Evergreens add so much to the landscape. This is especially true in winter, when there’s little other color. Whether needled evergreens like pine or spruce or broadleaf ones such as azaleas, their green, blue, silver or bronze foliage really comes into its own when the temperatures drop.
There’s one color though, that gardeners don’t want to see on their evergreens, and that’s orange. With the exception of a few cultivars with foliage bred to turn an appealing orangey-red in the cold, orange foliage on an evergreen is likely due to a condition called winter burn.
With winter burn the needles on evergreens turn a bright orange-brown. On broad leaved evergreens the browning starts on the edges of the leaves and buds and moves inward. This color is because the foliage has dried out and died. It’s a relatively common occurrence, particularly in the colder areas of the U.S. Often it is not noticeable until spring, when the plant breaks dormancy.
Winter burn can be caused by a few factors, but all the reasons boil down to a lack of moisture: the leaves on that part of the plant lost water faster than the roots could replace it. It most commonly occurs on the south and west sides of the plant where the sun is strongest.
Reasons include harsh, dry winter winds dehydrating needles or leaves, or a transplant that didn’t have a strong root system or get enough water before the soil froze. An unusually cold winter, or a series of warm early spring days that encourage growth followed by a sharp drop in temperature can cause winter burn. A plant exposed to too much deicing salt, or any plant that is planted in a colder zone or on the cusp of hardiness, i.e. a zone 6 plant in zone 5, is vulnerable to winter burn, even if it would be fine in its proper zone.
Winter burned needles or leaves will not recover and should be pruned out. New growth will likely replace it, and the plant will be fine. Wait until spring to prune. If it’s hard to tell whether the affected part is still alive, scratch away a bit of the bark. If it’s green underneath, the branch is alive. If it’s dry and brown, it’s likely dead. When the burn is extensive the entire plant may die, or be disfigured to the point where it is no longer an asset in the landscape and must be removed.
Evergreen species susceptible to winter burn include:
There are evergreen species supposedly less susceptible to winter burn, such as Sitka spruce or blue spruce, but any plant can suffer from winter burn if it is water stressed and conditions are right.
Avoiding winter burn comes down to two things: prevention and plant care.
Ways to prevent winter burn include siting vulnerable evergreens out of strong winds, and timing the planting of new trees and shrubs for early spring or later in summer to be sure the soil is warm, and there is enough time for their root systems to recover before the ground freezes.
Stop pruning or fertilizing evergreens before late summer, so the plant doesn’t push out new growth that can’t harden off before temperatures drop. If a plant requires part shade, don’t plant it in full sun, and choose plants that are known to be winter hardy in your zone, especially if they will be sited in an exposed, windy area.
Care includes consistently watering newly installed trees or shrubs– or any evergreen suffering from stress – in fall and even in winter on warm days. This is especially important for plants under eaves, where parts of the plant aren’t exposed to rainfall. Mulch well (2-3” deep around the dripline of the plant, and 3” away from the trunk) with a loose mulch that allows water to percolate through.
Stake and wrap the most vulnerable plants (not tightly!) with burlap or other fabric that breathes, leaving the top open for moisture to evaporate. Anti-desiccant sprays have their defenders who believe they work, and critics who think they don’t. They do need to be reapplied through the winter.
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By Delilah Onofrey, Suntory Flowers
Photographs courtesy of Suntory Flowers
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