Invasive plants threaten Pa. parks

Joe Napsha
| Monday, Aug. 12, 2013, 12:16 a.m.

In stifling summer heat, Pia van de Venne is digging, ripping and stacking pieces of a sprawling, green-leafed shrub consuming a Murrysville hillside.

She's fighting an enemy she knows she can't conquer.

“We're trying to keep the invasive plants out of Duff Park. We can't beat it, but we're trying,” said Van de Venne, president of Friends of Murrysville Parks.

On this day, she battles multiflora rosa — a flowering shrub introduced from Asia in the late 1860s — that grows so rapidly and densely that it chokes out native vegetation and hinders nesting birds, according to the National Park Service.

Van de Venne's story is one of dozens playing out across Pennsylvania, from Ligonier and Crafton to Upper Darby and Doylestown, as communities try to stem the spread of non-native, invasive plants such as multiflora rosa, bamboo and Japanese knotweed. They grow wildly, buckling patios, sidewalks and curbs, creeping into basements and engulfing just about anything in their paths.

“It is a serious problem. When the invasive plants move into native plant areas, they take away the habitat and resources — the light, nutrients, soil and water — that are part of the sustaining ecosystem,” said Cynthia Walter, associate professor of biology at St. Vincent College near Latrobe.

Plants that take hold are difficult and costly to control, said botanist Andrew Rohrbaugh of the state Department of Conservation and Natural Resources.

“They tend to take over a lot of the habitats,” Rohrbaugh said.

Invasive plants that do nourish birds and animals tend to have fruit inferior to the quality of native species, he said.

The state, with the help of ecologists and other natural-resource partners, listed 79 herbs, vines, trees, shrubs, aquatic plants and grasses deemed as invasive. Twenty-five trees, grasses and bushes made a “watch” list, meaning they eventually could threaten ecosystems.

In the world of invasive plants, a rose is not always a rose.

“One person's decorative plant is another person's problem,” Walter said. “What is the definition of a weed? A plant in a place where you don't want it to be.”

Along the Kiskiminetas River, Japanese knotweed consumed almost 90 percent of the banks, environmentalists say. The knotweed can stand 9 feet tall, forming a canopy with leaves the size of an elephant's ears that smother native vegetation.

Knotweed fluorishes along shorelines, railways and highways, Rohrbaugh said.

Dave Beale, watershed specialist for Armstrong County Conservation District, called it a “never-ending fight” to eliminate the plant.

Although some plants clearly are undesirable, others become so only decades after their planting.

As land use and climate evolve, plants become unwanted.

That's the case in Murrysville, where callery pear trees embellish commercial and residential properties.

Mayor Robert Brooks asked owners who planted the flowering trees to replace them with a friendlier species, such as Hawthorn.

“If we can have more people understand the value of having native plants, then they'll get a better feeling why we want to do this,” he said. “With the native plants, you get the native birds, the native animals. It's really back to our roots.”

In Ligonier and Crafton, bamboo is the culprit.

Leslie Nemeth wants to eradicate a neighbor's golden bamboo coming into her Ligonier backyard.

“It is under my steps, it is under my flower bed, it is under the brick sidewalk that is in the center of my backyard. It will soon make it into more invasive areas, like the sewer or the pipes,” Nemeth said.

A borough council committee will draft an ordinance addressing the planting of bamboo.

In Crafton, borough council acted swiftly to prevent the spread of bamboo and other invasive plants. Officials took their cue from the state by banning every plant on the list of invasive plants.

Residents who don't comply with the ordinance can be fined.

Yet cutting down bamboo won't stop its spread, said Caryn Rickel, president of the Institute of Invasive Bamboo Research in Seymour, Conn.

The running bamboo, a hardy plant that can survive cold winters, can be difficult to detect because it hides underground as it spreads, moving about 20 feet a year, Rickel said.

“One plant will go nine miles. This is giant timber bamboo. It can be 45 feet high and 8 inches in circumference. It kills all other plants,” Rickel said.

The way to stop its spread is to burn the plant's rhizomes, underground stems that produce shoots and roots, Rickel said.

“The longer you wait, the harder it is to get it out. It gets stronger every year,” Rickel said.

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