Angora goats trim weeds in the Wissahickon.

by Lou Mancinelli

For the past three years, goats have contributed to battling invasive species in the Wissahickon Park at different times. Yes, goats – like free-range landscapers.

In 2012, the herd battled a bamboo plot in the Andorra Natural Area. The year before that, they tried garlic mustard at Longwood Gardens, which they didn’t like. And in 2009, the goats enjoyed meadow grasses, thistle, and honeysuckle at Bartram’s Gardens in Southwest Philadelphia.

During the past three years, the project has assisted the Friends of Wissahickon (FOW) develop alternatives for combating invasive species in the park and beginning to think about developing a larger plan for that work.

“If we’re going to apply goats in a bigger setting,” McCarthy said, “what could our strategy be?”

In the Wissahickon, the landscaping skills of Rodin, Wyeth, Kandinsky, Caravaggio, Goodwin and Andy Warhol – a herd of six woolly angora goats – were pitted against the work of human volunteers and herbicides in a contest to see what method worked best. A 20 by 20 foot plot was designated for each technique.

While the results from the contest still have to be analyzed by botanists, what became clear is that perhaps the best way to develop a plan for reducing invasive species in the Wissahickon might be a combination of humans, herbicides and alternative means – like goats.

“What we found is it wasn’t about the volume the goats would eat,” Post said, “but what they would eat.”

What the goats eat depends on the species of the weed and time of year. In the spring they will pass right by mile-a-minute weeds, Post explained, but in the fall when the weed is mature the goats love it. Especially the seeds.

In the Wissahickon, in June, the goats devoured oriental bittersweet and wing-stem burning bush. In August, they took to English ivy and privet. But their privet pulling was second to the picking abilities of humans. The grazers also loved poison ivy, which, though it is a native species, can become a problem and is a weed humans tend to avoid.

“They will reach up as high as they can on the trunk of the tree to eat poison ivy,” said Yvonne Post, a food educator and owner of Cooking For Real, as well as the owner of the herd. Post brought the goats to the Wissahickon in the back of a Subaru from her farm in Chester County.

One thing this experiment, which first started as a non-scientific alternative approach in 2011, has showed, according to McCarthy, is that goats can never replace the importance of human judgment in terms of what to pick, and the effectiveness of thumbs.

Goats can go in and eat an acre of poison of ivy, but they “can’t clear selectively,” Post said. That’s where humans come in.

After leaving the Wissahickon this August, Post, and her daughter Deirdre Sheehy and the herd, embarked on a cross-country sustainability voyage to spread the word about goats’ weeding abilities and to raise awareness about sustainable approaches to preservation of open space. It’s a project called The Bellwethers Trending Toward Sustainability, which can be followed on their blog of the same title.

As of mid-August, the gyspy-like crew were in Missoula, Mont. Since they departed the Wissahickon, they have traveled through Ohio, Wisconsin, Minnesota, South Dakota and Montana on their way to a new home at Post’s farm in Oregon.

“Out west this a normal thing,” Post said. She said she wanted to introduce the alternative to the Philadelphia scene. She first acquired the goats in 2008.

The first two years of the project in the Wissahickon served as a test period that measured the goats’ effectiveness. At the start, botanists from Bowman’s Hill Wildflower Reserve cataloged the findings. This year was more of a public outreach campaign to introduce the work to the public and put the herd in more visible areas in the park. The hairy foragers even put in a stint along Forbidden Drive.

Invasive species can negatively impact open space by undermining its ecological system. They can begin to challenge native root systems, which sustain local wildlife. Almost every time there is a major rainstorm in the area, the Wissahickon looks like a kid who got beaten by a bully.

Many native plants are eroded by the storms, and Invasive species can grow in their place as well as other places, and begin to establish a monoculture – an unhealthy situation for an open space.

“When you have an out of control single species, goats are great at [removing] that,” said Maura McCarthy, FOW executive director.

For example, there’s about a 50-acre stretch of knotwood along the Cresheim Creek that goats could go at like gas-free weed whackers. But a project like that, according to McCarthy, might require as many as 20 to 40 goats a few times a year. And it would likely have to be boer goats, which are larger and less finicky than the angora breed. For that, Post said Brian Knox of Eco-Goats in Maryland is the go-to person.

Still, the goats are an attractive alternative and a good way to capture the public’s attention to raise awareness about invasive species, and how each of us might affect the ecological health of an open space.

“They are adorable while eating things,” McCarthy said. “That’s a talent.”

Any plan that involved goats would have to be well-designed. One issue that makes it so you cannot just send in the goats and sit back and wait for them to do the work, is that when you remove an invasive species, you have to replace it with a native species, according to McCarthy. What species you can plant depends on the terrain. The terrain in the Wissahickon is a constant recipient of behavior that challenges its normalcy. Therefore, its management is a constant issue.

“The park is a complicated chain of interrelated systems,” McCarthy said.

It is subjected to high and heavy water flow, deer predation, people and pets dumping non-native species in its parts, changing soil composition and human use that may seem minimal but has a noticeable impact. Plus there are the homes that surround the park.

“Animals and plants that make a living in this park don’t see the boundaries,” McCarthy said, referring to where the park ends and where homes begin.

Moving forward, McCarthy said there would likely be discussions between FOW and the city’s Parks and Recreation Department about what a plan with the goats might look like. That could mean the goats might be unleashed at targeted areas during certain times of the year, a few times a year, to munch on a specific weed.

In Philadelphia and across the country the woolly grazers have become one way people are supplementing their campaigns to support the ecological health of open spaces.

In June 2011, New York City officials turned 20 goats loose in a phragmites-ridden Staten Island wetlands they plan to turn into a park, according to a 2012 Philadelphia Inquirer article.

In September 2012, Chicago officials issued a request for bids for a herd of grazers to clear overgrown areas of O’Hare International Airport, the article said.

In Southern California, where brush-fed wildfires run free, goats are often used to clear up timber. They have been deployed at Google’s Northern California headquarters and at the historic Vanderbilt Mansion in Hyde Park, N.Y., according to the Inquirer.

In the next year or so, FOW will also work with Parks and Recreation as it develops a citywide forestry management program. That could mean using the landscaping grazers in some way in the future.

To cover the cost, FOW would launch a public fund-raising campaign. So far, the FOW has not used the entire $3,000 budgeted for the grazing munchers, which indicates the project is an affordable one.

For more information about the free-range goat landscaping efforts in the Wissahickon, visit For more information, and to follow the progress of Post’s goats as they cross America visit

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