In general, lettuce prefers cool weather and will bolt (flower) earlier in hot weather. For early head lettuce, start seeds indoors 3/1 at 68° (cover flat with a dome and expose seeds to light). Sow lettuce seeds outside anytime between 3/27 – 6/30. You can try to sow lettuce seeds 7/1-8/1 but lettuce seeds will not germinate when the soil temperature is over 80° - try covering seeds with row cover fabric to keep them cool and moist. Lettuce seeds need light to germinate - plant seeds on the surface of the soil and pat gently with a hand. Keep seeds constantly moist until germination. Days to germination: 2-14 days. Space head lettuce 10” apart. For baby lettuce broadcast sow seeds.
For the full crunch, harvest heads with a knife as they form a full size loose head but before they begin to bolt.
Lettuce is mostly self-pollinated and rarely crosses with other lettuces. Isolation distance: 12’. Minimum population size: 5-10 plants. Remove early bolting plants. If lettuce stems fall over, stake them. Harvest lettuce seeds as they begin to mature (they will form dandelion like white plumes on them). Harvest seeds by tapping stems to shake seeds into a bucket. It is best to harvest lettuce seed after several days of dry weather. Harvest seeds over several weeks.