Lettuce all summer

To grow lettuce in summer, choose a heat-tolerant variety and give the plants some shade. Place them in a spot in the garden where they'll be shaded by taller crops or you can rig up some relief from full sun with cardboard or shadecloth. When temperatures climb above 90 degrees F., lettuce seeds won't germinate and so will need to be started indoors and planted in the garden after they're an inch tall.