Cool-season vegetables are the best ones to plant for a winter vegetable garden. These include cabbage family (cabbage, broccoli, cauliflower, Chinese cabbage, Oriental greens, kohlrabi, etc.), radishes, green onions, peas, spinach, and mesclun. Timing depends on the average first frost date and the days to maturity for the vegetables you plan to plant. Because days are shorter in fall than at spring planting time, it's often a good idea to add a couple weeks to the stated days to maturity on the seed packet. Plant early enough in late summer so that the crops will mature before a hard freeze. You can also extend the season by using floating row covers or other frost protection devices.