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.
Working with fabric row covers may seem awkward at first, because the lightweight fabric tends to blow around while you’re putting it in place if there’s even a small breeze. The fabric also tears easily on sharp edges. But with a little experience, you’ll learn how to work with the material. Here are some tips for getting the best from row covers:
- Row covers are available in small pieces that are easy to manage, but it’s more economical to buy a larger roll and cut pieces to fit as you need them.
- The quick and easy way to anchor row cover is with rocks or soil, but this also tends to tear the fabric quickly. Instead, try using plastic soda bottles partially filled with water as weights, or make “sandbags” by filling plastic shopping bags partway with soil.
- Wire hoops, which you can buy from garden suppliers or make yourself from 9-gauge wire, are perfect for supporting row covers over garden beds. Use hoops both under and over the fabric to hold it in place.
- At the end of the season, shake the covers to loosen dirt and debris, and make sure they’re dry. Fold or roll them and store them in a plastic storage bind for winter, either in a garden shed or outdoors. Weight the cover of the tub with rocks or bricks to keep it tightly closed.
- If a piece of row cover is torn in several places, cut it up into small pieces for patching larger sections of cover that have small holes. Waxed dental floss works well for “sewing” the patches.
- To protect upright plants with row cover, put a small tomato cage in place around the plant and wrap row cover fabric around the cage, pinning it in place with clothespins.
For more information about extending the growing season, see our article about Cold Frames.