Although Oklahoma gardeners are still reaping the rewards of their spring gardens, it's time to start fall gardening.

David Hillock, Oklahoma State University Cooperative Extension consumer horticulturist, said some of the best quality garden vegetables are grown during the fall season.

"Successful fall gardening begins much earlier than the fall season. High-quality results are available during the fall when warm, sunny days are followed by cool, humid nights," Hillock said. "Under these climatic conditions, plant soil metabolism is low; therefore, more of the food manufactured by the plant becomes a high-quality vegetable product."

Although much of Oklahoma has received heavy rain recently, climatic conditions in August typically involve high soil temperatures, high light intensity, and rapid soil drying. This can result in difficulty obtaining a uniform stand of plants. With lower-than-normal temperatures, gardeners may not need to use special treatments such as shading rows when seeding or supplemental watering to reduce soil temperature.

Hillock said that, to germinate or sprout, seeds must be viable, have the proper temperature, adequate moisture and sufficient oxygen.

"The surface of the soil, when exposed to the summer sun, may become very hot (140°F or 60°C).  Vegetable seeds should be planted no deeper than three times the diameter of the seed," he said. "With a small seed such as a carrot, this would be no more than 1/4 inch deep. At this depth and exposed to the hot soil, seed death due to high temperatures would probably occur. It's also likely that such soil, even when watered, might dry out quickly due to the high temperature. Unless the soil remains moist at the depth where the seeds have been planted, germination will not take place."

To achieve proper temperature and adequate moisture, apply mulch over the row after planting and watering, or use materials such as screen wire strips, shade cloth, or boards to cover the row. This will moderate both soil temperature and soil moisture. Remove covers after the seedling emerges. 

Hillock said broccoli, cauliflower, Chinese cabbage, leaf lettuce, Brussels sprouts and cabbage do well when planted from seed in a small seed flat, grown in individual containers for about a month, then transplanted to the garden.

"Before setting them in the garden, transplants may be conditioned or toughened by a reduction in the amount of water supplied and by exposure to full sunlight," he said. "This might require three to five days. Plant them in the garden in late afternoon to early evening to reduce transplanting shock. As they are set, water the plants using a starter solution."

For more in-depth information about fall gardening, check out OSU Cooperative Extension Fact Sheet HLA-6009 at osufacts.okstate.edu and type fall gardening in the search tool.