2. Sow lettuce seeds ¼-inch deep in rows spaced 12 to 18 inches apart. Thick seeding (about a tablespoon of seeds per 10-foot row) results in plenty of thinnings to eat as the lettuces grow. Keep the soil moist until the seeds germinate.
3. Once the plants have grown two to four true leaves, thin seedlings to four inches apart. Thin again when the seedlings begin to touch shoulders. For heading types, the final spacing should be at least a foot; lettuce will not form a head if crowded.
4. Grow lettuce in the cooler months, or plant it in the shade of taller crops. Heat causes lettuce to turn bitter and leathery.
5. Keep lettuces hydrated. When rain is insufficient, provide one to two inches of water per week. Plants in pots dry out more quickly than those in the ground.
6. Plant successive crops. A series of small plantings, every two to three weeks, ensures a steady supply of salad greens.
7. Extend the season. Start plants indoors under grow lights, five to six weeks before the last frost date. Use row covers to protect fall-planted lettuces into early winter.
8. Rotate crops. Growing lettuce in the same spot each year depletes the soil and eventually results in weak growth.