Carole Bergmann pulls her small parks department SUV into an aging 1980s subdivision in Germantown, Maryland, and takes me to the edge of an expansive meadow. A dense screen of charcoal-gray trees stands between the open ground and the backyards of several houses.
The trees are callery pears, the escaped offspring of landscape specimens and street trees from the neighborhood. With no gardener to guide them, the spindly wildlings form an impenetrable thicket of dark twigs with 3-inch thorns.
Bergmann, a field botanist for the Montgomery County Parks Department, extricates herself from the thicket and in the meadow shows me that what I take to be blades of grass are actually shoots of trees, mowed to a few inches high. There are countless thousands, hiding in plain sight in Great Seneca Stream Valley Park. If it were not cut back once a year, the meadow would become like the adjacent screen, wall upon wall, acre upon acre of black-limbed, armored trees worthy of Sleeping Beauty’s castle.
“You can’t mow this once and walk away,” said Bergmann, who began her 25-year career in the department as a forest ecologist but has been consumed by an ever-pressing need to address the escape of the Bradford pear and other variants of callery pear, a species that originated in China, along with other invasive exotics.
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The U.S. Agriculture Department scientists who gave us the Bradford pear thought they were improving our world. Instead, they left an environmental time bomb that has now exploded.
From the 1960s to the 1990s, the callery pear was the urban planner’s gift from above. A seedling selection named Bradford was cloned by the gazillion to become the ubiquitous street tree of America’s postwar suburban expansion.
Best of intentions
The Bradford pear seemed to leap from an architect’s idealized rendering. But in this case, reality outshone the artist’s vision. It was upright and symmetric in silhouette. It exploded with white flowers when we most needed it, in early spring. Its glossy green leaves shimmered coolly in the summer heat, and in the fall, its foliage turned crimson, maroon and orange – a perfect New England study in autumnal color almost everywhere it grew.
And it grew everywhere. It flourished in poor soil, wet or dry, acidic or alkaline. It shrugged off pests and diseases, it didn’t drop messy fruit like mulberries or crab apples. Millions of Bradford pears would be planted from California to Massachusetts and would come to signal the dream and aspirations of postwar suburbia. Like the cookie-cutter suburbs themselves, the Bradford pear would embody that quintessentially American idea of the goodness of mass-produced uniformity.
But like a comic book supervillain who had started off good, the Bradford pear crossed over to something darker. It turned from thornless to spiky, limber to brittle, chaste to promiscuous, tame to feral. Most of all, it became invasive. It is now an ecological marauder destined to continue its spread for decades, long after those suburban tract houses have faded away. Generations yet to be born will come to know this tree and learn to hate it.
It is at its most conspicuous in early spring, when it bursts into flower. Suddenly whole rural landscapes – meadows, old pastures, woodland edges, ditches, the sides of highways and railroads – are lit up by its blossoms. From early March to mid-April, you can now track the arrival and progression of spring in the United States not as amber waves of grain but as a frothing tide of Bradford pear.
You might even enjoy its beauty, until you realize that it is squeezing out native flora and reducing biodiversity. As eye-catching as the flowers are, they are simply the start of the seasonal march of this invader. Six months after the blooms appear, clusters of seedy berries invite birds to fatten up for winter. In the bird’s droppings, the seeds will germinate and advance, becoming ever more genetically diverse in the process and making the pear ever more adapted to its own spread.
Its invasive tendencies became widely noticed by the late 1990s, and by the mid-2000s, it had become a weed in the District and 19 states, from Texas to New York. “While callery pear was introduced with the best of intentions, it now seems that a plague is truly upon us,” botanist Michael Vincent wrote at the time. It has now spread to 29 states.
To China in search of seeds
The roots of the Bradford pear fiasco go back more than a century, and had nothing to do with decorating suburbia. By the turn of the 20th century, Northern California and southern Oregon had become the centers of pear production in the United States. The common or European pear was a high-value fruit; in one Oregon county alone, Jackson, the pear industry in 1916 was worth a mind-boggling $10 million.
But the orchards were threatened by a new disease called fire blight. George Roeding, a nurseryman in Fresno, wrote in 1916 that “in the San Joaquin Valley, which sixteen years ago was one of the great pear producing sections of California, the pear has been absolutely wiped out of existence.”
