Autumn is a great time to plant native plants of many types, bulbs and some other cold-hardy perennials. You won't have success with tomatoes, zucchini, green beans, cucumbers and other warm-season annuals, but in many climate zones you can plant cabbage-family plants such as broccoli, cabbage, Brussels sprouts and kale. Lettuce is another food crop you can plant in fall, and so are snow peas and cool-weather herbs like cilantro---if you don't have extremely cold winters, these plants can provide your Thanksgiving dinner table with some fresh goodies.
Start seeds in pots in late summer for crops such as broccoli, cabbage, Brussels sprouts, kale, lettuce, snow peas and cilantro (coriander). Keep them where they will get filtered sunlight, but make sure the area stays under 80 degrees Fahrenheit.
Purchase bedding plants for the plants you want to grow in autumn, if you prefer. Seeds for plants that are native to your region might be difficult to locate, but many nurseries carry young plants.
Plant seedlings and young purchased plants in the soil before your first autumn frost. Dig plenty of humus or compost into the soil first, then dig holes for your plants and fill in with the soil you dug out. Water the newly planted area thoroughly.
Plant lettuce and other crops that might get frozen in a cold frame or greenhouse, or cover them with a floating row cover if you live in an area that receives hard freezes.
Plant many different types of spring and summer flowering bulbs in fall. Amend your soil with bone meal, blood meal and compost and then plant bulbs according to package instructions for the particular variety you have chosen.
Spread a thick layer of mulch, such as wood chips or compost, around the base of all plants to keep the soil warmer than it would be if it were bare.