You should be able to grow tomatoes, peppers, and cucumbers up until frost. Not sure when you start getting frost in the fall, so be prepared with a row cover if possible. As for greens, it depends on what type. Spinach, kale, mustard greens can take the cooler weather and do not like hot weather. Since I don't know what zone you're in it's more difficult to answer. I live in zone 7 and can usually grow peppers, tomatoes, squash and the like up until late October unless we have an early frost. Last year the plants lasted up until Thanksgiving before we got hit with the cold weather. Onions are difficult to grow in certain areas. Be sure that you buy Short Day varities. The Long Day types will only grow in warm areas like CA, FL, AZ. Good luck with your garden!!!