CLEMSON, SC – In the distance, next to a brick house in a tidy subdivision, trees towered above a wooden fence, showing everything that had made the Bradford Pear so alluring: They were imposing and sturdy and, in early spring, had white flowers that turned their limbs into perfect clouds of cotton.
But when David Coyle, professor of forest health at Clemson University, pulled up in his van, he could see the monster these trees had spawned: a menacing jungle that had consumed nearby open land, where the same white flowers bloomed uncontrollably in a thicket of tangled branches strewn with thorns.
“When that tree grows somewhere, it doesn’t take long to take hold of the whole thing,” said invasive species expert Professor Coyle. “It erases everything below. “
From the 1960s, as suburbs pushed south, clearing land for cul-de-sac mazes and two-car garages, Bradford pears were the trees of choice. They were readily available, could thrive in almost any soil, and had an attractive shape with mahogany red leaves that lingered deep into fall and flowers that appeared in early spring.
The popularity of trees skyrocketed during a time of transformation, as millions of Americans moved in search of the comfort and tidiness that suburban neighborhoods were designed to offer. “Few trees have all of the desired attributes,” the New York Times gardening pages said in 1964, “but the Bradford ornamental pear comes exceptionally close to the ideal.”
Yet despite all these promises, trees have posed a heavy threat, a threat that has upset botanists, landowners, farmers, conservationists, utility companies and government officials in growing parts of the country across. the east coast and reaching Texas and the Midwest.
In South Carolina, the fight escalated. The state is in the process of banning the sale and trade of trees. Professor Coyle, who tracks down plants and insects that have made their way into South Carolina and tries to limit their damage, has organized ‘bounty’ programs, where people who provide evidence of a downed tree get a replacement. native in return.
The downsides of the Bradford pear were subtle at first. Its white flowers, as pretty as they were, gave off a foul odor that almost smells of fish. But as the trees got older, more and more negatives appeared. They had poor branching structure, leaving them prone to breaking and tipping during storms, sending limbs over power lines, sidewalks, and roofs of houses they were supposed to spruce up.
But the most significant consequence came when pear trees began to colonize open fields, farmlands, river banks and ditches, and rise between pines along highways from Georgia to the Carolinas, eliminating native species and disrupting ecosystems. Trees grow quickly, reaching up to 15 feet in a decade. (They can eventually grow to 50 feet tall and 30 feet wide.)
“You can’t miss it,” said Tim Rogers, general manager of a company that sells plants and supplies to landscaping companies. “It’s everywhere.”
The Bradford pear is a cultivar of the callery pear, which means that it is a variety produced by selective breeding – in this case, by designing a tree that lacked the thorns of some other varieties and which was not bothered by pests.
But like the familiar plot of science fiction stories, the creation that seemed too good to be true was, indeed, too good to be true. The Bradford pear had been presented as sterile, but that was not entirely correct. According to scientists, two Bradford pears cannot reproduce, but they can interbreed with other pear trees and their seeds are widely spread by birds.
It is the resulting callused pear growth that alarms scientists: These trees spread rapidly, have thorns three or four inches long, and cluster together, disrupting the life of insects and other plants. . “It’s a food desert for a bird,” said Professor Coyle, noting that the trees do not feed caterpillars and other herbivorous insects. “There is nothing to eat there.”
The callused pear, native to East Asia, was originally brought to the United States by federal researchers who were looking for a species resistant to late blight that could be crossed with the European pear to enhance fruit production. But scientists recognized its potential as an ornamental tree, stimulating 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 across the country, dotting lawns and entrances to housing estates and shopping malls.
“There are places where I’ve seen entire campuses planted with this tree,” said Nina Bassuk, professor and director of the Urban Horticulture Institute at Cornell University. “If you’re there in April, it’s just that sea of white.” But then, she added, “Bradfords became a problem.” Aging trees were collapsing, she said, and “we started to notice them in places where they weren’t planted.”
Authorities in South Carolina have added the Bradford pear to their state list of plant pests this year, and launched a ban which will come into force on October 1, 2024. Ohio is the only other state to have took similar action with callused pear, with a ban from 2023. Delaware adopted more radical legislation this year which prohibits the sale, import or planting of any invasive species.
In other states, efforts to ban the trees have met resistance from the plant industry, the researchers said, as nurseries rely on their hardiness to use it as a rootstock.
But in South Carolina, industry leaders said researchers convinced them alternatives were available. The decision was also easier because, as a landscaping tree, Bradford pears had fallen in popularity. “This plant has been in decline for a very long time,” said Mr. Rogers, who is also the president-elect of SC Green, an industry association.
In the past, customers had researched trees, even as their problems became more widely understood. “I would call them a necessary evil in terms of inventory,” Rogers said. 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 that landscaping choices can have. They point to the southwest, where drought-friendly designs have become increasingly popular as water has become more scarce.
In the South, many were already aware of the threat of invasive species as the region grappled with plants like privet and, above all, kudzu, the Asian vine described as the plant that ate the south, covering much of the landscape and reproduction myths about the speed and scope of its growth.
Yet state officials and homeowners face the countless Bradford pears planted in recent years. On a Saturday last month, Professor Coyle traveled to Columbia, the state capital, for the last of the bounty swaps he held across South Carolina.
A flatbed trailer was loaded with dozens of native potted trees: Shumard oak, yellow poplar, persimmon, eastern red cedar, Sweet Bay magnolia. Professor Coyle noted that the trailer was parked in the shade of a Chinese pistachio, another non-native plant.
Dozens of people registered could recover one of the native trees in exchange for proof of a defeated pear tree. (A selfie posing with the tree was enough.)
Valerie Krupp had printed photographs of the Bradford pears that had spilled in her yard, ruining her gutters and cutting the corner of her house. “I would have liked to have taken them out much sooner,” she said. She chose a Living Oak, a Shumard Oak, and a Magnolia, and said she looked forward to them growing and filling the void left by the pear trees. “I enjoyed the shade,” she said.
As Rick Dorn loaded his replacements into the bed of his truck, he described the torment of dealing with a callery pear infestation. Thorns could be the worst. “They’re going to punch a hole in a tire,” he said.
His family owns an expanse of approximately 60 acres near Irmo, a suburb of Columbia. The land has been overgrown with trees which, he noted, appeared around the same time as the subdivisions that now surround the property.
Professor Coyle believed his efforts had made progress: hundreds of trees had been traded through bounty programs, and he viewed the ban as a major step forward. Yet these were gradual advances against a force of nature.
“I know it won’t be a quick fix,” Professor Coyle said. “If we’re honest, I’ll be working on Callery Pear my entire career. “
But incremental progress was better than nothing at all.
“Little by little, man,” he said. “Step by step.”