Growthspurts 7-19-08

With temperatures soaring and the sun glaring, it is hard to think ahead to fall. But mid July is the right time to start planting several vegetables for a fall harvest.
When selecting vegetables for fall plantings, choose varieties that have a short maturation period. Planting time will depend on the length of time needed to produce a crop. Tender vegetables must be started early enough to ensure harvest before frost kills plants. Other crops, mainly root crops, are hardy enough to be stored in place in the garden well into winter.
Getting your fall vegetable garden started can be tricky when the weather is hot and dry. In the heat of the summer sun, the surface of the soil can reach temperatures of 140 degrees Fahrenheit. These temperatures can quickly kill plant seeds, especially small seeds near the soil surface. Water can also be a limiting factor in late summer, when intense sun quickly dries soils.
The following techniques can be used to reduce soil temperature and manage soil moisture.
• Plant in Furrows — One way to reduce soil temperatures around the seed is to plant in rather deep furrows. Before digging furrows, loosen the soil and incorporate a large amount of organic matter, which will help increase the water-holding capacity of the soil. Place the seeds in the bottom of the furrow and cover with soil, but do not fill the furrow entirely. The surface of the seed bed should be set considerably lower than the surrounding soil. The seeds will be shaded down inside the furrow.
The furrow also helps conserve water and direct water where it is needed, to the germinating seeds. When you irrigate your planting, water only in the furrow. Water will naturally fill the low spot you have created, fostering seed germination.
As the seedling grows, add more soil to the furrow bringing it level with surrounding soil. Place mulch around the plants to help retain soil moisture while also combating weeds. Weeds tend to be a greater problem in fall gardens than in spring. The constant supply of water favors weed growth as much as it does vegetables. Be sure to remove weeds that establish within the row.
• Provide Shade — Another way to help seeds develop is to provide extra shade. Shading will both reduce soil temperature and limit evaporation of soil moisture. You can provide shade using shade clothes, strips of screen, or boards to cover the row. Old wire screens work very well for shading rows. They are pliable enough to bend into tents over the row, yet sturdy enough to maintain the tent shape.
Be creative and use materials you have on hand. The goal is to cool the soil, creating an environment conducive to seed germination. Make sure to secure screens and other shade structures to keep them from blowing away with the wind. Remove any materials used for shading once seedlings emerge.
• Irrigation — Proper watering is essential to establishing any crop as seeds require constant moisture to germinate. This time of year, you will most likely need to provide supplemental irrigation, as rainfall is typically sparse. Using the furrow method will help you accomplish this task while minimizing water use. Drip irrigation is also very efficient.
Another helpful practice is to soak seeds overnight before planting. The seeds will imbibe or absorb water, hastening germination. This practice is not recommended for beans (Phaseolus spp.), because the seeds may crack and germinate poorly with too much moisture.
Oklahoma’s long growing season allows us to grow vegetables well into fall. The warm days and cool nights of autumn are ideal for producing hardy vegetables and leafy greens. Proper planning and preparation will ensure you have a desirable selection of plants available and the tools you need to establish plants during the summer heat. A little extra effort during establishment will be greatly rewarded with fresh produce in autumn.
Fact Sheet HLA-6009 <http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1114/HLA-6009web.pdf> is available at the Extension office and lists plant varieties and fall planting times.
If you have questions concerning this topic or related topics, call the OSU Extension Center at 273-7683, stop by the office or visit our Web site at http://www.oces.okstate.edu/pottawatomie/.