It may be difficult on a steamy hot summer day to think about the cooler weather and shorter days that lie ahead as the seasons change. But if you'd like to continue to reap a homegrown harvest into the fall -- or even winter, depending on your climate and the protection you give your crops -- now is the time to start planning and planting.
Cool season crops are naturals for fall harvest. Cole crops, greens, and root crops are all good choices. And some crops, such as kale and Brussels sprouts actually taste sweeter when harvested late in the season after they have been touched by frost. In areas with mild winters, like southern California, the Gulf Coast, and warm parts of the Southwest, you may even be able to grow cold tolerant crops throughout the winter.
So what's the secret to fall gardening? Planning ahead! As we mentioned, in order to reap a fall harvest, in most parts of the country you need to think about planting before autumn arrives. You may be busy picking beans, corn, and tomatoes, but you also need to take time out to plant seeds of crops so they will be ready for harvest in the fall. Crops that take longer to mature, like cole crops and root crops, will need to be planted earlier than quick maturing crops like spinach and lettuce. And you need to keep the expected date of your first fall frost in mind. Gardeners in shorter season areas will need to get seeds and transplants in earlier in the summer than those in areas where frost holds off until late fall.
To figure out what to start when in your climate, begin by figuring out the date of the first expected killing fall frost. While tender crops like beans and basil will be killed by light frost (below 32 degrees F), many cool season crops survive until hard frost, when temperatures dip below 28 degrees F. Especially hardy kale, cabbage, collards, and Brussels sprouts can withstandhard frosts, but will be killed when temperatures get down to 20 degrees F. or lower. To figure out when these temperatures arrive in your area, check with your local Extension Service or check out information available online from NOAA.
Next note the days to maturity (DTM) for the particular crop and variety you plan to grow. (Check the seed packet or catalog info to see if the days to maturity are from direct seeding or transplanting. If the DTM are from transplant to harvest, add another 2-4 weeks if you are growing your own transplants from seed.) When possible, choose varieties with the shortest DTM for fall harvests.
Add to this the length of the average harvest period. Then add in a fall factor of about 14 days. The fall factor takes into account the slower growth of plants as the days get shorter and cooler in late summer and fall.
Add up the days to maturity, the harvest period, and the fall factor. Then count back this number of days from the fall frost date to arrive at your planting date. If you plan to protect your crops with a cold frame, cloche, or low tunnel, you can plant 2-4 weeks later than you would for unprotected crops.
Salad Greens: Crops such as lettuce, spinach, arugula, and mesclun are great for fall harvest because they mature quickly, grow well when the weather is cool, and are less likely to bolt or go to seed than spring planted crops. Both spinach and lettuce germinate poorly in warm soil (above 60 degrees) so if you are starting plants in late summer, cover beds with shade cloth after planting or start seeds indoors and transplant.
Hardy Greens: Fall is a great time to grow these nutritious crops. Kale, collards, Swiss chard, mustard greens, and bok choy all thrive in cooler weather. A few light frosts will even sweeten the taste of your kale. If you plan to harvest kale at full size, plant it about two months before your frost date, but if you are growing it as "baby" greens, you can sow seeds just a few weeks before frost.
Cole Crops: Like kale, Brussels sprouts taste best after sweetened by a light frost. But it takes a long time to mature, so be sure to get it on to your planting schedule in early to midsummer. Other cabbage family members that are suited to fall harvest include broccoli, cabbage, kohlrabi, and cauliflower.
Root Crops: Beets, carrots, turnips, and radishes are all suitable for fall harvests. Root crops that mature in the cooler weather of fall will be sweet and mild. In the warmest areas, you can grow these crops right through the winter months.
Peas: These grow well in the cooler weather of fall, but can be damaged by frost, especially the developing pods. So try to time your fall pea sowing so plants mature a week or two before the fall frost date, and be prepared to cover plants if an early frost threatens. Keep the seed bed well watered to ensure good germination.
Q: My tomatoes always seem to crack just as they are getting ripe. What can I do to prevent this?
A:Cracking occurs when a tomato suddenly enlarges too quickly as it ripens. Cracks usually occur at the stem end of the fruit, sometimes forming concentric circles, sometimes radiating out vertically. When tomato fruits are at the mature green stage and the water supply to the plant decreases, the tomatoes begins to ripen, causing thickening of the outer layer of skin. Then if the water supply increases again suddenly, as when heavy rain follows a period of drought, the fruits enlarge rapidly and this tough outer layer cracks. Some varieties, especially older ones, are especially prone to cracking. To control this problem, try to keep soil moisture consistent by watering regularly, especially as tomato fruits are maturing, and make sure the soil around the plants is well mulched.