Small pear trees on Lombard Street in Baltimore. by Payton Chung licensed under Creative Commons.

Hot on the heels of the Tidal Basin cherry trees’ peak bloom, a more widespread blossoming is lining DC’s roadsides with puffy white blooms. However, the flowering of Callery pear trees is cause for consternation rather than celebration.

Callery pear trees begin blooming about one week before the famed Yoshino trees. They are currently covered with tight bunches of cream-colored blossoms with faint lime-green undertones from the leaves emerging alongside. Unlike cherries, pear blooms have a notably unpleasant smell, variously compared to dead fish, cat urine, and sex. During the summer, the trees can be distinguished by their glossy, heart-shaped leaves. In the fall, they turn a striking red.

DDOT’s Urban Forestry Administration’s map of where Bradford pears exist as street trees within DC. Read more in their Story Map. Image by DDOT.

The Callery pear tree was brought to the U.S. from central China by USDA scientists to combat a fruit tree disease, but the ubiquitous Bradford variety was invented in Prince George’s County. As Adrian Higgins wrote in the Post in 2018, it was discovered at USDA’s Glenn Dale laboratories by John Creech, a Department of Agriculture botanist, and tested as a street tree in the then-new town of University Park.

Scientists thought the Bradford pear was the perfect tree to match highway-department engineering standards. Its small size means the tree stays out of the way of both fast-moving traffic and overhead electrical wires, and it doesn’t buckle pavements with large roots. It grows readily even in bad soil like red clay shoved aside and squashed by a bulldozer. Pedestrians were likely annoyed that the pears provided little summer shade, unlike the stately but diseased elms they sometimes replaced, but highway engineers cared more about the view for drivers than for walkers.

It’s easy to like — perfectly lollipop-shaped and pops with color in spring, summer, and autumn. It bears tiny, unpalatable fruits that stayed on trees rather than littering the pavement. As the New York Times wrote in 1964, “few trees possess every desired attribute, but the Bradford ornamental pear comes unusually close to the ideal.” Highway departments and developers lined suburban roads throughout the east with millions of these “close to ideal” pear trees over the next few decades.

Pear and cherry trees planted side by side. The pear's branches stay close to the main trunk, in contrast to the cherry's wider spread. Image by Payton Chung licensed under Creative Commons.

A homegrown problem

But soon, the tree revealed its fatal flaws. Unlike traditional street trees like elms, the small pear casts almost no shade on sunny sidewalks. That lollipop shape, reminiscent of architectural renderings, results from what botanists unfortunately refer to as “tight crotch angles.” Its branches fork off the trunk at sharply acute angles, with lots of weak bark rather than strong wood within the joints, making them prone to falling apart in high winds or under ice. They also form spiny thickets that are difficult to remove except by clear-cutting.

The Bradford bore sterile fruits when pollinated by other Bradford pears, but it turns out that it could cross-pollinate with other, newer pear varieties. Those tiny fruits turned pear-lined streets into a bird buffet, and from there birds spread pear seeds everywhere. Millions of hybridized Callery pear trees soon took root anywhere they could find fertile ground and sufficient sun such as roadsides, suburban open spaces, and forest edges. In these environments, the Bradfords displace native trees like loblolly pine, a typical pioneer species for local forest ecosystems.

The highway departments that enthusiastically planted the trees inadvertently created the conditions for them to spread in the clearings along highways and other nearby landscapes. Infrequent mowing gave them a chance to fill entire cloverleaf interchanges before crews could check them.

Pear trees were often planted in the narrow planting strips alongside suburban parking lots, like the trees on the right in this photo taken along Richmond Highway in Fairfax County. In recent years, they’ve invaded unkept areas, like the drainage ditch on the left. Image by Payton Chung licensed under Creative Commons.

A field of invasive pear trees along the Penn Line in Linthicum Heights, MD. Image by Payton Chung licensed under Creative Commons.

Invasive pear trees along Anacostia Drive SE in DC Image by Payton Chung licensed under Creative Commons.

Road-builders have long since moved on from their obsession with Bradford pears, after having picked up too many wayward branches after storms. Many of the early street trees have collapsed on their own, and others have been removed during subsequent streetscape projects.

But Bradford pears are still widely available at retailers and through landscapers, which is why states like Pennsylvania have named them “noxious weeds” and now ban their sales.

Instead of Callery pears, newer varieties of trees have been developed that bear no fruit at all and are stronger against winds. Most landscape experts recommend trees native to the North American landscape such as the redbud, whose purplish flowers are also peaking at this time.

Payton Chung, LEED AP ND, CNUa, sees the promises and perils of planning every day as a resident of the Southwest Urban Renewal Area. He first addressed a city council about smart growth in 1996, accidentally authored Chicago’s inclusionary housing law, and blogs at west north. He currently serves as treasurer of GGWash's Board of Directors.