Lettuce, spinach, broccoli and other cool-season crops bolt and become bitter during these hot summer days. So if you haven't already pulled them from the garden now is the time to dig them up and reseed for harvest in September.

The first frost usually falls in mid-September, but can vary by a few days to a few weeks. As the frost date approaches, be prepared to cover your garden. There are several techniques that can extend the growing season well past the frost date. Cold frames, grow tunnels, row covers and hot caps can be used to protect plants from frost damage.