Remarkable for their resilience and beauty, Callery pear trees and their cultivars have become an invasive nightmare.
Published January 25, 2023 12:29PM EST
Here in New York City, Callery pear trees line the streets boasting showy clouds of white blooms each spring. Reaching to the sky, sometimes they’re so fluffy they create block-long floral tunnels. With their storybook tree shape and profusion of petals and leaves, they provide greenery and cooling shade and play host to local and visiting birds. Despite their “unique” springtime aroma (variously described as smelling like, uhm, fish, vomit, or bleach) the Callery pear is a fan favorite of many.
Adding to their popularity is their resilience. Callery pears (Pyrus calleryana) and their cultivars—like the ubiquitous Bradford pear—are especially hardy. While this trait makes them valuable as street trees and desirable to gardeners, it also makes them a terror in the wild. Forming dense thickets that crowd out other plants, they threaten native wild plants that can’t compete for soil, water, and space. And they’ve started taking over.
Now, Ohio has become the first state to ban the sale of Callery pear trees. A similar ban will go into effect in South Carolina starting in 2024, as reported by the University of Cincinnati.
“We’re proud to be the first to deal with this invasive plant,” Jennifer Windus, president of the Ohio Invasive Plants Council, told University of Cincinnati. Windus added, “South Carolina is next. I think we started something.”
The Callery pear was first brought to the United States In the early 20th century as a remarkably resilient candidate to replace the edible French pear (Common pear), which was being wiped out by fire blight in the Pacific Northwest.
In “The Rise and Fall of the Ornamental Callery Pear Tree,” Theresa Culley, the head of the University of Cincinnati’s Department of Biological Sciences, described the creation of the Callery cultivar, the Bradford pear, and its subsequent rise to fame. In 1954, two Bradford clones were planted in a residential subdivision in University Park, Maryland, for a street tree study. The Bradford “swiftly became quite popular for its rapid growth, attractive foliage that was retained into late fall, extremely showy and abundant flowers in early spring, and its overall hardiness,” wrote Culley. “The cultivar was commercially released around 1961 and then planted widely across the eastern United States in residential areas.”
Culley tells Treehugger that the Ohio ban includes all cultivars along with the species itself.
“Seedlings of pear trees are now also showing up in the forest understory. They are very difficult to remove because they have a very long taproot,” says Culley, who also serves on the Ohio Invasive Plants Council and is a member of the Ohio Invasive Plant Advisory Committee, which advises the Ohio Department of Agriculture on regulation.
“They’re extremely hardy. They can grow pretty much anywhere. They have abundant flowers that attract all kinds of pollinators so they end up with abundant fruit that birds disperse,” she adds.
As an illustration of just how tenacious these trees are, consider 9/11’s “Survivor Tree.” This New York City Callery pear spent a month under rubble at Ground Zero. Found nearly lifeless with nary but a few leaves, it managed to rebound back to health and now thrives in the green space at the National 9/11 Memorial & Museum.
And New York City is not the only urban area that has gone big with the pear trees. Cully tells Treehugger there are many Callery pear street trees in Ohio (and other states). When asked if Ohio would be replacing them, Culley says, “Some of these are on municipal-controlled properties, commercial properties (think in parking islands in parking lots), or on private property. As you may imagine, it would be a huge cost to replace all of these trees.”
That said, she continues, “These commercial trees usually only have a lifespan of 15-20 years before they are blown over or split under ice or wind conditions. So likely what will happen is that these Callery pear trees will be slowly replaced as they die—ideally by non-invasive trees or native species.”
She adds that some homeowners are already replacing their Callery pear trees with other non-invasive species. “I think we will start to see more of that over the next few years.”
“Customer demand disappeared when it was realized that this plant was an invasive issue. Our nursery stopped producing these trees. I think most nurseries did the same,” echoed William Kyle Natorp, president and CEO of the Cincinnati nursery Natorp’s.
For those of us who feel attached to our tough and beautiful Callery street and garden trees, now would be a good time to move on to new tree crushes. (Even the National Park Service is on board, advising the public in no uncertain terms: “Do not plant Callery pear or any cultivars including the well-known Bradford pear.”)
Natorp said there is a wide selection of alternatives for all types of conditions. “Ideally, a mix of trees is the best choice when planting multiple plants,” he added. “This diversity helps protect against a future unknown disease or pest like the emerald ash borer,” Natorp said.
Culley tells Treehugger there are some great recommendations for what to plant instead, depending on locations and the traits desired, like the white spring blooms, the shape of the tree, its tolerance, et cetera.
“For example, Alleghany Serviceberry, and Green Hawthorn are good. I personally have a Yellowwood in my front yard—it is really beautiful and has white flowers,” she says, “… that actually smell really good.”