With a name like evergreen, a person may think this group of plants doesn’t require much care. However, broadleaf evergreens such as hollies and boxwood often experience winter damage. There are a couple of contributing factors, both of which pertain to water loss.
High winds can cause the plants to dry out. We all know how windy the winters can be. Because the weather is unpredictable, we also can experience warmer-than-normal temperatures, as well. These warmer temperatures cause the plants to give off an unusually high amount of moisture.
When this water loss occurs at times when the ground is frozen, roots cannot take up moisture to replace lost water. The result is a browning or burning of the foliage.
There are various management practices you can employ to help prevent winter damage. Make sure the plants enter the dormant season in a healthy and vigorous condition with adequate soil moisture. Check to see the center of the plant is free of dead leaves and other debris. Also, be sure to continue watering during the dry winter months. Monitor weather conditions and water during extended dry periods or about one to two times per month.
Water only when air temperatures are above 40 degrees Fahrenheit. Apply water at midday so it will have time to soak in before possible freezing at night. If you haven’t mulched the garden beds, now would be a good time to do so. Wood chips are a great choice. This will not only help with reduced water loss from the soil, but will protect the plants by preventing rapid temperature changes at the soil surface.
Boxwoods seem to be more susceptible to winter damage. Boxwoods placed in sites exposed to winter winds likely will experience more damage. A great way to help prevent this is to provide wind protection by creating a simple wind break. Use snow fences or stretch burlap between stakes or over a lattice frame set next to the boxwood. Another option is to stick pine boughs in the ground around plants to form a wind break. When planting boxwoods, avoiding exposed, windy sites is your best option.
Large boxwoods and other evergreens prone to ice damage may be protected by wrapping the outer branches with strong nylon cord. Tie the cord securely to a low branch, pressing the boughs upwards and inward; wrap cord in an upward spiral around the bush, having cords 8 inches to 10 inches apart. Have cord tight enough to prevent breakage from excess weight of snow or ice, but at the same time, not tight enough to exclude air circulation around the plant.
David Hillock is a consumer horticulturist with OSU cooperative extension.