Trees loving this year's snowy winter, says Arboretum expert

Trees that have adapted to a Canadian winter love snow. 

And with more of a traditional cold and snowy winter this season, trees are reaping the benefits, according to Alison Morrison, manager of horticulture at the University of Guelph Arboretum.

“Our last winters have been all over the place. Certainly, getting a nice healthy layer of snow really buffers the winter conditions for trees,” Morrison said, speaking generally about trees throughout the local area. 

“The snow acts as an insulator on the earth which stabilizes the temperature of the soil. Our trees are either native and have adapted to cool winters, or they are ornamental and are bred for these conditions.”

Morrison, an Ontario Agricultural College (OAC) trained horticulturist and certified arborist, said it’s not really low temperatures that impact trees and their resilience, as much as it is the changes in temperature. 

“Trees like to set themselves up for dormancy and when we have periods of warmth, it almost confuses them,” Morrison said

“Fluctuating freeze-thaw cycles can stress trees, damaging their bark and roots.”

In winters where there are sudden long warm periods, trees can start to break dormancy. 

“They think it’s spring. We see the buds swell early and then if a late frost does happen after that, they don't have the protection that they need for the winter. So the leaves get burned and we lose our beautiful blossoms on our cherry and apple trees,” Morrison said. 

Morrison said nothing happens to a tree overnight or very quickly.

“That seed has a little timer inside of it that wants to know a healthy winter has passed and that they will have good spring conditions to grow,” Morrison said. 

“When we get those warm periods, we confuse all of our beautiful native tree seed and potentially it breaks dormancy. You will have a tender little shoot that is trying to regenerate in a forest that’s about to be hit by another bout of winter.” 

At the Arboretum, a big focus is on knowing the provenance of its trees and their seed. 

“This includes understanding the origin of where our trees and their seed developed and what regions they have adapted to,” Morrison said. 

“So, if we have modelling that predicts that we are going to have a warmer climate, and we are going to have less consistent winters, then understanding where our trees are from will help us to select a batch of trees or assist the migration of species into ranges where they can exist in a healthy way.” 

Morrison said winter offers unique opportunities to see trees in a fresh light, catching details that might often be missed in warmer months. 

The Arboretum hosts workshops and guided walks during the winter months.  

To learn more, visit the Arboretum’s education and events page for upcoming workshops on winter tree identification.

“When you learn tree identification, it’s so easy to get obsessed with the leaves. They all have distinct shapes, sizes and colours. But there are so many other components to a tree that are so distinct and easily identifiable,” she said. 

“Buds are a great way to tell the species apart. If you look at ash tree leaves, many of them might look the same in the species, but if you look at their buds, they are actually very distinct."

Morrison believes bark has a beautiful colour and texture against the winter landscape.

“It is so distinct and pleasurable to look at and so nice to take in during the winter,” she said. 

“Something about it against the white and grey landscape brings out the colour depth in bark that you don't notice in the bright greens of summer.”