Lettuce (Lactuca sativa) is one of the most popular and widely consumed vegetables today, as well as historically. The Greeks, Persians, Romans, Egyptians, and Chinese considered lettuce a leafy delicacy and grew seeds for oil. Columbus brought lettuce and seeds on his voyage to the New World, as did most European explorers in their colonization efforts, rooting lettuce in America and most countries around the world. In the United States, the average person eats more than 25 pounds of lettuce each year.
Derived from wild, stemmy varieties, lettuce was cultivated over the centuries into what today are firmer heads with more leaves. Cultivation and breeding over the years has honed in on best features, including leaf shape, flavor, and resistance to disease and bolting. Newer hybrid strains have been bred to resist brown blight and mildew.
Iceberg lettuce, also called roundhead or crisphead, got its name in the early 1900s as it was shipped and stored in ice-filled containers. Romaine is so named because of its popularity in early Rome. Mesclun is not a variety itself, but a salad mix of baby lettuce and other greens including radicchio, arugula, mustard greens, and others.
References: Texas A&M AgriLife Extension Service, University of Arizona Cooperative Extension, University of Illinois Extension.
TYPES, VARIETIES & CUTS
Lettuce comes in four main varieties: leaf lettuce, including red and green varieties, where the thinner leaves and loose heads can range in taste from delicate to slightly bitter; butter lettuce including both Bibb and Boston, which is a sweeter variety when grown in cooler weather; romaine or cos, popular in Caesar salads, has dark leaves and a firm and crunchy leaf rib; and crisphead or iceberg has tightly packed leaves with a higher water content.
References: University of Maryland Extension, Clemson University Cooperative Extension, University of Arizona Cooperative Extension.
PESTS & DISEASE
Lettuce is susceptible to several pests and diseases including aphids, caterpillars, slugs, armyworms, imported cabbageworms, cabbage loopers, leafhoppers, leaf miners, lygus bugs, and thrips. Pests are more challenging to summer and fall crops than spring crops.
Seedlings are susceptible to damping-off; mature plants can be at risk for sclerotinia, mildew, grey mold, and Rhizoctonia bottom rot. Chemical controls are available for both pests and diseases. Bacillus thuringiensis is a nonchemical alternative to control caterpillars. Tipburn in mature plants can occur from changes in temperature or soil moisture. Too much heat or moisture can lead to rot.
References: University of California Cooperative Extension, University of Arizona Cooperative Extension, NC State University Cooperative Extension, Clemson University Cooperative Extension.