Lettuce prefers cooler 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. Lettuce seeds germinate when the soil temperature ranges from 35-80° (68° optimum). 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 (laying row cover fabric on top of the seeds will help keep them cool and moist). Broadcast sow seeds for baby leaf lettuce. Days to germination: 2-14 days. Space 8-10” apart for head lettuce. This lettuce is very cold hardy and can be grown into the fall. Sow it around 8/15 during a cool spell (lettuce seeds will not germinate if soil temperatures are over 80°) - try covering seeds with row cover fabric to keep them cool and moist. Grows great in a hoophouse/cold frame and will survive winter with good protection.
Heads: Ruby Zoisite will make a small tight head (about 4-6” diameter). Harvest head with a knife at full size before it begins to bolt. Alternatively, harvest individual leaves but don't take more than 1/3 of the leaves at any time.
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.