Winter can be a tough time for landscape plants, especially those that aren’t native to this climate. Damage can include freezing, frost cracks, physical breakage, salt damage and desiccation (water loss). There are steps that can be taken to minimize these effects, though, and fall is the best time to do it.
Freezing injury and late spring frost damage are common problems on plants that are not completely hardy in northern climates. To avoid these, it is best to plant only species and cultivars known to be hardy here. For spring frosts, shading the plant may help to prevent damage—by keeping the warming rays of the sun off the plant, bud break may be delayed up to 10 days, which may be long enough to protect tender flowers and shoots. This may be practical only with smaller plants, however.
Frost cracks and sunscald can be a problem on newly-planted, thin barked trees. Damage usually occurs on the southwest side. Winter sun warms the bark during the day. Temperatures then plummet at night, causing the outer bark to cool and contract faster that the inner tissue, which causes splitting of the bark. Newly-planted species that are prone to damage can be shaded or the bark wrapped with light-colored material to reduce risk.
Physical damage from snow load can be avoided by either wrapping susceptible plants with twine or chicken wire, or covering with a constructed snow-shield. Pruning trees when they are young to eliminate weak, V-shaped branch attachments can also help reduce the likelihood of breakage.
Avoid planting species susceptible to salt damage in high-traffic areas. Otherwise, burlap or canvas screens can be constructed to protect them from salt spray.
Desiccation can occur on evergreens on bright, sunny winter days. The sun warms the foliage, and moisture is lost to the surrounding dry air. Because the ground is frozen, the roots are unable to take up moisture to replace the loss, and foliage browns and dies. Watering plants well into the fall (until the ground freezes) can help, as well as siting sensitive plants where a building, fence, or other plants will supply winter shade. A sun shield can also be constructed to provide shade.
Planting appropriate species and taking steps to avoid winter injury will ensure longer-lived, healthier plants in the landscape.