PREPARATION: Lettuce is hardy and can be planted as early as the soil can be worked. It is a cool weather crop and grows best at temperatures of 60-65°F. Careful variety selection is important for hot weather plantings. Sow every 3 weeks for a continuous supply of fresh lettuce.
GERMINATION: Lettuce seed can enter thermal dormancy when exposed to high temperatures. Do not use a heat mat when germinating lettuce seed. Optimum germination results at soil temperatures of 60–65°F.
TRANSPLANTING: Sow 2-3 seeds per cell, 1/4″ deep, 3-4 weeks before transplanting outdoors. Do not let soil above 70F while germinating so keep out of sun and a cool, dark location. Harden seedlings by reducing water and temperature for 2–3 days before planting outdoors. Properly hardened transplants can survive temperatures as low as 20°F. Transplant iceberg and romaine lettuce 10–12″ apart, in rows 18″ apart. Other types 8–10″ apart in rows 12–18″ apart for full size heads or 6″ apart for mini heads.
DIRECT SEEDING: Seeds germinate at low soil temperatures (40°F), but poorly above 75°F. Sow seeds 2-3″ apart, rows 12–18″ apart. Cover seed lightly, about 1/8″, and firm soil gently. Thin iceberg and romaine lettuce to one plant every 10–12″, other types 8–10″ for full size heads or 6″ for mini heads. Dry soil must be watered to ensure coolness and moisture, and for uniform germination.
HARVEST: Harvest young leaves for continual harvest of baby leaf greens. Allow to mature for full head harvest and use a garden fork to pull from bottom soil. Store in cool, dark and high humidity location for up to 2-3 weeks.