Polyester for your plants. Keeps out bugs, lets in air and water

SPUN-bonded polyester. Anyone handy with a needle and thread knows it as interfacing, the lightweight fabric used to add substance to such things as collars, lapels, belts, and perhaps cuffs. But increasingly gardeners and farmers in the United States and Canada are seeing it add substance to their harvests as well. Broad bands of the fabric are being used as loose-lying row covers to get early-season crops off to a fast start. The University of New Hampshire tested it over several seasons and came up with some promising figures. Commercial vegetable growers have done the same thing, and more recently gardeners have come into the picture.

A few years back the enterprising Swiss produced the first of these expandable covers by inserting multiple rows of tiny slits in polyethylene plastic sheeting. The slits allowed air and water to pass through and also allowed the plastic to expand somewhat as the plants grew. The British, in particular, tested the Swiss product and found it boosted production noticeably. But it had some drawbacks: Because of the slits the plastic tore rather easily, and sometimes growing plants became entangled in the tiny slits and were uprooted when the plastic was removed.

Meanwhile, here in the US the Du Pont company realized it had a fabric with superior handling characteristics to poly which might be similarly beneficial for the crops growing beneath it. That product was Reemay, used as interfacing in clothing manufacture, among other things. Test consignments were sent to the Department of Plant Science at the University of New Hampshire, in Durham.

Reemay is spun-bonded polyester, so light (0.6 ounces to the square yard) that plants readily lift it as they grow. It is applied to the farm rows or garden beds with enough slack in it so that the plants are not held down as they grow. According to Dr. Otho S. Wells of the University of New Hamsphire, Reemay's chief feature is that it holds enough heat to advance early-season growth, yet is porous enough to self-ventilate. Manual ventilation is never required, he says. This same porosity also means that irrigation is not hampered in any way. It transmits 75 to 80 percent of incidental light.

Reemay should not be looked on as a frost protector, although it will shelter seedlings down to about 28 degrees F. Much as a knitted sweater works for a human being, Reemay traps a layer of somewhat warmer air around the seedling and screens it from the chill winds of spring.

Apart from speeding early growth in the spring, it also offers protection from insects. Don Wilson, a New England vegetable grower and partner in Wilson Farms Inc., used Reemay to speed up early growth of beans and found that intercropped rows of radishes were completely free of root maggots. Apparently the parent flies couldn't get in to lay their eggs.

Master gardener Leslie Turek of Watertown, Mass., also harvested blemish-free radishes after he tried Reemay. In addition, he found it kept leaf miner out of his spinach.

Yet another plus: It prevented the birds from nipping off the shoots of peas, beans, and lettuce. Reportedly it also keeps maggots away from cabbage roots and worms off the cabbage leaves.

Reemay is laid loosely over the garden bed and held down by burying the edge three inches deep in the soil. It biodegrades after three months' exposure to intense sunlight. But because most gardens would use it for about half that time in the spring, it is expected to last for at least two seasons.

Commercial growers can buy Reemay at farm supply companies; garden-size lots are available in 67-inch widths from Gardener's Supply Company, Elm Street, Winooski, Vt. 05404.