Care of Iceberg Lettuce

Remove weeds from the lettuce bed. Iceberg lettuce has shallow roots and can't compete with other plants for moisture and nutrients. During the season, weed frequently but carefully to avoid disturbing the iceberg's roots.

Prepare the soil by adding 2 to 3 inches of sand – unless you have sandy soil – and 3 pounds of 5-10-10 fertilizer for each 100 square feet of lettuce bed. Combine these ingredients into the top 6-inch layer of soil, water that layer and then rake until smooth.

Plant the iceberg lettuce seeds 1/4 inch deep, an inch apart in rows that are 18 inches apart. Keep the bed moist at all times during germination. This should occur within one to three weeks.

Thin the iceberg lettuce seedlings to 12 inches apart when they reach 2 inches high.

Irrigate the lettuce bed often enough to keep it slightly moist. Too much water causes bottom rot but, since iceberg lettuce is 90 percent water, it requires an ample supply to grow. The most critical time to supply water is in the 30 days leading up to harvest. Never allow the top 6 inches of soil to dry during this time.

Fertilize the iceberg lettuce with ammonium nitrate 30 days after planting. Use the rate recommended on the package. Dig a trench, 2 inches deep and 2 inches away from each row of lettuce. Spread the ammonium nitrate along the bottom of the trench, fill it up with soil and water to a depth of 6 inches. This method of fertilizing is known as sidedressing, and it avoids burning the plant's roots with the fertilizer.