When the weather gets cold, we pull on sweaters or button our coats. The extra insulation holds our bodies' heat inside the protective coverings. The same principle works for garden plants. Like a coat for the garden, a floating row cover will keep the cold night air and chilling winds away from tender leaves, trapping the soil's warmth close to the ground around plants. However, these blankets can be employed for much more than just frost protection. Whether you are setting out tender new plants, gardening with minimal rainfall, keeping insects at bay, or even providing welcome shade, floating row covers have proven to be a tool gardeners use to get the most for their efforts in the garden.
Just as a person living in Minnesota will need a heavier coat than one living in Georgia, not all gardens need a thick covering. Floating row covers, or frost blankets, are available in a range of thicknesses. Thin coverings allow about 70 percent of sunlight to reach plants, but they give minimal protection, usually to about 28 degrees. On the other hand, thicker coverings may shade out all but 30 percent of sunlight, but protection is better, usually about 24 degrees.
Whether you support your floating row cover or not, it needs to be anchored along its perimeter to hold it in place and to maintain its protective properties. Holding the sides down to the ground may be as simple as putting a brick on it to weight it down. Digging a shallow trench allows you to set the row cover in the trench and then anchor it by shoveling the soil on top of it. You can also buy 2-pronged staples to pierce the row cover and pin it to the ground.As implied by the name, floating row covers can be draped across plants without support. The material is similar in feel to interfacing fabric used in sewing. Made of polypropylene, they will not absorb water and become heavy after a rain. However, they will insulate plants better if supported above the plants. One way to do this is by creating a low hoop house over your garden bed. When the covering is not needed, just remove it, but let the hoops remain, making installation even simpler in the future.
When not in use, floating row covers can be folded and stored indoors or in a garden shed. How long they last depends on many variables, such as how often and how long they are used, how they are anchored, and mishaps such as wildlife or high winds. Like tomato cages, they don't last forever, but for a minimal investment, you'll get seasons of use from your floating row cover.
Here are reasons why you may need to use one in your garden:
Early Fall Frost / Late Spring Freeze
While frost protection into the 20s may not sound significant, the cold hardy crops of fall and spring naturally tolerate frost into the mid and sometime low 20s. That means that floating row covers will extend their hardiness into the teens. If you are worried about an early planting of tomatoes, peppers, squash, or other summer vegetable, you may want to cover them on cool nights or until temperatures are dependably warm.
Reducing Transplant Shock
Seedlings may not be fully prepared for the ravages of full sun, cold nights, or hot days in the garden. In either the cool or warm season, giving them the shelter of a row cover for a few days to a week will allow them to put down roots and make the adjustment from greenhouse seedling to garden plant.
Most of the moisture absorbed by plant roots is lost through pores in the leaves called stomata. This evaporation cools foliage in the hot sun and prevents damage to tissues. However, if rainfall is in short supply, a row covering can help shade foliage, reduce moisture lost to the air, and raise the humidity around plants in an arid garden, thereby reducing the need to water.
While good air circulation helps prevent disease, you can have too much of a good thing. A location with a nonstop or prevailing wind will dry out more quickly, putting plants under stress and reducing their productivity. Until you can construct or grow a windbreak, floating row covers can be used vertically on a wire fence or between vertical supports such as tomato cages to reduce the drying breeze.
It is always sad when a few hot spring days make the lettuce stop growing and begin flowering. As spring progresses towards summer, the addition of floating row cover over a lettuce bed can extend the season of harvest by keeping plants cool and productive.
If an insect can't reach a plant, it can't feed on it or lay its eggs. Lightweight row covers can be used with insect-plagued plants like yellow squash without blocking too much sun or putting pollinating bees in danger. After all, squash vine borers make the season much too short! Of course, flowering plants will not be able to set fruit if the bees cannot reach them. In areas where borers are only a problem early in the season, uncover plants once flowering begins. Otherwise, keep a small watercolor brush handy, lift the cover, and pollinate the flowers by hand.