The No-spray Way to Protect Plants

Image Gallery Row covers work great to protect your crops from a wide variety of pests, including: cabbageworms, flea beetles, squash bugs, potato beetles, root maggots, leaf miners, cucumber beetles, army worms, grasshoppers, squash vine borers, deer, rabbits and birds. ELAYNE SEARS

In many organic gardeners’ storage sheds lurk what look like stashes of dirty bed linens. These are actually sheets of reusable fabric row covers, which serve as barriers between plants and those creatures that would destroy them. Without ever picking up a sprayer, you can use row covers to eliminate problem insects, and they prevent browsing by rabbits and deer, too. When combined with a weed-suppressing mulch (such as straw or grass clippings spread over wet newspapers), row covers often increase yields of peppers, strawberries and cucumber-family crops by more than a third.

Unlike plastic, which blocks rain and quickly heats up in the sun, the zillions of tiny holes in fabric row covers let rain in and heat out. Perforated plastic row covers do vent out hot air through thousands of holes or slits, but they are much less durable than breathable fabric row covers, which can be reused for several years and serve multiple purposes. With fabric row covers in place over your spring salad patch, you can stop worrying about biting winds and hungry rabbits. In summer, you can sleep easy knowing your melons are safe from four- and six-legged saboteurs that sneak in at night.

Lessons In Light

Garden row covers come in different weights, with thick versions such as Agribon 50 or various “frost blankets” providing up to 8 degrees of frost protection. The density needed to retain heat comes at a cost, however, because heavyweight covers admit only 50 percent of available light. This level of light deprivation nearly offsets these covers’ insulating benefit, though thick covers are great to use in late winter to promote heavy, early production of strawberries and fall-bearing raspberries such as the ‘Heritage’ variety.

Midweight row covers, such as Agribon 19, Reemay and Covertan 17, admit 75 percent to 85 percent of available light. They also provide 2 to 4 degrees of frost protection and excellent buffering of strong winds. The fibers in midweight row covers are dense enough to provide multiseason durability, but still porous enough to admit rain and ventilate themselves on sunny days. Should a serious cold snap hit, you can simply add a sheet of plastic or throw an old blanket on top of the row cover.

As the weather cools in the fall, midweight row covers are great for wrapping around caged tomatoes or peppers that are heavy with ripening fruits, or you can use them to keep aphids, leaf miners and flea beetles from finding your leafy greens.

Very lightweight row covers give little or no frost protection, but they also retain very little heat while admitting 95 percent of available light. These covers are standard equipment for excluding squash bugs, cucumber beetles and squash vine borers from young squash, cucumbers and pumpkins, or for keeping cabbageworms and root maggots from finding your broccoli. Row covers do need to be left off some plants to allow for pollination. Most vegetables that produce flowers before they make a crop, such as squash, cucumbers, tomatoes and peppers, require repeated visits from insects to spread pollen from flower to flower. Root crops and leafy greens need no pollination, so they can be grown under covers until they are ready to pick. Last August, a featherweight row cover held in place with clothespins spooked the family of deer that had taken to eating my ripening grapes for their breakfast.