Why Use Row Covers?
Many insects find their food by sight. Some then communicate the find to their kin, at which point you get an infestation. The cabbage white butterfly, for example, seems to locate its favorites—broccoli, Brussels sprouts, cabbage, cauliflower, collard, horseradish, kale and kohlrabi—by the distinctive blue-green leaf color. You can use this knowledge to protect your plants: Simply hide them from sight under row covers.
Sometimes called floating row covers, these gossamer-thin synthetic fabrics protect plants from insects, cold and wind. Technically, they are spunbonded polyester or polypropylene. Even the thinnest types hide plants from insects’ sight, while the heaviest offer several degrees of frost protection as well. All allow water to pass through, so rainfall and overhead watering still reach the plants.
Three Kinds of Row Covers
The thickness of row cover fabric is measured by weight per square yard. The lightest type is half an ounce, while medium grades are around one-and-a-quarter ounces. The heavier covers that give maximum frost protection weigh in at two ounces. Covers are sold under several trade names, including Reemay, Agribon, Typar, Agronet, Harvest Guard and Agryl, all available in a variety of widths and lengths.
A medium-weight row cover will give from 2 to 6 degrees of frost protection and has about 70 to 85 percent light transmission. The heavier materials offer up to 8 degrees of frost protection, but they inhibit daylight transmission down to as much as 50 percent. Some growers use a double layer of fabric, with apparently good results.
The lighter row covers are so light they can “float” right on top of most seedlings. As the plants grow, they push the row cover fabric up. Medium and heavier grades need to be supported on wire hoops to form a low tunnel in which plants thrive.
Use and Maintenance
Installation is pretty simple, although it’s good to have an extra pair of hands to help with large pieces of row cover. Pick a calm day. If you are laying the cover flat over seedlings, allow enough slack to give the plants room to push it up as they grow. If you’re installing a row cover over wire hoops, drive a wood stake at each end of the row, to which you can tie the fabric. The sides need to be secured well or the wind will get underneath and blow your cover into the next county. Some people use rocks; others make a shallow furrow down each side of the row and bury the fabric edges with soil. I use metal staples made for this purpose. They can be reused, and they’re easy to remove when I want to check on the plants underneath.
With care, even the lightest row cover fabric can be used for two or three years. The medium and heavy fabrics should last five or six years in a garden situation. I keep the big cardboard roll the fabric comes on and roll it back onto that at the end of the season. Wrap it with paper (newspaper works), taping it to hold it in place. Any rips or tears in the fabric can be mended with clear packing tape.
Row Cover Problems
There are a few caveats to bear in mind. The growing tips of tomatoes and peppers can be damaged if the row cover touches them, and the row cover can break the stems of plants in the squash family in windy conditions.
Row covers will not protect against insects that emerge from the soil underneath, such as Japanese beetles, Colorado potato beetles, tomato hornworms, root maggots and flea beetles. This is one more very good reason to rotate your crops so they don’t grow in the same spot as last year. A pest that emerges near its target plant and finds itself protected from predators by a nice cozy row cover will decimate your plants even faster than usual.
Just as your plants will love the row cover microclimate, weeds will love it, too. Deal with this by first laying a drip irrigation line, then a long strip of plastic mulch into which you can plant your transplants. Cover with wire hoops and row cover fabric, and you’ll have warm soil, water where and when you want it, no weeds, and protection against insects and surprise frosts. It doesn’t get much better than that.
Click here to see what weight row cover is best for certain types of plants
Click here to read Peter’s favorite use of medium-weight row covers
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