Reply #9: Re:

[Ringo84]

Climatic Requirements

Lettuce is a cool-season vegetable and develops best quality when grown under cool, moist conditions. Lettuce seedlings will tolerate a light frost. Temperatures between 45 F and 65 F are ideal. Such conditions usually prevail in Ohio in spring and fall. Seeds of leaf lettuce are usually planted in the spring as soon as the ground can be worked. Butterhead and romaine can be grown from either seeds or transplants. Due to its long-growing season, crisphead lettuce is grown from transplants. Transplants may be purchased or started indoors about six weeks before the preferred planting date.
Soil Requirements

Lettuce can be grown under a wide range of soils. Loose, fertile, sandy loam soils, well-supplied with organic matter are best. The soil should be well-drained, moist, but not soggy. Heavy soils can be modified with well-rotted manure, compost, or by growing a cover crop. Like most other garden vegetables, lettuce prefers a slightly acidic pH of 6.0 to 6.5.
Cultural Practices

Since lettuce seed is very small, a well-prepared seedbed is essential. Large clods will not allow proper seed-to-soil contact, reducing germination. Lettuce does not have an extensive root system so an adequate supply of moisture and nutrients is also necessary for proper development.

Fertilizer and lime recommendations should be based on the results of a soil test. Contact your local Cooperative Extension office for information on soil testing. As a general rule, however, apply and work into the soil three to four pounds of 5-10-10 fertilizer per 100 square feet of garden area.

Seed may be sown in single rows or broadcast for wide row planting. Wide rows should be 12 to 15 inches across. Cover the seeds with 1/4 to 1/2 inch of soil. Water carefully but thoroughly. Several successive plantings of leaf lettuce will provide a more continuous harvest throughout the growing season. Leave 18 inches between the rows for leaf lettuce, and 24 inches for the other types. To achieve proper spacing of plants, thinning of lettuce seedlings is usually necessary. Thin plants of leaf lettuce four to six inches or more between plants depending on plant size. Butterhead and romaine should be thinned six to ten inches between plants. Finally, crisphead transplants should be spaced 10 to 12 inches apart in the row.

An organic mulch will help conserve moisture, suppress weeds, and keep soil temperatures cool. If weeds do become a problem, either pull by hand or cultivate very shallowly to avoid damage to lettuce roots. Planning your garden so that lettuce will be in the shade of taller plants, such as tomatoes or sweet corn, in the heat of the summer, may reduce bolting.

Insect pests and diseases can occasionally cause problems on lettuce. For proper identification and control recommendation, contact your local Cooperative Extension office.
Harvesting

All lettuce types should be harvested when full size but young and tender. Over-mature lettuce is bitter and woody. Leaf lettuce is harvested by removing individual outer leaves so that the center leaves can continue to grow. Butterhead or romaine types can be harvested by removing the outer leaves, digging up the whole plant or cutting the plant about an inch above the soil surface. A second harvest is often possible this way. Crisphead lettuce is picked when the center is firm.

The author gratefully acknowledges James D. Utzinger, on whose original fact sheet this is based.
Ringo