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Unseasonable cold snap could trigger ‘spiral of decline’ for Greater Victoria trees

Trees need help to overcome heat dome, drought, record rainfall, arctic cold

Pink blossoms popping in February are hailed as a sign of spring in Victoria. But those recent warmer temperatures fooled the pretty ornamental trees before temperatures this week dipped below freezing, which can be detrimental to those non-native species.

The region boasts many introduced trees, such as flowering plum and cherry trees, says arborist Dan Sharp, and they’re just not well adapted to the arctic outflow winds seen in Greater Victoria the week after Family Day.

“Everyone’s thinking it’s spring, including the trees, and that can do a lot of damage to them,” said Sharp, district manager for Davey Tree in Victoria.

Warm temperatures induce many trees to bud and even bloom, which means the sap starts to run. A sudden drop in temperature causes that moisture to freeze and the resulting ice crystals can be damaging.

READ ALSO: Arctic outflow leads to new record for peak electricity demand

Modified arctic air caused those colder than normal temperatures, according to Derek Lee, a meteorologist with Environment and Climate Change Canada. This time of year, Greater Victoria is accustomed to daytime highs around 9 C with lows of 2 C overnight.

The unseasonable dip in temperature was the latest challenge for plant life in the last nine months.

Trees not properly irrigated likely suffered during the June 2021 heat dome that set temperature records across B.C. It was followed by a summer of drought on Vancouver Island and November atmospheric rivers with record-breaking rainfall that can starve roots of oxygen.

“All of these things wrap up together and they start to lead to a tree that has low defence mechanisms,” Sharp said. It leaves a tree challenged in fighting off things such as fungus and insect infestations. “We call that the spiral of decline. It’s really important to interrupt that and ensure we’re helping trees to manage each of the stresses as they come up.”

RELATED: Atmospheric river behind record rain and flooding in Greater Victoria

The unseasonable cold is among the hardest to manage and the best is to prepare in advance. Make sure there’s a good layer of compost or mulch as an insulating blanket to keep the cold from penetrating deep and damaging the roots, Sharp said. Smaller trees and shrubs can be wrapped in burlap. Some local citrus growers wrap their trees in incandescent Christmas lights to combat the cold.

While preparation is key, and the cold snap is expected to end Friday, it’s never too late to add mulch.

“Mulching around the base of a tree can only do good things,” Sharp said. It still adds insulation from the cold, and from extreme heat and adds sponginess to help retain moisture during drought.

Signs of frost damage include darkened or curling twig tips and blossoms browning and falling early. That’s the time to bring in an expert, Sharp said.

READ ALSO: Future Greater Victoria droughts could be worse than any on record

After the 40 per cent chance of snow flurries overnight and early Thursday (Feb. 24), Lee said things should return to more normal temperatures this weekend. Sunny skies are expected by Friday with warmth and moisture from the Pacific Ocean moving in to return the 8 or 9 C daytime highs. “That returns us to a normal trend we would expect for the end of February. … In general, this month has been pretty nice to us,” Lee said.

Rain will likely return next week.

Though it’s tough to predict longer-term, meteorologists are generally predicting a La Nina year, Lee noted.

That could mean more cold nights for March and April.

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Christine van Reeuwyk

About the Author: Christine van Reeuwyk

Longtime journalist with the Greater Victoria news team.
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