Cottage Q&A: What causes “winter burn” in trees?

An evergreen shrub suffering from winter burn, with brown foliage By Suzanne Tucker/Shutterstock

The needles on some of my evergreens have turned brown. My neighbour at the cottage told me that she thinks it’s from winter burn. Could she be correct? Will the trees recover?—Linda Kerry, via email

Without seeing the trees, it’s impossible to know for sure—tree foliage can turn brown for many reasons. But your neighbour could be right.

“Winter burn occurs when a tree loses more water through its leaves than it can absorb from the frozen ground,” says Ryan Statham, the district manager at the Strathroy, Ont., office of Davey Tree Expert Company. There are multiple possible symptoms to look for, including brown, dry foliage; discoloured, damaged, or cracked bark; and in the spring, die back at the tips of the branches, with no new growth.

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The severity of winter burn is—at least in part—a function of the weather conditions the tree experiences through the winter. Cold, dry air and high winds cause trees to lose water through their leaves—it’s called “transpiration,” says Statham. Other factors, such as a lack of snow cover to insulate the tree roots, or sudden temperature changes—a rapid thaw followed by a sudden freeze—also put trees and shrubs at risk for losing moisture without being able to replace it.

Happily, a tree in good health can recover from winter burn on its own. (Winter burn is more destructive to a tree that’s already stressed because of other factors—pests, for example.) But if you’re concerned for your trees, and you can get up to the cottage during a warm spell, “water them deeply,” says Statham. Apply mulch to the base of the trees to insulate their roots. Come spring, prune damaged branches. This will encourage the trees to produce more healthy growth, he explains.

Cottage Q&A: Preventative tree maintenance

As is usually the case with tree problems, “prevention is the best measure when it comes to winter burn,” says Statham. Trees that are directly exposed to wind are most vulnerable. Water thoroughly in the fall and apply three to four inches of mulch at the tree’s base. You could also treat the tree’s foliage with an anti-desiccant spray, says Statham. It acts as a waxy coating and helps to seal in moisture.

Got a question for Cottage Q&A? Send it to answers@cottagelife.com.

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