This is a half-hardy vegetable that you can keep growing all season long by planting one small crop at a time. Days to maturity tend to be short. Garden lettuce is far superior, in both taste and vitamin A content, to supermarket brands.
- Lettuce is a cool-season crop that grows well in the spring and fall in most areas. Lettuce seedlings will even tolerate a light frost. Temperatures between 45 F and 65 F are ideal.
- Loose, fertile, sandy loam soils, well-supplied with organic matter are best. Soil should be well-drained, moist, but not soggy with a slightly acidic pH of 6.0 to 6.5. Since the seed is so small, a well-tilled seedbed is essential. Large clods will reduce germination.
- Start seeds indoors 4 to 6 weeks before last spring frost date for earliest crop.
- One week before setting seeds or transplants in the ground, till in compost or organic matter, especially if you have heavy soils.
- Harden off seedlings for about one week, and transplant outside between 2 weeks before and 2 weeks after last spring frost.
- Direct sowing is recommended as soon as the ground can be worked. Plant seeds ½ inch deep. Snow won’t hurt them, but a desiccating cold wind will.
- Seed may be sown in single rows or broadcast for wide row planting. When broadcasting, you'll need to “thin” for the proper spacing.
- Leaf lettuce: Plant 4 inches apart.
- Cos and loose-headed types: Plant 8 inches apart.
- Firm-headed types: Plant 16 inches apart.
- Your rows of plants should be 12 to 15 inches across.
- Cover the seeds with ¼ to ½ inch of soil.
- Water thoroughly at time of transplant.
- Consider planting rows of chives or garlic between your lettuce to control aphids. They act as “barrier plants” for the lettuce.
- You should be able to sow additional seeds every two weeks for a continuous harvest throughout the growing season.
- Fertilize 3 weeks after transplanting. Lettuce prefers soil that is high in humus, with plenty of compost and a steady supply of nitrogen to keep if growing fast. Use organic alfalfa meal or a slow-release fertilizer.
- To plant a fall crop, create cool soil in August by moistening the ground and covering it with a bale of straw. A week later, the soil under the bale will be about 10 degrees F (6 degrees C) cooler than the rest of the garden. Sow a three foot row of lettuce seeds every couple of weeks—just rotate the straw bale around the garden.
- Make sure soil remains moist but is well-drained.
- An organic mulch will help conserve moisture, suppress weeds, and keep soil temperatures cool throughout the warmer months.
- Lettuce will tell you when it needs water. Just look at it. If the leaves are wilting, sprinkle them anytime—even in the heat of the day—to cool them off and slow down the transpiration rate.
- Weed by hand if necessary, but be careful of plant roots: They are shallow.
- 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.
- Lettuce should be harvested when full size, but just before maturity. You want it young and tender.
- Before maturity, you can harvest leaf lettuce by simply removing 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.
- Mature lettuce gets bitter and woody and it will go bad quickly, so check your garden everyday.
- As time passes, you will want to cut the whole plant from the ground.
- It’s best to harvest in the morning before leaves have been exposed to sun.
- Keep lettuce in the refrigerator for up to 10 days in a loose plastic bag.