Running for Cover

Extend your garden’s growing season by protecting plants against early frosts.

| August/September 2002

Row covers are made of a breathable material that transmits air and water through it. 

Gardeners can’t outrun Mother Nature. She determines when we stop or start our gardening season, but with a few tricks, we can stay ahead of her for as long as possible. Row covers are one way. Include them in your gardeners’ bag of tricks to wring extra weeks and months out of your growing season.

Row covers are terrific multi-tasking tools that extend growing and harvesting time by protecting plants from frost and drying winds and minimizing transplant shock. In areas with milder winters, using row covers over cold-hardy edibles extends harvesting into winter. Row covers are also extensively used for organic pest control. They form a barrier against insect pests and keep birds from stealing bramble crops. During the summer, row covers make good shade cloth for propagating cuttings.

Until row covers were developed, home and commercial gardeners used rolls of clear plastic over plant rows to create a greenhouse effect. This worked well to warm air and soil, but had drawbacks: plastic was unwieldy to work with, air couldn’t circulate (which led to fungal problems) and on warm days, it got too hot inside, which quickly dried out soil and baked plants. Impermeable to water, the covers had to be removed to water plants or drip irrigation had to be used.

Versatility for all seasons

Admittedly trapping less warmth than plastic covers, the newer fabric row covers have important advantages over plastic. Today’s row covers are made from extremely lightweight, loosely spun polyester and polypropylene, which make a material that, like plastic, transmits sunlight, but unlike plastic, is a breathable material that transmits air and water through it. Depending on the thickness, row covers allow from 60 to 90 percent light transmission and provide frost protection to about 24°F. They can increase ambient temperatures by 10°F.

Because the covers are so lightweight, they can be placed directly on plants. With just the edges secured with rocks, stakes, or soil, as plants grow, they naturally push or float up the covers, eliminating the need for wire hoops. (They are also known as floating row covers.) While they can be placed directly over plants, especially low-growers such as thyme, prostrate rosemary, dwarf lavenders, and even strawberries, I prefer to use them over wire hoops because under windy or heavy rain conditions, covers draped on plants such as basil can cause stem breakage.

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