When planting lettuce, look for disease resistant and heat and bolt-resistant cultivars for….

Summer crops. Lettuce does best in air temperatures 60°-65° with soil temperatures a minimum of 35°. Soil any cooler will see slow to no germination. Lettuce seeds germinate best at soil temperatures 40°- 80°. They won't germinate at all if soil temperature is over 85°. If weather gets hot, 80° or warmer, lettuce will bolt and turn bitter.