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Renegade maples, unpopular poplars and other troublesome trees

Ottawa has a vibrant urban canopy, but sometimes our trees don't act the way we expect them to.

"Trees aren't just pretty objects that we put up," said Joanna Dean, an environmental historian at Carleton University, ahead of a talk last week.

"They have a life of their own, they move, they change, they grow."

As Ottawa started to urbanize, Dean told CBC Radio's Ottawa Morning, the city made an effort to bring in more trees that would provide shade and cooler air.

Some of them, however, ended up on Ottawa's bad side.

Ian Black/CBC
Ian Black/CBC

The renegade maple

Dean told Ottawa Morning about three trees that have caused trouble, the first being the Manitoba maple.

It was widely planted on city streets during the late 1800s and early 1900s, she said, because it grew quickly and provided good shade.

But then it was banned — in part because heavy snow or windy weather would cause the branches of the "brittle tree" to snap off.

"They've got some very bad habits," Dean said. "They break."

Courtney Markewich/CBC
Courtney Markewich/CBC

When it became evident that the maples were creating more trouble than they were worth, the city tried to get them off the streets.

But the Manitoba maple wouldn't go easily.

They would spring up all over the place, Dean said, and one of the locations they flourished was Parliament Hill. A study in the 1980s revealed that the Manitoba maple was crowding out all the other trees on the slopes behind Parliament.

"These were weed trees ... these were runaways, they were escapees," she said.

Though the tree is no longer banned, Dean said, it's certainly not one the city encourages planting.

Tim Propp/CBC
Tim Propp/CBC

Centennial crabapples

Another tree that's been discouraged in the city is the ornamental crabapple tree.

It was popular in the 1960s, said Dean, when Canada's Centennial Commission wanted the bright pink trees everywhere.

The city even gave 1,800 free trees to residents to plant on their property, and the National Capital Commission planted them alongside roads.

"But they turned out to be a problematic tree," Dean said. "In the fall, we have nothing but crabapples underfoot — and [that brings] wasps."

The two varieties that were so strongly promoted by the Centennial Commission are now discouraged from being planted, she added, because they're very prone to disease.

Brian Davies via Associated Press
Brian Davies via Associated Press

An unpopular poplar

A third tree that caused tensions in the city is the Lombardy poplar.

It was brought over from Italy, and given its thick canopy, it was used to line Central Park in the Glebe.

"They made a lovely cloistered park," Dean said. "You couldn't see any of the houses. It felt like you were out of the city."

But it you lived next to the park, the trees also hid your entire view.

There was one resident, Dean said, who was particularly vocal about the Lombardy poplar that stood between the park and her property — so vocal, in fact, that the tree was eventually removed.

Philippe Turgeon/CBC
Philippe Turgeon/CBC

A 'vibrant urban forest'

Looking at the history of Ottawa's troublesome trees has implications, Dean said, for how we currently think about our urban canopy.

She said it's important that we learn to live alongside trees, and also understand legitimate concerns that people have about some of them.

A lot of trees get removed, she said, because they're in someone's way.

"Until we realize how to work better with trees," Dean said, "we're not going to be very successful in creating a strong and vibrant urban forest."