They have such evocative, pretty names: Porcelainberry, Tree of Heaven, Princess Tree, Bush Honeysuckle.
But they’re bad news for Pittsburgh’s urban forests because they are all invasive species which can cause great harm.
To help the public identify and root out the invasive, non-native species that have taken hold in much of the region’s ecosystem, Pittsburgh Parks Conservancy has created a new guide, “Invasive Plants of Pittsburgh,”
“Whenever you have an invasive plant, it comes from someplace else and it grows in great numbers and often out-competes the natives species — those that are endemic to here — for resources,” explains Pittsburgh Parks Conservancy Senior Restoration Ecologist Erin Copeland.
“That is a problem because the native species are those that feed our native wildlife the best.”
Invasive fruiting plants tend to not be as healthy for migrating birds and breeding birds that live here as native plants are. They also grow so prolifically that they can become monotypic if left unchecked. That means that there would be only one species in the forest, and greater biodiversity equals stronger, more resilient forests.
Invasive species “make our wild spaces less diverse and less able to bounce back from disturbance,” Copeland notes.
The guide focuses on identification of herbs, shrubs, vines and trees and explains how to remove them. Invasive vines, such as Porcelainberry and Vining Honeysuckle, are a particular problem in Pittsburgh.
“They grew up into existing canopy trees,” says Copeland. “And we need our urban forest to provide us with oxygen, filter our air and clean our water.” It’s why the Parks Conservancy staff gives trees a ‘vine haircut,’ cutting the vines at both eye level and ground level to free the tree so it can grow to be healthier, she says.
Plenty of plants are so ubiquitous you may not know they’re invasive. The Callery (or Bradford) Pear, which flowers in the spring and gives off a major stink, is one example.
And Japanese Knotweed is so pervasive because we have similar weather and latitude as in parts of Asia, says Copeland. Plants such as Japanese Knotweed, Chinese Silvergrass and Japanese Stiltgrass flourish here.
“These invasive and non-natives, they’ll never be gone,” says Copeland. “The idea is just to manage them so that they stay in balance with the other plants that are growing in the forest.”
The invasive species guide is available for free online. In addition to helping you weed out anything undesirable in your yard, it can also help you make better decisions at the garden shop.
“One of the most important things is to not plant them,” says Copeland. “Many nurseries still sell invasive and non-native plants. There’s no law that they can’t sell them.”
The guide is designed with volunteers in mind. “You can volunteer with the Parks Conservancy or other nonprofits to take care of our urban wild places,” says Copeland. “We often have people removing invasives and planting native plants and flowers.”
Lately, the Parks Conservancy has employed goats to do a lot of the dirty work, such as a recent project clearing Clayton Hill in Frick Park. Goats will chew through a huge amount of non-native plants in no time.
If you’re considering what to plant in your yard, Copeland recommends visiting the Audobon Society Native Plant Nursery, Tree Pittsburgh Heritage Nursery and Friendship Farms Native Plant Nursery — which all specialize in native plants.
“Our city needs healthy forests so we can live here comfortably, and it’s good for the wildlife,” Copeland says. “We’re not removing invasives just to remove them. We’re aiming for healthy forests and healthy wetlands in the city.”