Good Life

Over the Garden Fence | Row covers extend garden production season

The recent cooler temperatures reminded me that the vegetable garden soon will be a thing of the past unless we think about providing some protection for the crops.

For some crops, think about using row covers that can float or that can be placed over a semi-circular frame made of 9-gauge wire or over a bent electrical conduit frame, making a low tunnel.

For most crops, floating row covers require no support because they are lightweight; they lie directly over the crop Materials include perforated plastic, spunbonded polyester and spunbonded polypropylene, and they do not impede seedling emergence or subsequent growth of the crop. To secure the cover against wind, all the edges are buried or weighted down with sandbags, rocks or other materials.

There are two types of these covers: perforated polyethylene, which is about 1 mil thick, and spunbonded polyester or polypropylene, which is available in several weights (rather than in thickness). Perforated polyethylene has a uniform pattern of 3/8-inch holes (74 holes per square foot) for ventilation. The holes allow for heat loss at night and are an entry point for insects. However, many growers and gardeners have found these covers to be beneficial for growth enhancement.

Spunbonded covers are comprised of a thin mesh of white synthetic fibers, which trap heat and serve as a barrier to wind, insects and varmints. Water from rain or overhead irrigation freely passes through. The weight of these covers range from 0.3 to about 2.0 ounce per square yard (10 to 68 grams per square meter). The lightest covers are used primarily for insect exclusion while the heaviest of the covers are used for frost protection. The most common weights are 0.5 to 1.25 ounce per square yard (17 to 42 grams per square meter). With covers under 0.5 ounce, there is minimal heat retention at night; and over 1.75 ounce, there is a significant reduction in light transmission. The heavy covers are used for nighttime frost protection only because they do not transmit sufficient light for optimum crop growth.

Spunbonded row covers in the 0.5- to 1.25-ounce range provide 2 degrees to 4 degrees frost protection in the spring. In the fall, there is more protection because there is a larger reservoir of heat in the soil than in the spring. These covers perform well in protecting late-season tomatoes and pepper from early frosts.

Floating covers require much less installation labor than hoop-supported covers. The wider and longer the covers, the less labor required per unit area because only the edges are secured. These covers vary in width from 6 to 50 feet and up to about 800 feet long.

Most vegetable crops, as well as strawberries, raspberries and cut flowers, have been grown with row covers. Although the primary crops for row cover use are high value crops such as melons, tomatoes, pepper, summer squash, sweet corn and strawberries, many growers find row covers to be valuable for a number of crops for varying reasons — earliness, higher yields, overwintering protection, and insect and varmint control. Crop distinctions such as temperature sensitivity, pollination methods and growth habit dictate the type of row cover that is best to use.

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