We’ve all seen it around Calgary, even if you didn’t know what you were looking at. Those unsightly brown patches on your grass, trees, and evergreens found in the spring time as the snow and ice melt is what’s called “winter burn” or “snow scald”.
This unfortunate browning of foliage is often caused by extreme cold temperatures through the winter. For us in Calgary, it’s quite likely it occurred in February of this year, when we had that uncharacteristically extreme cold month (the coldest February we’ve had in 20 YEARS!), but many factors can contribute to snow scald.
Plants with poorly developed root systems or shallow root systems are more susceptible to snow scald. This would include recent transplants of native plants, as well as other foliage not native to our area and our climate. Because their root systems are not quite established, they aren’t able to efficiently take in enough water to keep them healthy through the winter.
Another factor that contributes to snow scald are warm temperatures in the fall that trick the plants into not preparing properly for the cold months. This leaves them more susceptible to getting burned by the cold because they have delayed the dormancy needed to survive the winter.
Similar cold injury can occur mid-winter when temperatures drop sharply in the evening, causing foliage that warmed up during the day to rapidly freeze. In addition, on sunny winter days, foliage that faces the sun can begin to transpire and because the ground is frozen, plant roots cannot take up water and replace the water that has been lost from the foliage. As a result, foliage dries and browns. Foliage that’s protected under the snow or facing away from the sun and direct winds is usually not damaged. Strong winter winds on unprotected foliage can lead to additional water loss making winter burn more severe.
How we revive your plants after snow scald:
-Check for signs of life under the brown areas
-Prune dead, brown, or damaged foliage from your evergreens
-Remove the entire tree, shrub, or other foliage if recovery is impossible
-Replace with a more appropriate/resilient shrub or tree
Preventing snow scald from happening in the future
The easiest way to prevent snow scald from occurring is to plant the proper foliage for our seasons and climate. It’s recommended that plants that are cold-hardy and well adapted to our area are used. We always plant evergreens at a time of year that allows them to properly prepare themselves for the cold months.
Other simple ways to prevent snow scald
-protect plants with burlap, canvas, or snow fences
-avoid fertilizing late summer, which stimulates new foliage more susceptible to snow scald
-water plants properly (well hydrated plants are less prone to damage)
-mulch your evergreens properly to insulate roots from severe temperature fluctuations
Example of snow scald on Alberta Spruce. (Taken from Wisconsin Horticulture).
Example of snow scald on boxwood shrubs. (Taken from Katy Elliot).
Inspiration Taken From:
Global News. (2019, Feb). Calgary’s cold February the worst in 828 months: Environment Canada. Retrieved from Global News: https://globalnews.ca/news/5012846/cold-calgary-february-worst-environment-canada/
Katy Elliot. (2019). Oh No My Boxwoods. Retrieved from Katy Elliot: http://www.katyelliott.com/blog/2011/04/oh-no-my-boxwoods.html
Wisconsin Horticulture. (n.d.). Winter Burn. Retrieved from Wisconsin Horticulture: https://hort.extension.wisc.edu/articles/winter-burn/