CLEMSON, South Carolina – In the distance, near a brick house in a neat neighborhood, trees towered over a wooden fence, showing everything that made the Bradford pear so attractive: they were tall and sturdy, and in early spring had white flowers that turned their limbs into perfect cotton clouds …
But when David Coyle, professor of forest health at Clemson University, pulled up in his pickup truck, he saw the monster spawned by these trees: an impenetrable jungle that swallowed an open area nearby, where the same white flowers bloomed uncontrollably in a thicket of tangled branches strewn with thorns.
“When this tree grows somewhere, it doesn’t take long for it to take over,” said Professor Coyle, an expert on invasive species. “It just erases everything underneath.”
Since the 1960s, when suburbs have sprung up in the south, clearing land for labyrinths of dead ends and two-car garages, Bradford pears have been the trees of choice. They were readily available, could grow in almost any soil, and were attractively shaped with mahogany leaves that persisted in deep fall and flowers that emerged in early spring.
The popularity of trees skyrocketed during the transformation era, as millions of Americans moved in search of the comfort and order that suburban areas were supposed to provide. “Few trees have all the qualities you want,” declared the gardening pages of The New York Times in 1964. “But the Bradford ornamental pear is unusually close to ideal.”
Yet for all these promises, trees posed a bulky threat that annoyed botanists, homeowners, farmers, conservationists, utilities and government officials across much of the country across the East Coast and into Texas and the Midwest.
In South Carolina, the fight intensified. The state is in the process of banning the sale and trade of trees, becoming the second state to do so. Professor Coyle, who has been tracking plants and insects invading South Carolina and trying to limit their damage, has set up bounty programs in which people who bring evidence of a dead tree are given local replacements in return.
At first, the shortcomings of the Bradford pear were barely noticeable. Its white flowers, beautiful as they were, exuded a fetid odor, almost fishy. But as the trees got older, more and more negatives appeared. They had poor branch structure, which left them prone to tearing and toppling over during a storm, throwing limbs on power lines, sidewalks, and rooftops that they had to decorate.
But the most far-reaching consequences came when pears began to colonize open fields, farmland, riverbanks and ditches and climbed between pine trees along the highway leading from Georgia up through the Carolina, displacing native species and destroying ecosystems. The trees grow rapidly, reaching 15 feet in a decade. (They can eventually grow to 50 feet high and 30 feet wide.)
“You can’t miss this,” said Tim Rogers, CEO of a company that sells plants and supplies to landscape companies. “It’s everywhere.”
The Bradford pear is a cultivar of kalleri pear, which means it is a selective breeding variety – in this case, by creating a tree that lacks the thorns of some other varieties and does not bother pests.
But like the familiar plot of science fiction stories, a creature that seemed too good to be true was actually too good to be true. Pear Bradford was declared sterile, but this was not entirely true. Scientists said the two Bradford pears cannot reproduce, but they can cross-pollinate with other pear trees, and their seeds are widely distributed by birds.
This is the induced growth of the calleria pear that worries scientists: these trees grow rapidly, have thorns three or four inches long, and cluster close together, disrupting the life of insects and other plants. “This is food for birds,” said Professor Coyle, noting that trees do not feed caterpillars and other herbivorous insects. “There’s nothing to eat there.”
The kalereya pear, native to East Asia, was originally brought to the United States by federal researchers looking for a disease-resistant species that could interbreed with the European pear to increase fruit production. But scientists realized its potential as an ornamental tree, which spurred the development of the Bradford pear.
The tree’s popularity was mainly concentrated in the southeast and along the Mid Atlantic coastline. But it is planted all over the country, dotting lawns and entrances to subdivisions and shopping centers.
“There are places where I have seen entire campuses planted with this tree,” said Nina Basuk, professor and director of the Urban Horticultural Institute at Cornell University. “If you’re there in April, it’s just a sea of white.” But then, she added, “Bradfords became a problem.” According to her, the aging trees were falling apart, and “we began to notice them where they were not planted.”
This year, officials in South Carolina added the Bradford pear to the state’s plant pest list and initiated a ban that will take effect October 1, 2024. Ohio is the only state to have adopted similar measures, with a ban starting in 2023. …
In other states, efforts to ban trees have met with resistance from crop production in other states, the researchers said, given how much nurseries rely on their endurance to use them as rootstock.
But in South Carolina, industry leaders said researchers had convinced them that there were alternatives. The solution was easier because the popularity of Bradford pears as garden trees plummeted. “This plant has been in decline for a very long time,” said Mr. Rogers, who is also president-elect of the SC Green industry association.
In the past, customers have looked for trees even when their concerns became clearer. “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 that the public is increasingly aware of the consequences of the choice of landscape design. They point to the Southwest, where drought protection construction has become popular as water becomes scarcer.
In the south, many were already familiar with the threat of invasive species as the region struggled with plants such as privet and most notably kudzu, an Asian vine, described as a plant that devoured the south, covering much of the landscape and multiplying. myths about the rate and scale of its growth.
However, government officials and homeowners are left to grapple with the countless numbers of Bradford pears planted in years past. Professor Coyle traveled to Columbia, the state capital, one Saturday last month for the last of his sponsored bounty exchanges across South Carolina.
The flatbed trailer was loaded with many local trees in pots: Shumard oak, yellow poplar, persimmon, oriental red cedar, sweet laurel magnolia. Professor Coyle noticed that the trailer was parked in the shade of Chinese pistachio, another non-native plant.
Dozens of signers could harvest one of the native trees in exchange for proof of a defeated pear tree. (A selfie with a tree was enough.)
Valerie Krupp printed out photographs of Bradford pears that overturned in her yard, ruined the gutters and stabbed the corner of the house. “I would like to get rid of them much sooner,” she said. She chose live oak, Shumard oak and magnolia and said she looked forward to their growth and filling the void left by the pear trees. “I liked the shade,” she said.
Loading spare parts into the back of his truck, Rick Dorn described the anguish associated with a callery pear infection. The thorns can be the worst part. “They’re going to punch a hole in the tire,” he said.
His family owns a plot of about 60 acres near Irmo, a suburb of Colombia. The land was covered in trees, which, he noted, emerged around the same time as the areas that now surround the area.
Professor Coyle believed that his efforts had made some progress: hundreds of trees were replaced as part of the reward programs, and he saw the ban as an important step. However, they were a gradual advance against the forces of nature.
“I know this will not be a quick fix,” said Professor Coyle. “To be honest, I will be working on the calleric pear my entire career.”
But gradual progress is better than no progress.
“Little by little, buddy,” he said. “Little by little.”