Last week, the temperature dipped to -51C, the lowest I’ve ever experienced. And that was in the morning. Mind you, wind chill was factored in but even still it was frigging cold. We’re in the small, fabulous town of Fernie, British Columbia–our home for half the year every winter. Fernie is a ski town. We have a large ski resort that, I’m proud to point out, is often voted “best of” by skiing enthusiasts for things like powder conditions, apres-ski options and general awesomeness. But during our freakishly cold spell, the entire resort was shut down. When the temps are in the minus 40s to minus 50s, frostbite can occur in minutes. If you got into trouble on the hill while skiing, you could die.

A groomed cross-country ski trail just minutes from our home in Fernie, B.C.

Groans and squeaks

Fernie offers all kinds of winter activities besides skiing, of course. One of my favourites is simply taking a walk in the forest. We’re lucky to have so many trails nearby that you can walk from the heart of downtown Fernie (all of five blocks long) and within two minutes be enfolded in a wintery silence buffered by a mixed forest of evergreens, deciduous trees and tall shrubs. Well, almost silent. But it’s not just me who’s doing the groaning, coughing and squeaking.

I’ll stop along the trail to listen to that beautiful silence. Stopping is crucial because my every step makes a squeak. Water freezes at 0 degrees Celsius but the temperature only has to drop to about -10C to stop the friction of your boots from melting the snow. Instead, the crushing of the snow crystals makes a squeaking sound. When the mercury has dropped below -40C, the squeaking sounds can be ridiculously loud.

If there’s any kind of breeze, that’s when I can hear the trees sing their winter songs. Or maybe they’re more like laments. Rasping groans as two large tree trunks rub against one another. A sharp cough as a branch snaps from under the weight of the snow.

Gun-shot cracks

In late afternoon, the sun sets behind the craggy ridge of the Lizard Range. That’s when I stop for a moment, listening for that rare, shocking “CRACK” sound. Sometimes it can be as loud as a gun shot. That’s the making of a frost crack. On a clear winter day, the sun can warm the bark and inner wood of a tree. Then, as the sun sets, the temperature drops dramatically. The bark shrinks but the inner wood will take longer to cool and contract. This inequality of actions results in the bark and some of the inner wood directly below the affected bark suddenly and forcefully splitting with a bang. The result is usually a long, deep, vertical gash in the tree’s trunk or, less commonly, along a branch.

Tending to a winter-wounded tree

You don’t have to live in a small mountain town to have a tree that suffers a temperature-related crack. All it takes are sub-zero temperatures and a tree that’s susceptible to this problem. Maples, lindens and walnut trees seem to be particularly at risk.

What should you do if your tree suffers a crack? Simply keep an eye on it. Trees will begin the process of self-healing automatically and many of these cracks close up over time. They can be an entry point for pests of the insect or fungal persuasion but that’s not a fait accompli. If you have a wounded tree, the best you can do is give the tree a little extra love, ensuring the tree is well-watered and perhaps sprinkling around a little fertilizer if you think the tree needs a little help.

For a good article on frost cracks, check out Michigan State University’s article on Frost Cracks In Trees.