Thermal Blankets for Shrubs

Thermal Blanket Materials

• Thermal blankets come in a variety of materials. Some are made from fleece and may require additional plastic placed over the top to act as a water barrier. The most common material is polypropylene foam, used either by itself, or laminated to a material -- such as polyethylene film -- that assists in controlling damaging ultraviolet rays. Read the directions of any thermal blanket used, and follow them; failure to do so can result in killing the shrub. In warmer weather, store a thermal blanket in a cool, dark area; with proper care, blankets can last for several years before needing replacement.

Placement of a Thermal Blanket

• Unroll the thermal blanket, and brush off any snow or ice already on the shrub if necessary. Following the manufacturer's directions, toss the cover over the top of the bush, centering it; drape the sides of the blanket down the sides of the shrub. The length of the blanket should be aligned in a north-south direction for maximum sunlight exposure. To prevent the blanket from falling or blowing off, secure the ends by placing them under something heavy, such as a stone or a brick.

Advantages

• Thermal blankets are not prohibitively expensive; numerous blankets can be purchased to protect even large yards full of shrubs. And because they are designed to allow rainwater to pass through, yet -- like mulch -- trap it from evaporation, this saves on watering plants in warmer climates experiencing colder weather. Blankets can be easily removed once temperatures return to above freezing, or in the spring when the threat of frost has passed.

Disadvantages

• Covered shrubs will need to be watched closely during premature thaws to avoid damage. New growth could occur if the plant is tricked into thinking the climate is warmer than it is; once the thaw ends, the new growth can then be damaged by freezing temperatures. Air circulation is very poor; mold and mildew can cause the shrub to begin rotting beneath the blanket. And because the blanket is dark colored, a homeowner cannot just glance at the cover to see if the shrub is doing poorly; it will need to be lifted -- diligently -- to ensure the shrub is not being overheated.