Arborvitae are popular evergreen shrubs and trees, valued for their dense foliage and ability to form privacy screens. Understanding how these resilient plants respond to colder months is key to maintaining their health and appearance.
Arborvitae Winter Dormancy
Arborvitae do not actively grow in winter; instead, they enter a natural period of dormancy. This survival mechanism allows plants in cold climates to endure harsh conditions. During dormancy, metabolic activity slows significantly, conserving energy when resources like warmth and liquid water are scarce. This process is triggered by environmental cues such as shorter daylight hours and cooler temperatures.
Plant hormones signal this shift, reducing photosynthesis and respiration. While growth ceases, energy consumption continues in the roots and stems to maintain essential functions. This dormant state protects the plant’s tissues from freezing, allowing them to survive winter and resume growth when favorable conditions return in spring.
Winter Appearance and Common Issues
Arborvitae may exhibit appearance changes in winter, some of which are normal adaptations. Foliage of certain arborvitae varieties commonly develops a bronze, yellow-green, or brown tint in colder weather. This “winter bronzing” is a natural response to low temperatures, winds, and sunlight, causing mild desiccation and revealing underlying colors. The extent of bronzing can depend on the specific cultivar and how cold the area gets.
Beyond natural color changes, arborvitae face several issues due to winter conditions. Winter burn, or desiccation, occurs when cold winds and frozen ground prevent the plant from drawing water, leading to browning and drying of foliage, especially on exposed sides. Heavy snow and ice accumulation also pose a threat; their weight can cause branches to bend, splay, or break. Columnar arborvitae, with their upright shape, are particularly susceptible to physical damage.
Essential Winter Care
Appropriate care before and during winter can significantly protect arborvitae. Thorough watering in late fall before the ground freezes ensures roots have sufficient moisture for the dormant season, helping prevent desiccation and winter burn. Even during winter, if temperatures rise above freezing and the soil is dry, supplemental watering benefits the plant.
Applying a 2-4 inch layer of organic mulch around the base helps retain soil moisture and insulates roots from extreme temperature fluctuations. Keep mulch a few inches away from the trunk to prevent rot. For young or exposed plants, especially in windy areas, wrapping them loosely with burlap or erecting burlap screens protects from harsh winds and sunscald, reducing winter burn.
If heavy snow accumulates on branches, gently brush it off with an upward motion using a broom to prevent breakage. Avoid shaking the plant or attempting to remove ice, as this can cause more damage to brittle branches. Lastly, avoid using de-icing salts near arborvitae, as salt spray can damage foliage and bark.