Mid- to late summer is prime time for gardeners — a last chance to grow a second batch of fresh vegetables before the plant-killing frosts arrive. Add a few protective enclosures, such as cold frames, overhead sheets and hoops, and the harvest can be extended until Thanksgiving and beyond. "The goal is to have fully grown, ready-to-pick plants that basically store themselves in the garden throughout the fall, so you can pick them as you need them over a long, sustained garden season," said Renee Shepherd, founder of Renee’s Garden Seeds in Felton, Calif.