In Talent, Oregon, a plant scientist named Frank Reimer was using a test orchard to work on fire-blight control and found that the callery pear, first brought to the States in 1908, was highly resistant to fire blight and might be used as a rootstock onto which varieties of the European pear could be grafted. The much smaller callery fruit is used to make tea in China but is considered inedible.
But to take his research further, Reimer needed lots of genetically rich wild seed from China. He turned to David Fairchild, a dynamic young botanist in Washington. Fairchild is best remembered as the guy who helped bring the Japanese cherry blossoms to the capital, by first growing 125 imported trees on his estate in Chevy Chase, Md.
Fairchild headed the Agriculture Department’s Office of Foreign Seed and Plant Introduction. He traveled far during his career in search of new plants, but he relied on another explorer, Frank Meyer, in the quest for a super-pear. Meyer, an emigre from the Netherlands, had already explored extensively in northern and central China when Fairchild tapped him, in 1916, to go to southern China. (Meyer is best known for giving Americans the lemon variety named after him.)
In an age before passenger jets and digital communication, the quest for the callery pear would be no quick or easy excursion. A century ago, plant explorers needed an extraordinary set of skills to complete their missions and survive a range of perils.
A haunting image of Meyer in China is captured in a 1908 photo. With a big black beard, sheepskin leggings and a staff, he is seen gazing into the distance from a mountainous, arid landscape. All about him, burlapped cuttings rest like tablets brought down from Mount Sinai. He is in his early 30s but seems older.
Meyer left Washington in mid-August of 1916, traveling west to see Reimer’s pear trials in Oregon and finally departing Seattle bound for Japan on the last day of summer. Within a couple of months, he had sent six large shipments of seed from Beijing containing pine nuts, walnuts and chestnuts, but no callery pear. Fairchild, exasperated that Meyer was hanging around Beijing, urged him to make his way up the Yangtze River to look for the callery. “You must not leave any stone unturned to secure it,” he wrote. The correspondence between Meyer and Fairchild form part of an archive of the Chinese expedition in the National Agricultural Library in Beltsville, Md.
Meyer eventually made his way to Yichang, a four-day boat ride from Hankou (now Wuhan) up the Yangtze, and he soon found wild-growing callery pears, if not in the extravagant amounts Reimer was seeking.
By late summer, he had made his way to the area around Jingmen, today a large city in Hubei province.
He sent his first shipment of callery pear seed to Fairchild in September, and the following month he teamed up with Reimer and gathered another 25 pounds of seed – enough to grow a small forest of callery pears.
The seed that Meyer and others would collect ended up in Reimer’s test orchard in Oregon and the U.S. Plant Introduction Station in Glenn Dale, then a rural enclave in Maryland’s Prince George’s County.
In the early 1950s, a horticulturist at Glenn Dale named John Creech began to see the callery pears there not as a rootstock for the common pear but as an extraordinarily handsome and tough street tree in its own right. He latched on to a single specimen that had been grown from seed that was not part of Meyer’s shipment but acquired soon afterward in Nanjing as part of Fairchild’s search.
The tree was 30 years old when Creech first evaluated it, and judging from his later writings, he was besotted by this specimen. He was struck by its vigor, its handsome, mature spread and its evident ornamental qualities. But a plant’s value lies too in what it is not. This one tree did not have the thorns of other callery pears; it was free of diseases and pests and held together in storms. In selecting this individual to mass-produce, Creech named it Bradford after the station’s former head, F.C. Bradford. This specimen’s resilience in storms belied what would become a major problem with its mass-produced Bradford clones: Tight branch-to-trunk angles and congested branching invited the limbs to break apart.
Before releasing the Bradford ornamental pear to the nursery trade, Creech decided to trial it in the Washington suburb of University Park, which was then treeless and had difficult soil – perfect for putting this wondertree to the test. He planted 180 saplings in 1954.
In the University Park planting, there was something that should have raised alarms. On a few grafted trees where the scion had failed, the rootstock had produced suckers that then bloomed. These flowers, with the help of bees, caused the “sterile” street trees to set viable fruit.
Soon, commercial plant breeders were bringing to market other varieties of the callery pear, and by the mid-1980s, a dozen or so were available for planting.
It seems that the callery pear has been a curse to those who tried to master it. We brought it to an alien environment, selected one for unnatural propagation and then fused genetically different individuals together. We planted it across the entire continental United States, seeding its eventual spread. Today it is a roving, free-range freak.