Each spring, many homeowners discover dead, brown foliage on their evergreen plants.
Often mistaken for diseases, most of these dead areas are the result of cold damage. Even after a seemingly mild winter, evergreen plants can still be susceptible to winter desiccation injury, also known as winter burn. Although the Augusta area does not see as much winter injury as some colder parts of the country, this year will definitely be different. With temperatures dipping into the teens this fall and three of those days being below 10 degrees, cold damage will be seen this spring in your landscape.
All evergreen plants can be susceptible to winter burn, including junipers, pines, Leyland cypress, azaleas, arborvitae, hollies, rhododendrons, boxwoods, nandinas and photinias. Winter burn can occur when the plant experiences low soil moisture, freezing temperatures, and strong winds. Because evergreen plants retain their foliage throughout the winter, evergreens are continually transpiring water through their leaves or needles.
If there is low soil moisture or sub-freezing temperatures combined with heavy winds, the plant’s roots cannot adequately replace the water that is lost during this period of rapid transpiration. Dry winter winds carry water away from leaves causing them to wilt and turn brown. When the water usage exceeds available water, the needles, leaves, and twigs dry out and die. Foliage often appears brown or bleached. The appearance of the foliage is often mistaken for insect or disease damage. Often seen on evergreens like azaleas, new blooms will appear brown and shriveled. If all the blooms on a plant are dead, then the damage is likely due to environmental causes rather than plant disease organisms. Of course, winter injury is not limited to evergreen plants. Deciduous plants are also susceptible to winter damage.
Regardless of the type of winter injury, it is often beneficial to wait until mid-spring to assess the damage. The damage is often not nearly as bad as it initially looked; new growth may come out of tissue that appeared dead. Some evergreens, like hollies, may eventually produce enough new leaves to fill in the areas lost to winter damage. Do not prune frost-damaged woody growth until the plant begins growing in the spring. Pruning too early might stimulate new growth, which would be vulnerable to late frosts. After new growth starts in the spring, prune out dead wood. Be sure to prune dead twigs and branches one inch from live tissue, or remove the entire branch to the branch collar.
The pruning techniques will depend on the damage to the plant. Pruning also helps to reduce the risk of plant disease organisms infecting the dead branches. Mid to late April, fertilize the injured plants early. This will help to fill in the voids and stimulate new growth. Irrigating the injured plants throughout the season will also help prevent future winter burn. Occasional deep watering, even during the winter months, will help ensure adequate water is available for your plants year-round. Another good practice is maintaining a 3-inch layer of mulch to help retain soil moisture.