Frost during the spring can potentially cause damage on some plants, especially if the frost occurs after a long, warm period. During cold nights, the ground radiates heat. Fortunately, this heat can be used and trapped to help protect your plants from frost. This form of frost protection can be accomplished in many ways so the average home gardener can choose which way suits her needs and ability. Remove the frost protection during the daytime if frost is not a danger and replace it as needed.
Place a cardboard box over your plants. The bottom should be open and the top and sides should be closed. This works well on smaller plants.
Set a patio or lawn chair over your plant and drape a sheet, blanket, piece of burlap or frost cover over it. Ideally, the cover should touch the ground on all sides.
Drape a piece of burlap, sheet, blanket or frost cover directly over your plants. The cover should touch the ground on all sides. Some plants, like shrubs and trees, can withstand the weight of the cover, but smaller plants may need a frame from which to hang the material.
Build a simple frame for the cover to hang on. Stake in at least four posts around the plant slightly wider than the largest branches. In addition, the posts should be about 6 to 12 inches taller than the plant to allow room for the cover to sag without damaging the plant. Larger plants may need more overhead clearance. Drape the cover over the frame. Use one that's long enough to reach the ground on all sides.
Add a light bulb under the cover. If you are experiencing an unusually cold spring, use an outdoor lamp with a 100-watt bulb to warm larger plants, usually trees. Place the bulb near the bottom so the heat can radiate up. Keep the bulb away from the cover, trunk and branches. Alternatively, use outdoor Christmas lights to heat the plant.