The purple flowers all over Philly trees can eventually kill them

Romanticizing life is easier when purple flowers make traveling around Philly feel like a scene from Bridgerton. But captivating things can be treacherous.

Enchanted by these blossoms, a reader asked Curious Philly, The Inquirer’s forum for questions about the city and region: What are all the beautiful trees with lavender-colored flowers that are seemingly all over?

They are not actual flowering trees, said Andrew Bunting, vice president of horticulture at the Pennsylvania Horticultural Society. They are wisterias, ornamental vines that grow up trees, creating the impression of fragrant flowers that bloom with spring.

As with many species, wisterias have multiple types. American and Kentucky wisterias are native to the United States, but they are unlikely to be the ones Philadelphians are seeing on trees, Bunting said.

The sweet-scented purple fluffy flowers are most likely Japanese and Chinese wisterias, both considered invasive.

“It’s highly, highly unlikely that if they have a wisteria growing up their tree, that it’s the native one because the native one doesn’t occur naturally,” Bunting said. “They are invasive plants choking a 100-foot-tall tree, and probably eventually will contribute to its demise, and ultimately to its death.”

The non-native status doesn’t mean these deadly beauties are new to the Philadelphia scene. They have been here longer than cheesesteaks.

Both the Japanese and Chinese wisterias arrived in colonial times, Bunting said. In those days, they were considered rare, leading folks to plant them in arbors, pergolas, and trellises for their ornamental beauty. Over the decades, inadequate maintenance led to seeds making their way into other residential areas and the woods.

Bunting has noticed a wider spread of these two types of wisteria in the last 20 years, which might be why more Philadelphians are seeing them.

The weather and reproduction could be reasons, he said.

“Maybe it’s just a better spring for whatever reason, and maybe there’s more flowers,” Bunting said. “Or it’s becoming more obvious because there’s more of it in the woods.”

Whatever the case, prevention is no longer an option to stop trees from being fatally decorated by these wisterias. Trees and bushes that have them will be slowly smothered at different paces depending on their size. Bunting recommends removing them — by cutting the wisteria trunks that are climbing up the tree at the base — or judiciously pruning them to slow their continuous expansion.