by National Gardening Association Editors
- Lettuce is a cool-weather crop. Sow seeds as soon as the ground can be worked in the spring and follow with small sowings at 10-to 14-day intervals until late spring in warm summer areas or early summer in the North.
- For earliest harvest, start seeds indoors 6 to 8 weeks before the last frost date and set them out after 3 weeks.
- Plant heat-resistant lettuce varieties for late spring sowings.
- Start fall crops in flats or directly in the garden in midsummer in northern states and in late summer in central and southern gardens.
- Work the earliest-drying part of the garden first for a spring crop.
- Add 1 pound of 10-10-10 or its equivalent per 25 square feet of growing area before planting in early spring.
- Sow seeds indoors 1/2 inch apart, 1/4 inch deep, in 4-inch-deep flats.
- Plant seeds outdoors in beds or rows 1/4 to 1/2 inch deep.
- Set out transplants spaced 3 to 4 inches apart for leaf lettuce, 6 to 8 inches for Cos and loose-headed types, and 12 to 16 inches for firm-headed types such as head lettuce.
- Sow in late spring in semi-shaded areas to extend the harvest into the summer.
- Thin seeded lettuce outdoors when plants are 2 inches tall to stand 3 to 4 inches apart for leaf lettuce, 6 to 8 inches for Cos and loose-headed, and 12 to 16 inches for firm-heading types.
- Mulch plants in early summer to keep the soil cool.
- Side-dress plants 3 to 4 weeks after planting; use 1 teaspoon 10-10-10 or its equivalent per plant or water with a mixture of fish and seaweed emulsion.
- Insects and diseases are rare in home lettuce plantings. However, see our article Summer's Bad Guys by Charlie Nardozzi for controls of common lettuce pests such as slugs, earwigs and whiteflies.
- Harvest leaf lettuce as soon as leaves are big enough to eat.
- For a steady harvest, cut heading types before they reach full size.
- Harvest in early morning when leaves are crisp and full of moisture.
Photography by Suzanne DeJohn/National Gardening Association
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