Winter Injury to Evergreens
Browning of evergreen foliage at this time of year is a sign of winter injury due to low temperatures, fluctuating temperatures, and drying out. Plants in sunny, protected locations tend to warm up in winter making them more susceptible to damage from fluctuating temperatures than plants in shaded or exposed locations.
Drying out, or desiccation is another major cause of winter injury on evergreens. When the soil is frozen or very dry, plants cannot take up sufficient moisture, but they continue to lose it through their leaves. Exposure to wind and sun increases the chance of this type of injury. Winter damage normally occurs on the south or southwest and windward sides of plants, but in severe cases, the whole plant may be affected. Camellia and holly are two of the plants that we commonly see this type of damage, but winter browning can affect all evergreens. Small, shallow‑rooted plants are often injured when alternate freezing and thawing of the soil heaves the plants from firm contact with the soil and exposes the roots to drying winds. Newly planted plants that have not become fully established are particularly sensitive to heaving.
If an evergreen has suffered winter burn, wait until you begin to see active growth in late spring before doing any repair. Brown foliage is dead and will not green up, but the buds, which are more protected than the foliage, will often grow out and cover up the brown. If all the leaves fall off and no life is evident in the stems, prune back to live wood. Do a soil test and fertilize the shrubs if needed after pruning and water well throughout the growing season.
Keeping evergreens well-watered throughout the growing season and into the fall is one way to reduce winter burn. Watering during mild spells in winter when the soil is dry and not frozen also helps reduce injury. Other steps you can take to prevent winter burn are to use pine boughs to prop against plants prone to this damage or you can construct a barrier of burlap to shield plants on the south, west, or windward side of plants. If a plant has been showing injury on all sides, surround it with a barrier but leave the top open to allow for aeration and light penetration.