Beyond the Books: Callery Pear

by Steve Sass and Amanda Smith

Introduction and History of the Callery pear (Pyrus calleryana)

Like many 21st-century landscapes, the New Carlisle Olive Township Library contains several Callery pear (Pyrus calleryana) trees. Once heralded as tremendous urban and suburban street trees, Callery pears have spectacularly fallen from grace in the past couple of decades. So much, in fact, that in many places, they are now illegal to plant. In this edition of Beyond the Books, we’ll dive into the introduction and history of one of America’s most infamous tree species.

The introduction of Callery pear to the United States dates back 118 years. As America’s common (i.e., edible) pear trees (Pyrus communis) suffered from the bacterial disease fire blight (Erwinia amylovora), American plant explorers traveled to eastern Asia to search for disease-resistant pear species (Pyrus spp.) to breed with Pyrus communis. They encountered two promising species, and in 1908, explorer E.H. “Chinese” Wilson introduced the first seeds of Callery pear (Pyrus calleryana) to Harvard University’s Arnold Arboretum. Seven years later, the United States Department of Agriculture’s (USDA) Office of Seed and Plant Introduction dispatched Danish-born plant explorer Frank Meyer (born Frans Meijer) to China. Between 1916 and 1918, Meyer procured over 5,000 pounds of marble-sized Callery pear fruit, of which he cleaned and shipped 100 pounds of seed to Professor Frank C. Reimer at Oregon State College’s Southern Oregon Experiment Station.

At age 41, Frank Meyer was a veteran plant importer of the USDA’s Office of Seed and Plant Introduction. Having already completed three tours of duty in Asia, Meyer was a prolific plant collector, close associate, trusted employee, and an obvious choice of David Fairchild (the Office’s chair and husband of Alexander Graham Bell’s daughter Marian) to fulfill the mission.

Even for a seasoned traveler, collecting and cleaning 5000 pounds of fruit in a far-off land was physically and mentally exhausting, especially with the isolation brought about by Chinese civil unrest. In written correspondence with Fairchild, Meyer frequently wrote about his declining mental health and his desire to have the fourth Asian mission be his last. In a candid display of his mental state, Meyer sent a letter to Fairchild that contained the line, “It often seems we do not live ourselves any longer but that we are being lived.”

Sadly, Meyer’s letter to Fairchild would be his last. In June 1918, while traveling on a steamship to Shanghai, Meyer reportedly left his cabin at 11:20 p.m. and disappeared. A day later, a Chinese sailor found his body floating face down in the Yangtze River. There was no sign of foul play, and to this day, whether his death was a homicide, suicide, or accident is still debated among historians.

Following Meyer’s death, Reimer continued importing seed and planted thousands of trees at the Southern Oregon Experiment Station and at the U.S. Plant Introduction Station in Glenn Dale, Maryland. Unfortunately for the legacy of Reimer, Meyer, and Fairchild, plant breeders never successfully created a commercially viable Pyrus communis/P. calleryana hybrid. However, their efforts were not completely in vain, as plant breeders eventually began successfully grafting Pyrus communis onto hardy Pyrus calleryana rootstock. Ironically, the tree imported to solve an agricultural problem would later cause widespread ecological damage.

Although the trees sat largely forgotten for decades, 1952 was pivotal in the Callery pear’s story. While working at the USDA’s facility in Glenn Dale, Maryland, botanist John Creech noticed one standout among the 30-plus-year-old trees growing in seed lot #46261. Along with Callery pear’s spring flowers and leaves lasting late into the fall, Creech recognized that this particular tree’s shape and lack of thorns could make it a desirable ornamental landscape tree. As a result, he propagated the standout tree asexually through cuttings, thus ensuring each offspring tree would be genetically identical and retain the same desirable traits as its parent. He named his Callery pear variety ‘Bradford’ after Frederick Charles Bradford, his former boss at the USDA who had passed in 1950.

Two years later, Creech planted some of his cloned trees in the nearby Washington suburb of University Park, where they quickly gained popularity. In addition to their desirable aesthetic features, they were also incredibly hardy and apparently well suited as urban and suburban landscape trees. Even decades earlier, while in China, USDA plant explorer Frank Meyer noted Callery pear’s resilience and its ability to thrive in a wide range of habitats. Another benefit of the ‘Bradford’ cultivar planted as street trees was its relatively low fruit production compared to the trees growing at the Glenn Dale facility. This meant that as long as ‘Bradford’ stayed away from other Callery pear varieties, its fruit production would be minuscule.

Before long, the ‘Bradford’ cultivar proved vulnerable. Most notably, its form lends itself to weak branches, which frequently break off in storms. The American nursery industry responded by introducing new cultivars of Callery pear, including ‘Whitehouse,’ ‘Capitol,’ and ‘Aristocrat.” In 2005, the Society of Municipal Arborists even named the ‘Cleveland Select’ (aka ‘Chanticleer’) cultivar as the 2005 Urban Tree of the Year. Callery pears became so regionally popular that St. Joseph County even contains a subdivision named after them (Bradford Shores).

The cultivars quickly created ecological problems. Whereas isolated populations of ‘Bradford’ produced very little fruit, the cultivars began cross-breeding and producing copious amounts. Palatable to birds, Callery pear trees escaped cultivation and quickly began spreading across the eastern United States, where they frequently invade grasslands and old fields. Each spring, acres of white flowers from monocultures of escaped Callery pear populations are conspicuous along South Bend’s Nimtz Parkway.

Callery pear damages local ecosystems by spreading rapidly and forming dense stands where other plants cannot survive, thus reducing biodiversity. Realizing its potential to inflict substantial damage, six eastern states have passed laws banning the sale, purchase, or planting of Callery pear trees. Efforts to invoke a statewide ban in Indiana have so far been unsuccessful for fear of economic harm to the nursery trade, but the City of South Bend now prohibits the sale and planting of Callery pear trees, and a future statewide ban is almost certain.

The New Carlisle Olive Township Library is taking steps to rectify yesteryear’s landscaping mistakes. The Callery pear trees around the parking lot developed fire blight this summer, so in addition to the above reasons, the library will remove its 11 Callery pear trees over the next few months. In the spring, they will be replaced with non-invasive, ecologically sound native trees. Removal and replacement will not only increase plant and animal biodiversity on the library’s campus, but also safeguard natural assets, such as the native meadow, and reduce the spread of Callery pears into the surrounding neighborhoods.