It is the rare gardener who finds the growing season long enough. Fortunately, gardeners can satisfy the itch to plant early and to keep crops producing through fall by using row covers. Made of light, permeable material, usually polypropylene or polyester, row covers can be laid loosely on top of plants or supported with wire hoops. They’re available in different weights that provide varying degrees of frost protection.
Floating row cover: The lightest-weight row covers, also called floating row covers, allow air, water, and up to 85 percent of ambient light to pass through. They provide only a few degrees of frost protection, but they are an excellent barrier against damage by a wide range of pests.
You can cover newly seeded beds or pest-free transplants with floating row covers, leaving plenty of slack in the material to allow for growth. Be sure to bury the edges in the soil or seal them in some other way. Otherwise, pests will sneak in and thrive in the protected environment.
You can leave row covers over some crops, such as carrots or onions, all season. Uncover other crops, such as beans or cabbage, once the plants are well grown or the generation of pests is past. Plants such as squash that require pollination by insects must be either uncovered when they start to flower or hand pollinated. In a hot climate you may have to remove covers to prevent excessive heat buildup.
Heavier covers: Gardeners can also use heavier row covers to protect plants from freezing and extend the gardening season. These row covers can provide as much as 8 degrees of frost protection. They also block more light, so plants underneath them may not grow as quickly. Or, you can get a similar effect to heavy covers by using two layers of a lighter-weight cover.
Plastic row covers: Row covers made of plastic or slitted plastic require careful management because temperatures under plastic row covers can be as much as 30°F higher than the surrounding air. You will need to vent them on warm days and close them back up at night. Slitted plastic row covers don’t require venting. Colored or shaded plastic covers are available for Southern gardeners. The coloring blocks out some of the sunlight, reducing the heat inside the tunnel. Suspend plastic row covers over the row with metal, plastic, wire, or wooden hoops to prevent injuring plants. Anchor row cover edges securely in place with soil, boards, pipes, or similar material.