CLEVELAND — Referred to as the Bradford Pear or the Cleveland Select, the Callery Pear tree is known for its ornamental appearance, white blooms and, notoriously, pungent smell. An invasive tree, it has been banned from being planted or sold in Ohio starting January 2023.
Thirty-eight plants have been declared invasive in Ohio by the Ohio Department of Agriculture, and among them is the Callery Pear tree, which tends to aggressively spread and crowd out native plants.
If there was a plant version of "Jekyll and Hyde," it would be the Callery Pear tree, said Joe Boggs, assistant professor at Ohio University Extension Hamilton County, near Cincinnati.
"One thing started becoming evident they were still Jekyll trees. We love them They're tough trees," Boggs said. "We plant them where other trees have a problem. Then along the way, they started noticing that Bradfords tended to break apart, so people started working with breeding different types. Then we started noticing something that wasn't so good. We started noticing that little fruits were appearing on these streets."
Let’s start from the beginning
The presence of the Callery Pear tree began with unintended consequences. Native to Asia, the species is named after French missionary Joseph Callery, who first collected the tree in 1858. And unlike many of its family members, the Callery Pear put up a good fight against bacterial fireblight, a disease that threatens the common fruiting pear tree.
The original Callery pears were brought to the states to infuse its genes into fruiting pears as a solution to fight fireblight, a still very real problem affecting pear fruit trees. The crossbreeding of these plants didn’t produce the outcome researchers expected, and they serendipitously discovered that some crosses showed characteristics that could be of interest to the nursery and landscape industry.
The first plant produced out of this breeding project was the Bradford pear tree, and it was an immediate success. Its snowy white flowers, green leaves, glossy red color in the fall, and its inability to produce fruit, made it a hot commodity.
As they matured, the Bradfords began to reveal their Hyde persona. Arborists noticed the crotch angles of the trees were weak, and whenever there was a storm, cleanup of branches was inevitable. It was so common that some started referring to high wind storms as “pear storms,” Boggs said.
The real Mr. Hyde entered nature's chatroom when the Bradfords started producing fruit. They were generally regarded as occasional occurrences, but that soon changed.
Teresa Culley, professor of biological sciences at the University of Cincinnati, is credited with making the connection between the fruits and their sinister warning of what was to come in her groundbreaking paper, "The Beginning of a New Invasive Plant: A History of the Ornamental Callery Pear in the United States.”
“We [researchers and arborists] were speculating up until that point. We were thinking something is not right here, but also 30 years ago, I recommended Callery pears. We all did. They were such tough trees. They were the Jekyll trees, all good things about them.”
Culley established, through her research, that other cultivars (a plant variety that has been produced in cultivation by selective breeding) originating from slightly different plants, and then cloned, were crossing. Birds were eating the fruits of the Bradfords and then discarding their waste far away from the parent trees.
"For example, Bradfords could go on a date with Cleveland Select and produce viable offspring. So then we started seeing these pear trees showing up in places they didn't belong," Boggs said.
Boggs said Callery pears began to populate everywhere—along the roadway, abandoned fields and natural areas including wetlands.
A lesson learned
Hindsight is 20-20, and Boggs said he along with other arborists and the Department of Agriculture encouraged the planting of these trees, once sought after for their ornamental beauty.
"Unfortunately, we knew about this long before Callery pears, this idea of unintended consequences," Boggs said referring to plants like the bush honeysuckle and the poison hemlock, considered now the deadliest plant in Ohio, which were introduced back in the 1880s as ornamental plants.
"Callery pears, though, that really came as a real surprise. I mean this idea of self-incompatibility seemed pretty strong. But like I said, that wasn't a tree that was directly introduced and then went wild. That was a tree that by the time it was introduced, had already gone through some work, had already gone through some selection to where we thought it was going to be OK," Boggs said.
What to do if you have a Callery Pear tree
Don’t panic. Property owners don’t have to remove existing trees in their yards because the ban only applies to new trees from being sold or plants.
“If you have the ability to take trees down in a location, go ahead. But if they're in your yard, if you have one in your yard, don't feel bad," Boggs said. "Don't be made to feel bad. Telling people to take these out of their yard is like saying, Well, don't blow that dandelion fluff. If you blow dandelion fluff, you're going to spread dandelions everywhere. Well, it's already too late."
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