AMES, Iowa — Horticulture specialists with Iowa State University Extension and Outreach have advice on how to maintain plants during the winter, including how to protect trees and shrubs from salt damage. Even though it may not seem necessary to care for plants during winter, it is key to ensuring beautiful yards and gardens in the spring. To have additional yard and garden questions answered contact the Iowa State University Hortline at firstname.lastname@example.org or 515-294-3108.
Homeowners can minimize salt damage by using deicing salts prudently. Before applying salt, wait until the precipitation has ended and remove as much of the ice and snow as possible. Use deicing salts at rates sufficient to loosen ice and snow from driveways and sidewalks, then remove the loosened ice and snow with a shovel (deicing salts need to be applied at much higher rates to completely melt ice and snow). Mix salt with abrasive materials, such as sand or kitty litter. Fifty pounds of sand mixed with one pound of salt works effectively. Avoid piling salt-laden snow and ice around trees and shrubs.
While the amount of salt applied to major roadways cannot be controlled, steps can be taken to minimize damage. As soon as the ground thaws in early spring, heavily water areas where salt accumulates over winter. A thorough soaking should help flush the salt from the root zone of plants. If possible, alter the drainage pattern so winter run-off drains away from ornamental plants. When planting trees near major streets or highways, select salt tolerant tree species. Bur oak, northern red oak, honeylocust, northern catalpa, Kentucky coffeetree, horse chestnut, mugo pine and eastern red-cedar are salt tolerant tree species.
The weight of heavy, wet snow can cause considerable damage to small trees and shrubs. In late fall, multi-stemmed evergreens, such as arborvitae, can be wrapped with twine or rope to prevent damage from heavy snows. When heavy, wet snow accumulates on small trees and shrubs gently shake the snow from their branches or carefully brush off the snow with a broom. When clearing driveways and sidewalks, do not throw heavy, wet snow onto small trees or shrubs. Also, avoid dumping snow onto small trees and shrubs when raking snow off roofs.
The most effective way to prevent rabbit damage to trees and shrubs in the home landscape is to place chicken wire fencing or hardware cloth around vulnerable plants. To adequately protect plants, the fencing material needs to be high enough that rabbits won’t be able to climb or reach over the fence after a heavy snow. In most cases, a fence that stands 24 to 36 inches tall should be sufficient. To prevent rabbits from crawling underneath the fencing, bury the bottom 2 or 3 inches below the ground or pin the fencing to the soil with u-shaped anchor pins. Young trees can also be protected by placing white spiral tree guards around their trunks.
After a heavy snow, check protected plants to make sure rabbits aren’t able to reach or climb over the fencing or tree guards. If necessary, remove some of the snow to keep rabbits from reaching the trees or shrubs.
Narrow and broadleaf evergreens lose considerable amounts of moisture through their leaves or needles, buds and stems during the winter months. The loss of water is mainly due to strong winds and sun. Once the ground freezes, however, plant roots are no longer able to absorb water. Plant foliage that loses a large amount of moisture may eventually dry out, turn brown and die. The damage to the needles or foliage is referred to as desiccation injury or winter burn. While desiccation injury occurs during the winter months, damaged needles or foliage often retain their green color until late winter or early spring.
To prevent desiccation injury, deeply water susceptible narrow and broadleaf evergreens in fall if the soil is dry. Continue watering on a regular basis until the ground freezes in winter. Watering is especially important to evergreens planted in the last two or three years. Moisture loss can be reduced by erecting a shield or screen to deflect drying winds or shade plants in winter. A simple screen can be constructed with wooden posts and burlap. Applications of an anti-desiccant to susceptible evergreens may also be helpful.