Calgary arborists concerned about city's trees as dryness continues, water restrictions loom

As Calgary continues to experience dry conditions, some local arborists are concerned about the health of the city's trees, especially as tough outdoor water restrictions are set to begin at the end of the month.

According to the Canadian Drought Monitor, Calgary is under "abnormally dry" conditions. Alberta's drought map says the Bow River Basin, which covers Calgary, is under Stage 3 conditions that include monitoring water levels.

Matthew Davis, the owner of Adair Tree Care, said that trees in places where they aren't usually watered by people, like local parks, are "really starting to show the signs of a number of years of less than ideal moisture conditions."

Those signs can include yellowing leaves or whole branches starting to lose leaves, Davis said, adding that dry soil conditions on the surface can mean that "it's probably dry lower down."

Davis pointed to poplar trees — which the city says are the "backbone" of Calgary's urban forest — and said "they seem to be struggling on a widespread basis throughout the city."

When trees struggle under drought conditions, Davis said they become more susceptible to insects and disease.

Kevin Lee, a longtime arborist and owner of KRL Tree Service, said he's always worried about Calgary's trees since the city isn't in a forest zone.

Not only that, but Lee said Calgary is in "year-four of a pretty serious drought cycle in a naturally dry place," which exacerbates the current problem.

In Lee's view, the only urban trees that are doing well are ones where people understand the challenges and are adding a lot of additional water. "So yeah, I am very concerned about Calgary's trees," he said.

"A tree has an incredible amount of water requirements and can just not live and function without adequate water. It begins there."

Tough outdoor water restrictions looming

The City of Calgary is planning to move to Stage 4 outdoor water restrictions on Aug. 26. Under those rules, no water use is permitted outside. Residents and businesses across Calgary will also be asked to conserve water use.

Lee said that although Calgary has had cooler days recently, he highly suggests people water their trees before the restrictions come into effect.

Davis also gave the same advice and said people should take advantage of the current, more lenient outdoor water restrictions to prepare as much as they can.

He said it's "not ideal" the tough restrictions are going back into place since "most of us would recommend watering your trees into the fall before they freeze up or the ground freezes up."

In a statement to CBC News, the City of Calgary said "one method of protecting trees during drought conditions is to water trees and surrounding soil ahead of time, and ensure there is mulch over the root zone."

"As cooler conditions and shorter days set in, there will be less drying out of the soul compared with earlier in the summer," the statement also said.

Davis said that when people water trees, they should try to get the water as deep into the soil as they can so the roots grow deeper. 

That makes the tree more resistant to future drought conditions, since the roots can capture water deeper underground that is slower to evaporate, he added.

City officials have said the Stage 4 restrictions are expected to last until late September.