Not only is the Bradford pear the stinkiest tree of spring — it's an invasive species

The Bradford pear is the ultimate Dr. Jekyll and Mr. Hyde story.

In spring, the non-native tree, originally from Asia, produces gorgeous white flowers, and in the fall, vibrantly coloured leaves.

"I would consider it an ornamental tree, so this is not a tree that going to grow to be 60, 70, 80 feet in height," said Windsor city forester Paul Giroux. "It's an important tree for the landscape who have confined planting locations."

Of the roughly 70,000 trees in Windsor, 2,300 of them are Bradford pears, which is a cultivar of the callery pear. Every year, the city adds 50-75 of them to that inventory.

The problem? Those pretty white flowers stink.

The smell of the Bradford pear has compared to rotting fish — and even bodily fluids.

So why would anyone plant such a stinky tree?

"It was brought over to North America because it was pretty hardy ... it just seems to grow in really rough conditions," explained Amber Cantell, director of programs at ReForest London, a non-profit group dedicated to planting trees in the Forest City. 

Life in the middle of a sidewalk or a road median, surrounded by concrete and asphalt is difficult — so it makes sense to plant the strongest trees there, right?

Countless cities across North America seemed to agree, and according to The Washington Post, it became the "ubiquitous street tree of America's postwar suburban expansion."

A much larger problem than smell came decades later, when the Bradford pear escaped the confines of suburbia and into the wild. A growing number of people, especially in the American south, consider the tree an invasive species.

The South Carolina Forestry Commission explained the problem on YouTube:

Giroux said this hasn't happened here yet.

"We have not seen these escape into our natural areas at this point, being said, we do not like to plant non-native trees in our parks," he said.

As a result, Windsor continue to plant about 50-75 new Bradford pears trees each year — but not in parks or natural areas. Overall, it's a small percentage of the trees added to the city's inventory.

"We need to be a little bit more tolerant to planting non-native trees, because there's nothing really native about a really hot environment that's surrounded by cement," Giroux added.

ReForest London's Amber Cantell agrees that the Bradford pear is not an aggressive invasive species in Ontario. However, she says that could change.

"The going theory is that it's the colder weather here in Canada that inhibits them a bit," she said. "We have a concern that as the climate warms, invasive species that are currently really invasive in America will start becoming really invasive here."

Reforest London places the Bradford pear on a list of trees that should not be planted in that city, going so far as to say the trees "should not be planted under any circumstances and should be removed where possible to prevent further invasion."

CBC News asked municipal forestry departments in London, Sarnia, Chatham-Kent, Detroit and Toronto if they plant the Bradford pear as a city trees.

Kat Hodgins from the City of London says about 1-2 per cent of the 6,000 trees they plant each year are Bradford pears. She notes the city is actively trying to reduce that number and is running experiments with different types of trees to find a suitable replacement for a tree that continues to be popular with developers and landscape architects.

The City of Toronto says that it does not plant the tree, and Sarnia, Chatham-Kent and Detroit did not reply.

What are the alternatives?

Cantell's personal favourite alternative to the Bradford pear is the serviceberry, a native species with white flowers that Ontario's Ministry of Natural Resources and Forestry calls "very adaptable."

"The fruit are edible, which is nice, because Bradford pear isn't," Cantell said. "And they don't have any particularly terrible smell."

Windsor also plants the serviceberry, though Giroux notes it's not as hardy as the Bradford pear.

When asked if his department would consider eliminating its use of the potentially invasive tree, the city forester said they are watching the situation closely.

"If [invasion] becomes an issue here, we definitely can look at that, and maybe we shouldn't be planting along the right-of-way," he said.

"But at this point in time, we don't feel like planting [Bradford pears] in the middle of the city — kilometres away from our natural areas — [is an issue.] But it's definitely something that we'll be monitoring."