Preserving the urban canopy

Benjamin Franklin Parkway

The Benjamin Franklin Parkway is one of the most historic and beloved boulevards in Philadelphia, lined with iconic buildings and renowned art collections.

The Parkway also features artistic works of a different, greener, kind. London plane trees, dating back to 1917—when the Parkway was originally constructed—rim the nearly mile-long stretch. Interspersed among those trees stand red maples, sweet gums and red oaks, added more recently by the Fairmount Park Commission to diversify the Parkway’s leafy canopy.

A team based out of the Morris Arboretum is helping to protect and enhance the overhead greenery as street-level renovations move forward, including the improvement of traffic lanes, an upgrade in sidewalks and curbing, and the installation of new benches, bicycle lanes and pedestrian crossings.

“We’ve been involved ever since there was the idea in Philadelphia to restore the Parkway,” says Jason Lubar, associate director of urban forestry at the Arboretum. “Early on in the Parkway renovation, it was realized that trees play an important role as part of the design element. As the Parkway has aged, so have the trees that were originally planted there.”

The Urban Forestry Consultants team has inventoried most of the trees along the Parkway, and will provide expert opinion on how to minimize the impact of construction on the avenue’s elder hardwoods and softwoods.

In its 15-year history, the Arboretum’s Urban Forestry team has worked on a variety of projects and initiatives, from Washington, D.C. to MIT. They have conducted arboriculture workshops and seminars, performed safety inspections on trees to assess the damage of cavities, cracks, fungal fruiting bodies and other signs of structural problems and used computer-based mapping to collect information on canopy size, tree type and life expectancy.

Currently, the team is working with the TreeVitalize project, supported by a sizeable grant from the William Penn Foundation, to replace the declining tree canopy in southeastern Pennsylvania. The team is also adding street trees as part of the Baltimore Pike revitalization in Lansdowne, East Lansdowne, Upper Darby and Clifton Heights and is partnering with Fairmount Park to identify and remove hazardous trees.

The team also provided Narberth Borough with a GIS-based street tree inventory, outlining specific tree care needs, a customized tree ordinance and a tree management plan with a proposed budget for deferred and ongoing maintenance.

But the biggest project for the Urban Forestry Consultants has been the work along the Parkway. Beginning in 2004, the team partnered with the Pennsylvania Horticultural Society and the City of Philadelphia to assess the aging paulownia trees around Swann Memorial Fountain in Logan Circle.

Lubar explains that some of the trees surrounding the fountain had to be removed because of defects that would have likely caused them to die in the near future. As a result of their recommendations, the aged trees, ranging up to 50 feet tall and about 63 inches in diameter, were removed and new pawlownias were planted.

The challenge—as with any big renovation project—was in balancing the safety of the community members with their love for the individual trees. “They were cared for over the years [but] were just getting old,” says Lubar.

“We’re experts,” he adds. “We’re just looking at the trees and providing our non-biased opinion. We provided a report that guided decision-making.”

More recently, the team collaborated with OLIN Studio and the Pennsylvania Horticultural Society to preserve trees in the Rodin Museum garden during a museum facelift.

“The original garden was growing old and the trees were large and they were looking to restore the garden to what it was like when it was put in,” Lubar explains. When it became clear that the museum's restoration activities would impact some of the existing trees, Lubar and his team found a way to protect the existing canopy, using an air excavation tool to expose the tree roots without harm. “We helped them find a way to preserve the hardscape and the trees.”

Lubar, an International Society of Arboriculture Board Certified Master Arborist who has worked at the Arboretum for more than a decade, says caring for trees in an urban environment presents special challenges.
“Trees evolved in the woods and we’re putting them now with cement mulch around them, with soils that are very different from where they evolved,” he says. “There’s always a challenge keeping trees healthy in the urban environment.”

For more information on the Urban Forestry Consultants, go to www.morrisarboretum.org.

Originally published on October 29, 2009