Some plants are well adapted to surviving periods of cold weather when temperatures drop below freezing, but frost-sensitive plants can be severely damaged or even killed by a hard frost. In areas that rarely suffer from cold weather, gardeners often plant tropical or semi-tropical plants that can be damaged by an unseasonably cold winter or an early or late season frost. When cold weather is predicted, it is important to protect plants from frost to prevent damage or death.
Plants are most likely to be damaged by frost when they are producing active new growth. This can occur when a hard frost hits in late spring after the plants begin growing. The new, tender growth is easily damaged or even killed, as it has not had time to fully establish. A hard frost early in fall can also cause damage, as the plants have not had time to go into a dormant state in preparation for the cold weather. Frost damage also can happen in winter when temperatures drop below the level to which a plant is adapted.
Watering deeply before a hard frost can help protect plants from frost damage, and keeping plants well watered in general also helps to prevent regular frost damage from occurring. The plant leaves store moisture, but when they are covered with frost, moisture is drawn out of the leaves. A well-watered plant experiences less general stress than a drought stressed plant, making it better able to adjust to the cold weather.
Frost-tender plants can be planted in protected areas where winter temperatures are felt less severely. A south-facing wall and a spot that is protected from winter winds can help prevent frost damage. Likewise, a spot that gets full sun will warm up more quickly during cold weather to help prevent frost damage to plants. An alternative method to protect plants from frost damage is to plant them in containers and overwinter them indoors.
Mulch also can help to regulate soil temperature, but it has to be applied before the cold weather sets in to be effective. Once the ground is already frozen, mulch prevents the soil from warming back up. Mulch should be spread 2 to 4 inches (about 5 to 10 cm) deep in fall — before the first frost — to protect plants from frost damage.
Home and garden centers also sell cloth wrapping material that can be used to protect trees and shrubs. Wrapping a frost-sensitive tree trunk with insulating cloth material can help prevent damage. Another method used to protect plants from frost is to drape the entire canopy with insulating material.
