In most parts of the United States, it's possible to have fresh vegetables from your home garden almost year round. The vegetables you grow may vary from one part of the year to another, because some vegetables are cold weather crops--meaning they don't mind the cold--while others are warm weather crops so they need the heat of summer to produce food for you.
Kale, collards, spinach, mustard, leafy lettuce and several herbs can all be grown in areas with mild winters. In fact, most of these leafy greens can tolerate temperatures down to 10 or 20 degrees, while some--like spinach--are fine down to 0. If your area gets even colder, you can sometimes continue growing greens under clotches, row covers or cold frames.
Choose early producer and cold hardy varieties of the leafy green vegetables you'd like to grow, then plant them in late summer so they have time to put on good growth before the days become shorter and their growth slows down.
Carrots, celery, turnips and parsnips are excellent examples of root vegetables that grow well through the winter. The trick with these is to plant them early enough in the fall to allow them to get a good head start in growth before the shorter days of late autumn and winter arrive. Many root vegetables such as carrots can even be stored in the garden the entire winter, and simply pulled up for use as you need them.
Cabbage, broccoli, cauliflower and brussels sprouts are further examples of tasty vegetables you can grow in a winter garden. In cooler areas of the country such as Washington, these can be direct seeded in early to mid July and in warmer areas such as Tucson Arizona they can even be seeded as late as September.
According to Oregon State University, these vegetables can handle temperatures down to 10 degrees, making them excellent choices for growing in a winter garden in mild winter areas of the States.
Like other winter vegetables, these also grow well under clotches, row covers or other cold weather protection in areas that are slightly too cold for them.