Each spring, 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 with a seemingly mild winter, evergreens can be susceptible to an injury known as winter burn. Although the Augusta area does not see as much winter injury as some colder parts of the country, newly transplanted plants and young evergreens experience their fair share of cold damage.
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 evergreens retain their foliage throughout the winter, they are continually transpiring water through their leaves or needles. If there is low soil moisture or subfreezing 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 such as 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 might come out of tissue that appeared dead. Some evergreens, such as hollies, might 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 can stimulate new growth that will be vulnerable to late frosts. After new growth starts in the spring, prune out dead wood. Be sure to prune out dead twigs and branches 1 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.