Bradford Pear Trees Blamed for Foul Odor Around Philadelphia

The invasive species is known for its unpleasant smell, which could linger for up to two weeks.

Apr. 3, 2026 at 5:06pm

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A highly structured abstract painting in soft earth tones, featuring sweeping geometric arcs, concentric circular patterns, and precise botanical spirals, conceptually representing the complex biological forces behind the invasive nature of the Bradford Pear tree.An abstract visualization of the invasive growth and hybridization capabilities that make the Bradford Pear tree a persistent nuisance in Philadelphia's urban landscape.Callery Today

Philly residents have been noticing a new unpleasant smell in the city, which experts say is likely coming from the Bradford Pear trees. These invasive trees, originally imported from China, are known for their strong, rotting-fish-like odor during blooming season. While the trees have attractive white flowers, they also present issues like weak branches and the ability to hybridize with other pear trees, making them a problematic species that the state has tried to curb.

Why it matters

The Bradford Pear trees are an invasive species that can crowd out native plants, and their weak branches make them prone to damage in storms. The foul odor they produce during blooming season is an annual nuisance for Philadelphia residents, highlighting the broader challenges of managing problematic non-native plant species in urban environments.

The details

Bradford Pears, a specific type of Callery pear tree, were originally imported from China in the 1900s to combat a bacterium affecting other pear trees. However, the trees quickly became problematic, as their strong smell is often likened to rotting fish, and their ability to hybridize with other pear trees allows them to spread invasively. Additionally, the trees' weak branches make them susceptible to breaking in heavy storms. Despite efforts by the Pennsylvania Department of Agriculture to curb the sale and distribution of Callery pear trees, they remain a common sight around Philadelphia, lining streets and filling the air with their unpleasant odor during blooming season.

  • The Bradford Pear trees typically bloom for about one to two weeks in the spring.
  • The Pennsylvania Department of Agriculture added the Callery pear tree to the state's noxious weed list in 2021.
  • In 2024, stop or destruction orders were issued to merchants selling or distributing the Callery pear in Pennsylvania.

The players

Pamela Morris Olshefski

The plant collections manager at Morris Arboretum & Gardens, who provided expert commentary on the Bradford Pear trees.

Pennsylvania Department of Agriculture

The state agency that added the Callery pear tree to the noxious weed list and issued orders to curb its sale and distribution.

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What they’re saying

“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.”

— Pamela Morris Olshefski, Plant Collections Manager, Morris Arboretum & Gardens

“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.”

— Pamela Morris Olshefski, Plant Collections Manager, Morris Arboretum & Gardens

What’s next

The Pennsylvania Department of Agriculture will continue to enforce the noxious weed designation and destruction orders for Callery pear trees in an effort to curb the spread of this invasive species.

The takeaway

The Bradford Pear tree's unpleasant odor is an annual nuisance for Philadelphia residents, but it also highlights the broader challenges of managing problematic non-native plant species in urban environments. Despite efforts to limit their spread, these invasive trees remain a common sight in the city, underscoring the need for continued vigilance and action to protect native ecosystems.