Most of Ontario grown field lettuce types include:
A limited amount of lettuce is produced in greenhouses year round. Ostinata and Carlos are two varieties specific for greenhouses.
Lettuce is low in calories, and a source of Vitamin A, Vitamin C and folacin.
As a general rule of thumb, darker green lettuce varieties contain the most Vitamin A.
Lettuce was eaten by the ancient kings of Persia (that makes it about 2,500 years old).
The Romans seemed to have been the first to use lettuce in salads. The main variety they enjoyed we still know today as Romaine.
The 17th century horticulturist, John Evelyn, introduced the vegetable to England, but it was not until the present century that lettuce became popular in North America.