The key is understanding the difference between cool season and warm season garden plants. Cool season plants are the ones we usually plant in spring. They include cabbage, lettuce, spinach, kale, peas, radish, beets, and chard. These plants can handle an occasional bout with cold temperatures. Warm season plants are the ones we plant after the last frost date. They include tomatoes, peppers, vine squash, and melons. When those plants experience frost they shrivel and die.
We can sow cool season plant seeds in early spring because the young plants aren't killed by late frost. Many gardeners know that it takes awhile for many of those seeds to germinate because of cold soil temperatures. When they do begin to grow, their productive season can be short because the heat of summer tends to affect them adversely and they flower, go to seed, and fade quickly.
Sowing these same seeds in late summer results in quick germination in the warm soil. There is no cold threat to the young plants and they grow quickly. As they mature and begin to fruit an occasional early frost may threaten, but the larger plants can shrug it off easily. There is absolutely no threat of high temperatures causing the plant to bolt so they produce fruit until they die.
That's one of the greatest advantages to planting a fall crop: the production of fruit is often longer and greater than spring crops. These plants often relish the cool temperatures and rather than respond poorly to hot days they respond richly to cold days. Many people think these plants produce tastier produce after they've been exposed to cold.
Treat your second season garden just as you would a spring one. Before planting, amend the soil and prepare the bed. A good dose of compost or aged manure is a nice boost to soil that has already been used for a recent crop. You usually have plenty of time to do this from when the plants fade in mid summer to when you plant in late summer.
Mulch becomes an important factor in the success of a fall crop. Mulch moderates soil temperature. In a spring planting for summer harvest, the mulch helps keep the soil from getting too warm. In a summer planting for fall harvest, the mulch helps keep the soil from getting too cool.
Be aware of different irrigation needs than you may be used to. The seedlings and young plants are beginning to grow when it's still hot out. A new spring bed may need watering twice a day to keep the soil moist. A new summer bed may need watering four or five times a day to stay moist. To help keep the soil from drying out quickly, I drape fabric over the bed to shade the soil until the plants establish themselves and the days begin to cool. Row covers and shade cloth are ideal.
Be ready for different growing characteristics. When I sowed beet seeds in spring it took almost two weeks for the first sprouts to appear; even cool season plants need the soil temperature to be warm enough to effectively germinate. The beet seeds I sowed in summer germinated after four days.
Many root crops are well suited as second season crops. Carrots, turnips, parsnips, beets, and radishes do well when planted up to two months before the first frost. For me that's early August, but for many gardeners that time extends into September or October. A thick mulch helps keep the ground from freezing early and affecting the growth and harvest of the roots.
Cabbage, green onions, spinach, cauliflower, snap and snow peas, should be planted a little earlier to ensure they complete their growth before cold sets in. For me that was mid July, but for many gardeners that time is now.
Tough greens like endive, mustard, chard, spinach can handle cold well. Chard, in particular, grows in snow and has a nice sweet flavor as a result.
Second season gardens offer advantages that are easy to overlook. The cooler temperatures affect weeds and garden pests too. Less weeding and pest management chores are definitely welcomed by most gardeners. Often, it isn't until you're reviewing the success of your growing season with the snows falling that you realize how easy the fall crop was to maintain.
When you use a method for extending your growing season you may be able to harvest vegetables well into December and winter. (Check out my March 2, 2011, article "Extending Your Growing Season With Mini Greenhouses").
Whether planned or by accident, take advantage of the growth characteristics of cool season plants and enjoy a second season. Grow a fall crop.