals. Originally, the countries of North America and Western Europe ranked the highest in lettuce production in the world. The salad crops were free of disease and even more nutritious than ones grown on Earth. Spacing of about 6 to 18 inches between romaine lettuce plants to ensure they get enough nutrients and space to grow. So, with the hot months approaching, now is a good time to discuss growing this vegetable.. Lettuce spread to the Greeks and Romans; the latter gave it the name lactuca, from which the English lettuce is derived.