Morris horticulturalist works to save Wissahickon, wetland

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Pam Morris’s title at the Morris Arboretum is horticulturalist, but a more accurate description of what she does might be “natural areas manager.” Morris, an environmental scientist who joined the Arboretum staff four years ago, splits her time between the Wissahickon and the Arboretum’s own wetland.

Both projects extend the Arboretum’s commitment to preserving the natural environment, within its gates and beyond.

In the Wissahickon, Morris is working to restore a section of woodland along the Thomas Mill Ravine. Down by the creek, near the red covered bridge, Morris and volunteers—“from the Sierra Club, boyscouts, Hebrew School, I’ll accommodate anyone”—have done work to restore a meadow. Most of the restoration, though, has taken place at the top of the hill where Chestnut Hill Avenue meets Seminole Street. There, Norway maples had been crowding out the native plants.“It’s an exotic invasive species,” explains Morris, with a longer growing season than other trees. “It holds its leaves longer and shades out the native plants.”

As well as being a “water hog,” the Norway maple’s leaves also contain a “latexy” substance that, when the leaves fall, creates a mat that is difficult for seedlings to work their way through. Morris and her crew have been removing the offending trees and replanting with native oaks, beeches and flowering trees. Closer to home, Morris has been working to return a section of the Arboretum to its original wetland state. When the Morrises lived here a century ago they drained the wetland—located to the right of the main entrance on Northwestern Avenue—to use it for pasture land. In the intervening years, says Morris, some of the drains failed and “wet, seepy areas” appeared.

By linking the wet areas together, Morris and her team created a shallow lake (above), which they planted with pin oaks, river birches, willows, chokeberries and herbaceous plantings such as grass and an aquatic plant known as a “duck potato.”

“Based on the hydrology,” says Morris, “it made sense to return it to wetland.” And because the area sits on a flood plain, “When it floods now, instead of rushing over the meadow, it retains water and lets it go back down slowly. The plants themselves slow the water and hold the soil.”