Fall Vegetable Gardening

Get tips on what and when to plant for fall vegetable garden

Bill Sevier: Ask a Master Gardener

Saturday, August 1, 2015

Q: My vegetable garden I planted in spring didn’t do so well due to the rain and I would like to plant some fall vegetables. What can I plant and when is the best time? T.M., Tulsa

A: OSU has an excellent fact sheet, HLA-6009, "Fall Gardening", available on the Master Gardener web site — that offers what, when and how guidance to plant a fall vegetable garden. It also lists average time to maturity of each vegetable.

Several vegetables may be planted from now through September. Some will tolerate a few frosts and are termed as “semi-hardy”; the others can’t handle frosts and are termed “tender” vegetables.

The tender group of plants include bush, pole, lima and cowpea beans, as well as sweetcorn, cucumber, eggplant, pumpkin, summer and winter squash, and tomatoes.

The semi-hardy vegetables to plant now or later in summer are beets, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, collards, Irish potato, radish, green peas, Swiss chard, turnips, parsnips and leaf lettuce. One should wait until September to plant garlic, kale, kohlrabi, mustard, spinach and onions.

Some of these vegetables are planted as seed, others as seedling plants. Seeds left over from previous plantings should be viable for use if they have been kept in a refrigerator or freezer.

The major obstacle in starting a fall garden in summer is the challenge of hot soils and rapid water evaporation. Some seeds will not germinate at high soil temperatures, which in summer may be in excess of 140 degrees.

There are some work-arounds to cope with the summer extremes. One method is to plant both seeds and transplants in the bottom of a furrow a few inches deep. The bottom of the furrow is cooler, and a furrow also makes it easier to irrigate. After planting, either in a furrow or on top, shading the soil is desirable. One can use a straw mulch or garden shade cloth to help cool the soil. These cloths are available in most garden centers.

All plants in the fall vegetable garden will need to be watered until rains begin in fall. The best way to do this is to use drip irrigation. This type of irrigation is relatively cheap and easy to install for most homeowners. You may refer to OSU’s fact sheet for commercial drip irrigation, BAE-1511, “Drip Irrigation Systems” . The companies that manufacture irrigation products, such as Rainbird, also have useful manuals with instruction directed toward homeowners.

There are many possible approaches to a fall vegetable garden, all of which result in produce that some people would argue is even tastier than spring-grown. In addition, some of the semi-hardy vegetables may be harvested into the winter months, especially if a cold frame is used.

Garden tips

Divide and replant crowded hybrid iris (bearded iris) after flowering until August. When planting, take care not to plant the rhizomes too deeply. Cover them with an inch of soil or less. Do not mulch iris.

Water all plants deeply and early in the morning. Most plants need approximately 1 to 2 inches of water per week. Rather than watering daily, water less often and more deeply.

Some trees such as sycamores and river birches lose large numbers of leaves in the heat of summer. Trees do this to reduce water loss from their leaves. It is a coping action by the tree; it is not dying.