Fall is an excellent extension of the vegetable garden season and a vital period for intensive gardening methods. Many cool-season and some warm-season vegetables attain their peak quality when grown and harvested as late crops. When planning for the fall garden, gardeners should consider the space needed, soil preparation, rotations and varieties desired. Seeds that were purchased for spring planting can be used for the fall garden provided they were stored in a cool location and kept dry.
The main challenge with fall vegetable production of cool season vegetables is seeding or transplanting a crop when the weather is hot. The latter makes getting good establishment and vigorous early growth more challenging. When seeding in late summer for a fall crop, moisture is often an issue. Water should be applied immediately after seeding or transplanting. Plant the seeds slightly deeper than you would normally plant them in spring to improve moisture availability for germination and root growth.
Cool-season vegetables will thrive in the cooler nights of late summer and fall and are not sensitive to frost. Since it is difficult to get uniform seed germination and seedling emergence in the high soil temperatures common in late summer, consider transplanting hardy crops such as broccoli, cabbage, cauliflower, and Chinese cabbage in early to mid-August for fall harvest. These crops should be four to six weeks old when transplanted into the garden. Transplanting in late afternoon or early evening will reduce transplant shock.
Greens (collards, kale, mustards and turnips) and lettuce are also well adapted to fall garden conditions. Greens can be seeded through August and harvested approximately 50 days from seeding. Turnips can be planted to produce greens or roots, depending on the variety. Both lettuce and spinach grow well in the fall and an ideal time for seeding is the first week of September (Labor Day weekend). Spinach often overwinters successfully and produces abundantly in April.
Many warm-season vegetables can be grown successfully in late summer and fall, including fall tomatoes, snap beans and squash (summer and winter). Snap beans can be seeded in early to mid-August in most areas of Missouri. Bush beans grow best at temperatures from 75 to 85 degrees but will drop flowers if temperatures exceed 90 degrees. They mature in approximately 60 days and make an excellent fall crop.
Since the last planting date for tomatoes, peppers, pumpkins, squash and cucumbers has passed, review the plants you already have and determine if they might benefit from additional or more regular watering, an additional application of nitrogen, or treatment with a fungicide or insecticide for pest control. Remember that most warmseason vegetables are tender and must be harvested before frost. Any tomatoes left on the vine when frost is predicted can be harvested green for green tomatoes, or, if they have started to turn, can be stored in a paper bag or wrapped in newsprint to ripen inside at 70 degrees F. Pumpkins and winter squash are sensitive to cool temperatures, but the fruit is often harvested after the first frost. For information on planting dates recommended for vegetable crops see the MU Guide Vegetable Planting Calendar: http://extension.missouri.edu/explore/agguides/hort/g06201.htm.
REVISED: August 1, 2012