How to Cover Plants for Frost Protection
In areas where a late spring frost or even an early fall hard frost can threaten garden and landscaping plants, there are ways plant lovers can protect them. Weather is unpredictable, even in those areas where plants are suitable for their growing zone. You can protect plants from frost if you are both preparedand aware of the pending weather.
Soft woods, actively blooming plants, and potted plants are the most susceptible to frost damage. The greatest threat of frost usually occurs overnight when the temperature drops enough to freeze the moisture on plant leaves and buds. The signs of frost damage are usually visible within two to three days and include browned and mushy leaves and buds. To protect plants from frost, you will need to cover them to keep the moisture from freezing.
Plastic can be used to protect plants from frost, but it’s not the best or most effective material, and some expert gardeners warn against it. Plastic or vinyl materials do not breathe, causing moisture to get trapped inside. If the temperature drops low enough, the increase in moisture presents a greater threat to the plants. Instead of plastic, try using natural fabrics like cotton or linen, an opened burlap bag, or newspaper, as a covering to protect plants from frost.
A fabric covering will allow moisture to escape but will still protect plants from frost by preventing the freezing air from coming into direct contact with the moisture. Bed sheets work well for covering large plants and shrubs, as well as young sprouts. Newspaper can be used on low-growing foliage, but won't stay on top of larger plants well.
In a pinch, you can use plastic sheets, but be sure to remove the plastic covers early in the morning to let the increasingly warmer daytime air reach the plants. If the threat of frost is prolonged and temperatures remain low during the day, be sure to use a fabric covering. When there is a threat of frost, cover your plants before sunset.
You can also purchase commercial coverings designed to protect plants from frost. These may be more attractive than other methods, but usually bed sheets or burlap work just as well. If your efforts to protect plants from frost fail, you will have to allow nature to take its course. Early spring perennial flowers like the daffodil, tulip, and crocus may be damaged for the current season, but they should return in good health the next spring.
Depending on the weather, some plants may peek out earlier than normal, only to be threatened by a late frost. In some cases, they will bud again but often they will die and you’ll have to start over. Typically, the more established a plant is, the better it will fare. If you have vulnerable plants that would be expensive to replace, it’s best to try to protect them.
The cold, cloudless evenings in the fall, winter and spring may be harmful to your plants. During the day, your plants and the soil absorb and store heat from the sun. As the day turns into night, your plants quickly begin to lose all of their stored heat. Clouds will help to insulate and slow the loss of the heat, but a cloudless, wind-free night will afford no protection from frost. The temperature within the soil and in the plant’s cells may even drop to a few degrees colder than the air.
As the temperature decreases, the moisture in the air condenses into dew, which then freezes when the temperature reaches 32 degrees F. on the plant surfaces. At 32 degrees, damage to most plants may be minimal and only affect a small amount of leaves. However, if the temperature drops far enough for the plant cells to freeze, non-hardy plants will die.
Frost can occur even in supposedly frost-free areas. It is important to heed the weatherman’s warnings of “a chance of frost,” and take precautions to protect your garden. It is possible to extend your growing season by several weeks if you are able to keep your plants alive through a single early frost!