Plant lettuce seeds 2 to 3 weeks before last frost date for your area. Fill the container with soil to one inch below the rim. Make one row down the middle of the container and a row 3 inches away on each side of the middle row for a total of 3 rows in the container. Make your rows ½ inch deep. Thinly sprinkle the seed in each row using your thumb and index finger. Seed this way for all lettuces. Cover with soil. If you do not plant seeds on top of one another, you will not have to thin the lettuce.
Be sure to harvest regularly once the lettuce is about 4 inches tall. You may harvest by gathering the outer leaves as they grow by pinching them about 1 inch above the soil. Be careful not to pull any of the roots out of the soil or damage the growing point, which is at the center of the plant. You can also cut some or the entire plant with a scissors about an inch above the soil when the leaf is long enough, or you can cut the entire plant when the leaves are 4 to 5 inches in length. It is very important to wash the lettuce under cold water immediately, spin or shake out the excess water in a colander and store in the refrigerator after harvesting. This gets the field heat out of the lettuce and it will stay fresh much longer.
Once you see a thick stem in the middle, this means the plant has bolted and the leaves will taste bitter. (Bolting refers to the process where a mature plant begins to form seeds. At this point, the plant is tougher and may be bitter). You can get 2 to 3 harvests from one plant by handpicking or cutting outer leaves about one inch above the soil with scissors.
Lettuce grows best in cool weather so start this vegetable early. In very warm climates, you may want a put a shade cloth over the south face of lettuces and spinach during mid day using a couple of short bamboo stakes for support. You can also move to partially shaded areas. Lettuces will grow well in areas where you do not have full sun.
There are different maturities for different types of lettuces. Follow these directions for all varieties of lettuce.
Tip for growing more lettuce!! After 45 to 60 days your first planting of lettuce will have bolted and it is time to remove the plant and the roots. Use your spade to turn the soil over and add new soil as needed to one inch below the rim of the container. We suggest adding at least 25% new soil. You are now ready for the second planting in the container. This is called succession planting and works well for vegetables such as lettuce that mature very quickly. Do not plant your second planting in the warmest part of the summer as lettuce is a cool weather crop and will not germinate if the temperatures are too warm. In Duluth, I wait until the first week in August to start the second planting. Farther south you can start this in the fall.