Lettuce

Guide Note:Lettuce is a leaf vegetable typically eaten raw on sandwiches, in salads and many other North American dishes, but is commonly cooked before being eaten in Asia.

An annual or biennial member of the Asteraceae (daisy) family, lettuce grows best in temperate climates and is harvested before it flowers when grown for food. Six major groups of lettuce are cultivated for human consumption: Chinese, butter head, crisp head (iceberg), looseleaf, summer crisp and romaine.

Lettuce is believed to have originated in the Mediterranean region and can be seen in Egyptian tomb paintings dated to 4500 B.C. Christopher Columbus introduced lettuce to the new world, and wild varieties are now common in Europe, North America and temperate Asia. Fast Facts:

1. Romans ate lettuce after meals to induce sleep
2. 95% of all lettuce in US grown in California and Arizona
3. Largest known head weighed 25 lbs
4. Valuable source of vitamin A and folic acid
5. Lactucarium ("Lettuce Opium") is a substance resembling opium present in all lettuce