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Philly is, by nature, a city full of smells (and oftentimes, unpleasant ones). But you may have noticed a new smell in the mix this week.
It could be Bradford Pear trees in the city, said Pamela Morris Olshefski, the plant collections manager at Morris Arboretum & Gardens.
“The smell is really that the tree is trying to attract flies to help pollinate the plant, and flies and beetles that like stinky things,” she said.
Bradford Pears are a specific type of Callery pear tree.
The flowering white trees were imported from China in the 1900s to combat a bacterium affecting other pear trees.
They quickly became popular for their fast growth, disease resistance and abundant flowers.
“It has nice, pretty blooms in the spring, and it’s a lovely visual tree,” Olshefski said.
But the trees quickly presented issues. Their smell is often likened to that of rotting fish, and controlling their growth is difficult.
“It turned out that these pears could hybridize with other pear trees and then actually produce non-sterile fruit, which would mean that they start to spread and can become invasive,” she said.
Birds and other animals can spread the seeds, and the invasive growth of the species can “crowd out” native species.
Another problem is their weak branches.
“They’re also a little bit on the weaker side of wood, so the trunk grows, and then right from the main trunk is where all the branches come out of it,” she said. “And when that happens, they are very susceptible to breaking when there’s a really heavy snowstorm or a lot of wind.”
The flowering white trees are planted all over the city – down side streets and around Center City.
The Callery pear tree was added to the Pennsylvania noxious weed list by the PA Department of Agriculture in 2021. And stop or destruction orders were issued to merchants selling or distributing the Callery pear in 2024.
Olshefski said people living around these trees should do what they can.
“You should do ‘pre-care’ if you have one on your street or by your house if you can’t necessarily just remove it. You can also help to minimize the weight of the canopy of the tree.”
Despite this, it’s hard to tell if Callery pears will ever be eradicated or how quickly they will continue to be removed.
As for how long you’ll have this smell, Olshefski said it depends.
“They’ll bloom for about one to two weeks, depending on if there’s sort of a microclimate in the city,” she said.
She said some trees aren’t in full bloom yet, but that the smell will likely last for two weeks post-bloom.