Causes of Splitting Arborvitae
When snow accumulates on an arborvitae, the branches can bend and pull away from the center of the plant. This damage occurs in many arborvitae varieties, such as 15-foot-tall and 4-foot-wide “Emerald Green” (Thuja occidentalis “Emerald Green”), which grows in USDA zones 3 through 7, and 15-foot-tall and 2-foot-wide “Degroot’s Spire” (Thuja occidentalis “Degroots Spire”), which is hardy in USDA zones 2 through 8. After heavy snowfall, damaged branches can break and fall, and cause stems to split.
Repairing Snow-Damaged Arborvitae
You can use a broom to brush snow from arborvitae branches with an upward sweeping motion. When new growth begins in the spring, prune broken and dead branches to 1/4 inch above a live bud, or to the nearest live branch collar. Do not remove live branches that are green under the bark layer. To avoid spreading disease, soak the pruning tool in full-strength household disinfectant for five minutes and air dry before pruning the next tree; disinfect between cuts if a history of disease exists. You can tie bent branches back in place with rope so that they will resume normal growth. It is important to remove the rope after two years so that the tree does not grow around the rope and develop girdling, which can kill the tree. You may have to hire a tree care professional to remove severely split arborvitae, which can have root balls that are 4 feet wide and 2 feet deep.
Preventing Snow Damage
To prevent snow damage and splitting, you can wrap or tie your arborvitae branches to keep the top branches together during the winter. Before the first snow, wrap the tree in burlap, or tie the branches together with rope or bungee cords, as recommended by Michigan State University Extension. When the chance of snow is gone, remove the burlap or rope. To prevent damage to trees from melting and sliding snow and ice, plant arborvitaes away from roof overhangs.
Some types of arborvitae resist breakage and splitting from heavy snow accumulation, notes Olbrich Botanical Gardens. For example, “Hetz Wintergreen” (Thuja occidentalis “Wintergreen”) grows up to 25 feet high and 6 feet wide, and thrives in USDA zones 4 through 9. Hardy in USDA zones 3 through 7 “Siena Sunset” is a compact variety that grows up to 2 feet high and 2 1/2 feet wide. Besides resisting snow damage, “Siena Sunset” also resists deer feeding, which is another winter stress. Another split-resistant species is large, pyramid-shaped western or giant arborvitae (Thuja plicata), which grows up to 70 feet high and 25 feet wide and is hardy in USDA zones 6 through 8.