Most of us think of planting in the Spring and harvesting in the Fall. And, for the majority of crops, that's right.
But species vary, climates vary and indoor container gardening often can be carried out all year round.
In some cases, it's actually very helpful for next year's crop to plant in the Fall. Many of these are designed to be plowed under rather than harvested, in order to enrich the soil for next Spring. In other cases, like certain lettuce varieties, you can plant late in the Summer and still harvest before the frost.
When to plant depends on the species and your climate zone. Get the best estimate possible on when to expect the first frost. 30-day weather forecasts, Farmer's Almanac and others are good sources of information.
Be sure to clear your area of any spring or summer crops before planting new seed or transplanting new vegetables. Leftovers decay, encouraging bacteria. Spread a couple of inches of new compost or mulch over the area. Turn the top layer of soil up and water well, then let it rest for a day. Since in most areas, you'll receive more rain (and sometimes snow) in the Fall, be sure you have well draining soil.
There are many varieties that will thrive if you take these preliminary steps.
Beets do well if planted before the beginning of August. If you intend just to harvest the tops, the date can be extended to the beginning of September. Try some Winterkeeper.
You can transplant broccoli until about mid-August. It will continue to thrive in most climates until Thanksgiving, when it can be harvested for a great addition to the holiday meal. In some warmer zones it may even last as late as Christmas. Italian broccoli can be planted over Winter in areas with no snow and will produce shoots until Spring.
Fall cabbage planting is common in many climate zones. Jersey Wakefield is often seeded in the first couple of weeks of September and will winter over well. Then it can be harvested in late Spring.
Carrots, since as a root vegetable the food actually grows under the ground, will last through just about anything. If you plant by mid-July or even in the Fall, you can harvest in Winter, provided there's little snow on the surface. Very cold temperatures will freeze the ground, making digging almost impossible.
Endive does well if planted by mid-July. A light mulch will keep it protected from frost and it can be harvested in Winter (again, assuming at most only light snows). Make sure it doesn't get drenched. Drainage in the Fall and Winter months is much slower than in Summer.
Romaine can be sown in July, then harvested in the Fall. Since it's low to the ground and very leafy, it's important to keep it from being excessively wet. Fungal growth is still possible in Fall, even though temperatures are cooler at night.
Plant some peas in early November, then harvest them the following June. That way you get vegetables to eat while you are still planting your other species.