Lettuce is a cool-weather vegetable, able to grow early in spring and into winter, depending on the variety. Lettuce growth is stunted during summer. Lettuce comes in leaf variety, cos or romaine, crisphead, butterhead and stem according to the University of Illinois. To extend the growing season, lettuce seed requires germination indoors before transplanting to a larger pot or into the garden. Seeding directly into the garden is the easiest method, however, and is relatively simple to do.
Prepare the soil by removing large stones or debris and mixing in three to four inches of organic material with a rototiller. Till the soil to a depth of six to eight inches.
Make rows using the edge of a hoe, spacing the rows 12 to 15 inches apart for leaf varieties and 24 inches for other varieties, says Ohio State University. Dig the rows to a depth of a 1/4 to 1/2 inch.
Place seeds into the rows at a rate of 10 seeds per foot covering the seeds with a 1/4 to 1/2 an inch of soil, says the University of Illinois Extension.
Water the area thoroughly, slowly to not wash the seeds away. Allow the seed five to 10 days for germination. Thin the seedlings so that they are four inches apart for leaf lettuce, and six to eight inches for other varieties.