Lettuce is one vegetable I like to have all summer. It can be sowed continually as long as it has a certain amount of shade to cool the soil. If the soil is too hot lettuce seeds will not germinate. If you do get some growth, the heat can still make them bolt early so location is important. Mulching or planting lettuce near towering plants will ensure enough shade to encourage growth. Looking for lettuce seeds that tolerate heat will also help in maintaining lettuce all season long. Some examples include Green salad bowl, Black Seeded Simpson, Summer Bibb and little Gem. These are a variety of lettuce and include bibb, leaf, and romaine types. With the cooler temps going into the fall, lettuce will grow like it did in the spring. Sometimes I seed lettuce in smaller containers and transplant when space opens up in the garden. If it is a mild fall, having fresh greens for the Thanksgiving table is very likely.