CLEMSON, SC – In the distance, next to a brick house in a neat subdivision, the trees rose over a wooden fence, showing everything that had made the Bradford pear so attractive: They were towering and robust and had in the early spring white flowers that turned their limbs into perfect cotton clouds.
But when David Coyle, a forest health professor at Clemson University, pulled into his pickup truck, he could see the monster those trees had spawned: an ominous jungle that had consumed a nearby clearing, where the same white flowers ran unchecked. bloomed in a thicket of tangled branches studded with thorns.
“If this tree grows somewhere, it won’t take long to take over the whole thing,” said Professor Coyle, an expert on invasive species. “It just wipes out everything underneath.”
From the 1960s, when suburbs sprouted over the south, clearing land for mazes of dead ends and garages for two cars, Bradford pears were the trees of choice. They were readily available, thrive in almost any soil, and were attractive in shape with mahogany-red leaves that lingered well into fall and flowers that appeared early in the spring.
The trees’ popularity rose during a period of transformation, as millions of Americans moved in search of the comfort and order that the suburbs had to offer. , “but the Bradford ornamental pear is unusually close to the ideal.”
But for all that promise, the trees posed an unmanageable threat, one that has plagued botanists, homeowners, farmers, conservationists, utilities and government officials in a growing swath of land on the East Coast and as far as Texas and the Midwest.
In South Carolina, the struggle has intensified. The state is in the process of blocking the sale and trade of the trees, becoming the second to do so. Professor Coyle, who tracks down plants and insects that have invaded South Carolina and tries to limit their damage, has organized “bounty” programs, in which people who provide evidence of a killed tree receive a native replacement in return.
The drawbacks of the Bradford pear were subtle at first. The white flowers, beautiful as they were, gave off a foul-smelling odor that almost smelled of fish. But as the trees got older, more and more negatives emerged. They had a poor structure of branches, making them prone to breaking and falling over in storms, sending limbs on power lines, sidewalks and the roofs of houses to beautify.
But the most far-reaching effect came when pear trees began to colonize open fields, farmland, riverbanks, and ditches, and began to colonize among the pines along Georgia’s highways up through the Carolinas, wiping out native species and turning ecosystems upside down. . The trees grow quickly, climbing up to 15 feet within ten years. (They can eventually grow 50 feet high and 30 feet wide.)
“You can’t miss it,” says Tim Rogers, the general manager of a company that sells plants and supplies to landscaping companies. “It is everywhere.”
The Bradford pear is a cultivar of the callery pear, meaning it is a variety produced through selective breeding – in this case coming up with a tree that didn’t have the thorns of some other varieties and wasn’t bothered by vermin.
But like the well-known plot of science fiction stories, the creation that seemed too good to be true was indeed too good to be true. The Bradford pear was billed as sterile, but that wasn’t quite right. Two Bradford pears can’t reproduce, scientists said, but they can cross-pollinate with other pear trees and their seeds are widely dispersed by birds.
It’s the resulting growth of the callery pears that alarms scientists: These trees are fast-spreading, have thorns three or four inches tall and close together, disrupting life for insects and other plants. “It’s a food desert for a bird,” Professor Coyle said, pointing out that the trees don’t support caterpillars and other herbivorous insects. “There is nothing to eat there.”
The callery pear, which is native to eastern Asia, was originally brought to the United States by federal researchers seeking a species resistant to fire blight that could be grown with the European pear to aid fruit production. But scientists recognized its potential as an ornamental tree and spurred the development of the Bradford pear.
The tree’s popularity was largely concentrated in the Southeast and along the Mid-Atlantic Coast. But it has been planted all over the country, on lawns and at the entrances of subdivisions and shopping centers.
“There are places where I’ve seen entire campuses planted with this one tree,” said Nina Bassuk, a professor and director of the Urban Horticulture Institute at Cornell University. “If you’re there in April, it’s just this sea of white.” But then, she added, “Bradfords became a problem.” Aging trees were falling apart, she said, and “we started noticing them in places where they hadn’t been planted.”
Officials in South Carolina have added the Bradford pear to the state’s list of pests this year and have instituted a ban that will take effect October 1, 2024. Ohio is the only other state to have taken similar measures, with a ban beginning in 2023. .
In other states, attempts to ban the trees have met resistance from the plant industry, researchers said, given the extent to which nurseries rely on their hardiness when using them as rootstock.
But in South Carolina, industry leaders said researchers convinced them alternatives were available. The decision was also easier as Bradford pears had plummeted in popularity as a landscape tree. “That factory has been in decline for a long time,” said Mr. Rogers, who is also the president-elect of an industry association SC Green.
In the past, customers sought out the trees, while their problems became more and more understood. “I would call them a necessary evil in terms of inventory,” said Mr. Rogers. But those days are long gone. “It’s not even in our catalog,” he added.
Scientists and officials said the public is developing a more sophisticated understanding of the consequences landscape choices can have. They point to the southwest, where drought-friendly designs have grown in popularity as water has become scarcer.
In the south, many were already aware of the threat of invasive species as the region has dealt with plants such as privet and especially kudzu, the Asian vine described as the plant that eats the south and covers much of the landscape. and grows. myths about the speed and range of its growth.
Still, state officials and homeowners have struggled with the countless Bradford pears planted in recent years. Last month on a Saturday, Professor Coyle traveled to Columbia, the state capital, for the last bounty exchange he hosted in South Carolina.
A flatbed trailer was loaded with dozens of native potted trees: Shumard oak, yellow poplar, persimmon, oriental red cedar, laurel magnolia. Professor Coyle noted that the trailer was parked in the shade of a Chinese pistachio, another non-native plant.
The dozens of people who signed up were able to pick up one of the native trees in exchange for proof of a conquered pear tree. (Posing a selfie with the tree sufficed.)
Valerie Krupp had printed out photos of the Bradford pears that had fallen over in her yard, smashed her gutters and cut off the corner of her house. “I wish I had removed them much sooner,” she said. She chose a live oak, a Shumard oak, and a magnolia, and she said she looked forward to seeing them grow and fill the void left by the pear trees. “I enjoyed the shade,” she said.
As Rick Dorn loaded his replacements into the back of his truck, he described the agony of dealing with a callery pear infestation. The thorns are perhaps the worst. “They will punch a hole in a tire,” he said.
His family owns an approximately 60-acre parcel near Irmo, a suburb of Columbia. The land has been overtaken by the trees, which, he noted, emerged around the same time as the subdivisions that now surround the property.
Professor Coyle believed his efforts have made some progress: hundreds of trees have been swapped through the bounty programs and he saw the ban as a big step. Yet they were incremental advances against a force of nature.
“I know this won’t be a quick fix,” Professor Coyle said. “If we’re honest, I’ll be working on callery peer my entire career.”
But incremental progress was better than none at all.
“Little by little, man,” he said. “Little by little.”