How do I prevent desiccation injury to my yews and boxwoods?
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/foliage is referred to as desiccation injury or winter burn. While desiccation injury occurs during the winter months, damaged needles/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 2 or 3 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.