Protecting your trees in winter
Our city’s geographic location can bring extreme cold, dry Chinook winds, and freezing rain – sometimes all on the same day.
Here’s some information and tips on keeping your trees healthy and happy over winter.
Winter temperatures impact trees in a few ways: the dry cold can desiccate them, damage bark, and injure or kill branches, flower buds, and roots. Trees outside of our hardiness zone may not make it through winter, and native trees can be impacted temperatures are very harsh, or if they’re already stressed.
- Plant trees adapted for our climate: native species, or ones that grow in the 3a – 4a hardiness zone will do best.
- Mulch your trees’ roots to help insulate against drying winds and freezing temperatures.
- Keep your trees healthy before winter; healthy trees can handle winter more easily.
Calgary gets a lot of sun, especially during our winters. This can sometimes cause sun scald, which is sun-damage to a tree’s bark. During the day, sun heats up the tree bark, “waking” the tree to come out of dormancy. But when the sun is blocked or sets, the bark temperature drops quickly, causing the active bark tissue to freeze and die.
Recognize sun scald by patches of elongated, sunken, dried, or cracked areas of dead bark, usually on the south or southwest side of a tree.
Trees at risk of sun scald:
- Young, newly planted, or thin-barked trees
- Coniferous trees that have been pruned to raise or “skirt” the lower branches
- Trees transplanted from a shady to a sunny location
- Wrap south-facing tree trunks with a commercial tree wrap, plastic tree guards, or light-colored material. This reflects the sun and keeps bark at a more constant temperature.
Calgary has experienced the tree-damage caused by snow and ice, most recently during Snowtember in 2014. Heavy snow and ice bend and break branches.
- Prevention: proper pruning, for sound structure and to remove weak branch attachments, will reduce snow and ice damage.
- If safe, during larger snow storms, shake snow off trees to reduce the weight load.
Salt and deicing chemicals can hurt trees by injuring roots and being absorbed by the tree.
- Avoid planting trees in areas where salt/chemicals are heavily used, including where runoff collects.
- Shovel sidewalk snow away from tree trunks.
- If possible, limit use of salt or de-icers on sidewalks, and shovel more frequently.
Mice, rabbits, and deer can damage trees in the winter, by feeding on the tender twigs, bark, and foliage. They can girdle trees by removing all the bark on the base of the trunk area. Some areas in Calgary may also see deer causing injury and breakage by rubbing their antlers on trees during the fall.
- Shovel snow away from tree trunks; the snow provides a step-up for animals to graze on bark.
- Wire-wrap trunks in winter to prevent animals making a meal of the bark.
They bring colour and festivities to our winter season, and with a few easy steps, holiday lights can be enjoyed with no damage to your trees.
- Don’t overburden the frozen branches with too much weight, and remember to account for wind.
- During the months of October - February, you may hang lights in a public tree, so long as you're not violating any regulations around the location of electrical cords or creating a safety hazard.
- Using a ladder? Ensure it’s stable, and on a flat, level surface. Move your ladder to reach branches, instead of leaning off it.
- When branches are cold or frozen, they can be damaged easily or even snap off. Be gentle and protect the buds on your trees for next spring.
- Don’t wind lights too tight on branches, and don’t leave them up past the holidays as they’ll strangle the trees over time.
- When removing decorations and lights, remember – last up, first off.