Lettuce is an annual leafy vegetable in the daisy family, domesticated from wild prickly lettuce (Lactuca serriola) near the Caucasus and pictured in ancient Egypt as early as 2680 BC. Iceberg lettuce, introduced in 1894, is still the most popular type in the United States. Most U.S. lettuce comes from California and Arizona.
Appearance
- Appearance
- A low rosette of green or red leaves, usually 6–12 in (15–30 cm) tall and wide. Cut stems and leaves ooze a milky sap, which gave the genus its Latin name from lac, "milk."
- Flowers
- When it goes to seed, a flower stalk shoots up to about 3 ft (1 m) and carries small yellow flower heads that look like little dandelions.
- Flowering time
- Hot weather makes lettuce , sending up its flower stalk. After bolting the leaves turn bitter.
- Fruit
- Each tiny dry fruit () holds one seed. Seeds can be white, yellow, gray, or brown, depending on the variety.
Look-alikes
Prickly lettuce has fine spines along the leaf veins and edges, grows in waste places and along roadsides, typically 2–4 ft (60–130 cm) tall and sometimes up to about 6 ft (2 m), and its upper leaves often twist to stand edge-up in the sun. Its pale yellow flowers are often tinged purple.
Why they get mixed upIt's the wild ancestor of garden lettuce, and it's a common weed of roadsides and fields in the U.S.
Where it lives
- Typical habitats
- farm fields
- vegetable gardens
- greenhouses
- Range
- Lettuce is a crop and doesn't grow wild on its own. From mid-November to early April, most U.S. lettuce comes from irrigated desert valleys in Imperial County, California, and around Yuma, Arizona. From late April to mid-November, production moves to Central California. About 85% of the lettuce Americans ate in 2022 was grown in the U.S.
- Preferred conditions
- It likes full sun and cool weather, ideally 61–64°F (16–18°C). Most varieties struggle above 75°F (24°C), and seeds sprout poorly above 81°F (27°C).
Life cycle
- Seed dispersal
- A feathery tuft () on each seed acts like a parachute in the wind.
Growing it
- Care
- Plant in loose, rich soil with a pH of 6.0–6.8. Most types are ready to harvest 65–130 days after planting. Rabbits, groundhogs, slugs, and aphids are common garden pests.
- Toxicity
- Because lettuce is eaten raw, it has been linked to many food-poisoning outbreaks, including E. coli O157:H7.
Name and classification
- Varieties and forms
- All salad lettuces are one species, sorted into groups: looseleaf (the most widely planted), romaine or cos, iceberg or crisphead, butterhead (Boston and Bibb), summercrisp (Batavian), celtuce or stem lettuce grown for its thick stalk, and oilseed lettuce grown for its seeds.
Conservation
- IUCN Red List
- NENot EvaluatedNot yet assessed
Culture and stories
- Culture and stories
- "Romaine" comes from the lettuce grown in the papal gardens of Rome, and "cos" from the Greek island of Kos.
- Romaine is the lettuce most often used in Caesar salad.
More species to explore
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