Extending Harvest With Succession Planting

As the summer wears on, our motivation to plant a garden probably is inversely correlated with the outside temperature.  However, August is an ideal time to plant vegetables for fall harvest. Vegetables maturing in the fall often are of better quality than those harvested in late spring or summer because of the cooler fall temperatures. By using the technique of succession planting we can provide for fall vegetables while at the same time making efficient use of our garden space. Working in the cooler temperatures of early morning or late evening will make the task more enjoyable.

Succession planting simply means that as one crop is harvested and removed from the garden, a second is planted in the area vacated. The same crop may be repeated or a different crop may be planted, depending on the date and/or food preferences of the gardener. Succession planting extends the supply of produce from the garden late into the year and helps to make optimum use of valuable garden space by growing two crops instead of one in a given area.

There are three classifications of vegetables that make good candidates for succession planting at this time of the year: 1) those that are damaged by frost but mature quickly before frost occurs; 2) those that mature relatively rapidly but can withstand a light frost; and 3) those that mature more slowly but can withstand freezing temperatures without severe damage.

Bush beans, bush cucumbers and summer squash are examples of the first classification vegetables. If planted in late July or early August, there is a good chance that these species will mature before frost, although fall gardens are always a gamble because of the unpredictable nature of the weather. If an exceptionally early fall with very cool nights should develop, production may be very poor even though frost has yet to occur.  However, if the fall is warm and long, late plantings of these species can be productive and rewarding.

Those vegetables that can withstand light frost and still be planted in August (group 2) include beets, Chinese cabbage, collards, lettuce (leaf and bibb types), spinach, Swiss chard and potato. Late potatoes, as a rule, are not very productive and do not store well. However, they often make a satisfactory crop of small, “new potatoes” when used as a succession crop. Seed potatoes that were left over from the spring may be  planted; do not plant potatoes recently harvest from a spring crop.

Vegetables that can be planted in August that are able to withstand fairly low temperatures (group 3) include broccoli, Brussels sprouts, cabbage, cauliflower, kale and turnips. All but kale and turnips should be set out as transplants. Seeds of broccoli, Brussels sprouts, cabbage and cauliflower planted directly in the garden will not mature before killing temperatures unless fall temperatures are atypically warm with very late killing low temperatures.

Fall garden peas can be very tasty but planting them in August is a gamble. In many cases peas do not have adequate time to develop in the fall before they succumb to freezing temperatures. Edible-pod (snow) peas are the best choice for fall peas since they produce pods that can be consumed at various stages of development.

The process of succession planting is fairly simple. When a crop is removed, it is very important to rid the area of plant debris as much as possible. This will help to eliminate insects and disease inoculum. Also, till the soil lightly and add a general purpose, garden fertilizer such as 5-10-5 or 12-12-12. If the soil has been productive the application of additional fertilizer might not be necessary. Growth must be rapid in succession plantings in order for them to mature before killing temperatures.  Therefore, a side dressing of nitrogen after the seedlings or transplants have become established can be helpful.

Since insect populations have had the opportunity to develop throughout the growing season, they represent a significant challenge for succession plantings. Removing the plant debris from the previous crop is helpful but regular monitoring still is required. Early intervention using integrated pest management (IPM) practices is recommended when significant populations of insects are detected.

Diseases, especially those that favor warm temperatures and moist conditions, can be less of a problem for succession plantings, especially if the fall is relatively dry. Again, regular monitoring should be practiced since there are diseases that thrive in cool, moist conditions.

Vegetables require between one and two inches of water per week. Although plants tend to transpire less water in the cooler temperatures of the fall, adequate moisture is still a concern and irrigation may be necessary during dry periods. If the soil has been allowed to dry out between the removal of the previous
crop and succession planting, make certain there is adequate moisture to support seed germination.

Finally, the use of frost protection measures such floating row cover can extend the growing season for those crops injured by frost. Floating row cover is a translucent, spun polyester material that traps the soil’s latent heat underneath it when it is spread over plants. It offers several degrees of frost protection and, since it is translucent, it can be left in place for days during periods of cold weather. It is relatively inexpensive and can be used for several years if care is taken when it is removed and stored.

Succession plantings can be challenging and there is risk involved. However, delaying the harvest of the last vegetables of summer late into the year tends make those of us who are avid gardeners feel that spring can’t be too far away.  (by David Trinklein, MU Horticulture, Associate Professor)