Lettuce

Lettuce has been cultivated and selectively bred for several centuries, first in the Middle East, then by the Romans who named it “latuca” or milk because of its white sap. The name became lettuce in English. Few vegetables are as easy to grow year-round with such a multitude of varieties.

Leaf Types

• Crispheads, widely available in markets as fresh produce, are not at all heat resistant and tend to bolt in hot weather. Some gardeners find crisp heads difficult to grow.
• Butterhead or bibb lettuce is smaller growing with looser leaves than crisphead types.
• Romain, or cos, forms taller, upright heads with crisp, wavy leaves; some form fairly tight heads.
• Loose leaf types come in shades of green or red, sometimes variegated, with leaves in many shapes. They are fast-growing and store well.
• A combination of lettuce types and leaf colors enhance the beauty of the vegetable garden as well as the gardener’s cuisine. 

Lettuce Hints

• Choose from among dozens, if not hundreds, of named varieties, some suitable as edgings in ornamental gardens. Mail-order nurseries carry a wide seed selection of named cultivars.
• Plant crisp head varieties in early spring only; they do not tolerate heat.
• Focus on growing lettuce only during the spring and fall-winter cool seasons in hot inland microclimates; provide shade if you attempt to grow lettuce in summer.
• Interplant long-season lettuce varieties that benefit from shade as the season progresses with tall summer crops such as beans, corn and tomatoes.
• Make successive plantings or plant varieties that mature at different times in mild microclimates to maintain a long season of harvest.

Sowing and Growing

• Provide warm conditions indoors, in a greenhouse, or under a cold frame to germinate lettuce. Seedlings can be planted outdoors after 3-4 weeks. Germination is best at 60-80 degrees.
• Direct sow seeds in loose, fertile soil, 1-2 in. apart. Amend heavy or clay soil with organic matter.
• Do not bury seeds but cover lightly with a dusting of soil; some light is needed for germination.
• Plan to transplant crowded seedlings. Space crispheads 12 in. apart in rows 12-18 in. apart. Space other types 6-8 in. apart to grow to maturity, closer in a cut-and-come-again regimen.
• Keep seeds and seedlings evenly moist to encourage rapid growth, but do not overwater.
• Time planting so lettuce matures during the cool season. It is extremely sensitive to high temperatures and dry conditions when it can become bitter and bolt (plants will flower and go to seed rapidly in high heat). Providing shade protects heads from short-term heat spells.
• Apply a 2-3 in. layer of mulch to prevent soil temperature from fluctuating, to retain moisture, keep soil off the leaves, and protect shallow roots.
• Cut entire heads or remove individual leaves to extend production without damaging the crown in the cut-and-come-again technique. New leaves grow after outer ones are harvested.
• Allow crisphead varieties to form large, firm heads before harvesting.
• Harvest early in the day for best quality and longer storage.
• Keep free of snails & slugs; spray aphids off with a moderate jet of water from a hose.

Additional Information

• Sonoma County Master Gardener Vegetable Planting Summary
• https://sonomamg.ucanr.edu/Food_Gardening_with_Less_Water/
• http://ipm.ucanr.edu/home-and-landscape/lettuce/index.html
• http://ipm.ucanr.edu/home-and-landscape/lettuce/cultural-tips/

February 2022