Growing Lettuce in Southern California

Perform a soil test to determine the pH of the soil in your garden. Lettuce thrives in a soil with a pH range between 6.0 and 6.5. Depending on the test results, incorporate limestone in the soil to a depth of 7 inches to raise the pH, or work in sulfur to lower it. For exact amendment amounts for the size of your plot, use instructions provided with the soil pH testing kit or consult your local Cooperative Extension Service.

Cultivate the soil in a sunny part of the garden to a depth of 6 inches. Work in a layer of compost and a 5-10-10 fertilizer to improve drainage and nutrients. Aim for soil that's loose and easily falls between your fingers.

Sprinkle the seeds in rows that are spaced at least 12 inches apart. Sow at a rate of 10 seeds per foot, and lightly cover the seeds with a half an inch of soil.

Water the soil carefully to make sure you don't wash away the seeds. Keep the soil moist -- not wet -- throughout the germination and growing period. Depending on the type of lettuce you're growing, expect germination to set in within three to seven days.

Determine what the average size is for a fully grown crop of the lettuce you're growing. Thin the seedlings to accommodate this size. Inches can range from 4 to 6 inches and 10 to 12 inches depending on the type of lettuce you grow.

Spread organic mulch around your lettuce to maintain a cool soil temperature, promote soil moisture retention and to combat weeds.

Harvest the crops when they're fully grown. Remove the outer leaves, or cut them down to the crown so that the roots can grow new crops.