Mirage Landscape design of Calgary has been serving the city for three generations. Throughout the winter and into the spring we see all kinds winter damage to trees and other plants while we perform snow removal services, and want you to know when you should be worried about your trees. Every tree and shrub is precious in Calgary, and we want you to be able to enjoy them for many years to come.
The Killer Wind of Calgary’s Winter Weather
By far the most challenging weather that plants face in Calgary is the highly variable freeze/thaw cycles we have due to the winter wind patterns here. Being in the Chinook wind belt of southern Alberta, just east of the large and natural wind funnel of the Bow River valley, creates some extreme temperature swings. We go from having bitterly cold arctic air masses hanging over us to seeing warm and dry winds come off the eastern slope of the Rockies.
These Chinook winds are really the remains of moisture laden systems that have pushed themselves “dry” by scaling the windward side of the Canadian Rockies. The moisture is wrung out of these systems by dumping snow on the western slopes of the mountains, and losing mass, accelerate up and over to the leeward, or “rain shadowed” side of the range, where they pick up speed and generally blow south by southeast.
A dry warm wind that drives right through the cold air masses from the north is not only the wind that melts snow away into enormous puddles, chaps your lips and causes headaches for some, it desiccates your plants by prematurely forcing them out of dormancy.
Plants damaged by Chinook winds are said to be suffering from “tip kill,” or “die back.” Literally, your plants being damaged this way are being dehydrated through an increase in water loss while the roots remain frozen, unable to draw in replacement water.
Signs of tip kill include dry twigs, discoloured evergreen needles, or even the death of entire smaller plants. The damage is permanent but can be mitigated with pruning. The only effective preventative measures are to create artificial windbreaks where necessary, or if lower laying plants are most affected, to provide plenty of mulch cover to protect the heartier parts of the plant or shrub.
The Chinook wind can also cause “false spring,” where the sustained temperatures are warm enough to break dormancy, triggering sap flow and premature new growth. Then when the winds fail, sensitive plant tissues are killed or severely damaged by the renewed cold.
Sun Scald—The Other False Spring
Even when the Chinook winds aren’t present and snow is on the ground, you have to be on the lookout for sun scald. Sun scald particularly afflicts south facing trees and shrubs. What happens is that on clear and cold sunny days the reflected light off of the snow warms the exterior of the tree or shrub, thawing its tissues. The sun then sets, and the thawed spot refreezes once again. Eventually, this freeze/thaw cycle opens a crack in the bark, exposing the inner layers and damaging the tree. The crack will not usually be fatal to the tree, but come spring you should clean the wound out to ensure that it doesn’t become an insect infestation point.
If you see a vertical crack opening up on one of your trees, it’s never too late to apply a tree wrap to it. The wrap will prevent the sun from further damaging the tree. Remove it come spring.
Trees and Shrubs? Dinner Time!
Just a quick reminder that not all winter hazards to your trees and shrubs are directly from the weather. Deer and other non-hibernating animals, such as rabbits, will readily attack tree and shrub bark as a food source. If they can gain access to yours, it is possible to protect vulnerable plantings with wire fencing around the trunk.
Salting The Earth—Old World Destruction
When the Romans finally defeated the Carthaginians they salted the fields around the defeated city to ensure nothing would grow there again. While not quite on the same scale, you could be killing off parts of your own landscaping by over applying de-icing products to your walks and driveway or by not being observant as to where the run-off flows.
Let Mirage Handle It
If you suspect that your plants are being damaged by the weather, call us to inspect and control the damage. Call us for a free quote.