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- Winter burn is most common for evergreens and semi-evergreens in cold climates.
- Reduce winter damage by planting evergreens that are hardy in your zone and watering well.
- Wrap evergreens in burlap or use anti-transpirant spray to minimize winter burn.
Winter burn is a common issue for evergreens in cold climates. Although primarily a cosmetic issue, this type of damage can be fatal to plants if severe enough. Foliage starts to turn brown along branch tips and eventually progresses toward the center of the plant, causing branches, and sometimes the entire plant, to die. Here’s why winter burn happens, which plants are most vulnerable, and how to protect your evergreens from damage.
Plants Affected by Winter Burn
Also known as winter desiccation, winter burn affects both evergreens and semi-evergreens. These plants never go completely dormant and therefore continue to transpire, or release moisture from their leaves year-round. This can be problematic in winter if the ground is frozen because their roots are unable to supply the plant with moisture to compensate for the transpiration.
Winter burn is problematic for broadleaf evergreens such as azalea, boxwood, holly, mahonia, and rhododendron, as well as needled evergreens such as fir, pine, spruce, and yew. Evergreens with scale-like foliage, such as arborvitae and juniper, may also suffer damage.
Plants that are marginally hardy in the climate where they are planted, or those that have been recently transplanted and therefore have shallow or inadequate root systems, are the most susceptible to winter burn.
What Causes Winter Burn
There are several causes for winter burn. One is a quick temperature drop at the end of a winter day, after the foliage on the south, southwest, or west side of a plant has been warmed by the sun. The sudden onset of freezing temperatures may damage the plants. Another cause is when an abnormally long and warm fall delays dormancy. Strong winds and below-average temperatures late in winter or early in spring as plants are coming out of dormancy may also contribute to winter burn. Another possible cause of winter burn is de-icing salts.
How to Prevent Winter Burn
When planting, use landscape plants that are hardy in your USDA Zone and place sensitive plants where they receive some protection. At the northeast or east side of a structure, where they get part shade, the plants are less exposed to strong sun during the day, followed by freezing temperatures after sunset.
The preferred time to plant evergreens is in spring or early fall, although summer will also work if you keep them well watered. Don’t plant evergreens past early October in cold climates, as there won’t be sufficient time for roots to grow and adjust before the ground freezes.
Another precaution you should take is to ensure plants don’t enter winter with a moisture deficit. This can happen if the fall has been dry or a plant does not get the full precipitation because it is under the eaves of a house or garage. To prep evergreens for winter, irrigate them with 1 to 2 inches of water weekly until the ground freezes.
Additionally, spread 2 to 3 inches of mulch around at the base up to the dripline (the outer extent of the canopy), while keeping the mulch several inches away from the trunk. Mulch reduces soil moisture loss and extends the period of time roots can continue to access moisture before the ground freezes. It also helps prevent soil heaving in freeze-thaw cycles, which can damage roots and stress plants.
How to Shield Plants Against Winter Burn
Sensitive evergreens or those growing in sunny, windy, exposed spots benefit from the protection of a barrier. Surround the plant with 4 or 5 stakes positioned about 2 feet outside the dripline, then attach burlap to the stakes. Leave the top open rather than filling it with leaves, which could create an inviting home for bark-gnawing rodents. Remove the burlap barrier in spring when temperatures remain above 28°F.
Although some gardeners wrap individual plants tightly in burlap, this is not recommended because it can collect ice and trap moisture, leading to disease problems.
Another option is to apply an anti-transpirant. This clear coating is sprayed on the tops and bottoms of foliage to slow the rate of water loss without interfering with the plant’s respiration or photosynthesis. Bear in mind that anti-transpirants tend to degrade rapidly and will therefore need to be reapplied after rain or significant snowfall.
