Part of the New York City Park Experience: Joining the War on Invasives

It’s on the walls of brownstones and train stations and in New York City parks. And it isn’t mold—it’s English Ivy. 

A non-native plant, English Ivy (Hedera helix) outcompetes native flora and fauna for vital resources, degrades habitats and disrupts delicate ecosystems.

Recognizing the threat, the Prospect Park Alliance hosted an invasive species removal event in June to promote ecological stewardship in Prospect Park, Brooklyn’s 530-acre backyard that draws in over 10 million visitors a year. The group’s volunteer event “Park Pitch In: Invasive Species Week” mobilized New Yorkers to be community caretakers. 

 “Our volunteers are crucial to maintaining the health of our park,” said Erinn White, the alliance’s project development coordinator. “Without them, the park would be in a lot worse shape.”

White and the alliance’s landscape management team, armed to battle scourges of invasive invaders like Mugwort and Goutweed—and English Ivy, of course—took full advantage of the more than 20 volunteers that signed up, teaching them how to spot, remove and eradicate invasives, all in the most eco-friendly terms.

English Ivy, a popular green vine turned widespread ecological threat, was originally introduced to North America by European colonists as early as the 1700s. People initially admired its resilient, evergreen leaves, seeing it as an easy-care solution for ground cover and adding old-world charm to gardens.

By the 1820s, it was already a common site in New York City’s refined landscapes, chosen for its ability to thrive and low-maintenance appeal. However, this “carefree” plant soon proved otherwise.

It spread aggressively and quickly escaped the confines of gardens. Birds, drawn to its berries, inadvertently spread seeds far and wide into natural areas like Prospect Park. 

This combination of intentional planting and accidental dispersal laid the groundwork for a modern-day ecological problem.

Once unleashed, English Ivy transforms into a relentless competitor. It blankets the ground and forms dense webs that stop sunlight and nutrients from reaching native seedlings and understory plants, creating “ivy deserts.” 

More alarmingly, its climbing vines can often be seen swallowing mature trees, blocking their leaves from the sun and adding a considerable weight, making the trees vulnerable to storm damage. 

That’s where the Prospect Park team fits into the landscape. The project coordinators and volunteers help craft a battle plan against invasive species.

By picking and pulling for up to two hours, the team also uses the green space as an open-air classroom, particularly for first-time participants who may not have a background in plant identification or even know what a healthy plant looks like. 

To bridge this knowledge gap, the coordinators offer photos to volunteers or drop to the ground to show them the actual plants, helping volunteers to learn through direct observation.

They also demonstrate identification methods based on the appearance of unique leaf characteristics, and occasionally, sensory cues like smell or touch.

Alliance members say this hands-on guidance ensures that every volunteer, regardless of his or her experience, leaves with a deeper appreciation for the park’s ecological challenges and the skills to contribute effectively.

Removal Techniques

The landscape management team uses a variety of eco-friendly techniques to combat invasive species and restore the park’s natural landscapes. 

Each member is a “subject matter expert” for the park and has particular skill in restoration, ecological health and industry practices. Each method is based on the park’s specific needs.

To remove English Ivy, Mugwort and Goutweed, volunteers removed weeds and composted them on-site using a technique called “dead hedges.”

Dead hedges are built to compost organic material directly within the woods, and also guide park visitors to stay on designated paths, which maintain the health of the ecosystem.

Volunteers reinforced existing dead hedges by adding downed limbs and branches, then placed the removed weeds on top to decompose naturally. 

The landscape management team also opts for other specialized techniques like solarization, a longer-term effort to use the sun to do the dirty work with invasive plants. The team covers specific areas with clear or black plastic sheeting to trap solar heat, and essentially “cook” the unwanted vegetation and their root systems. 

 “Often, the invasive plants that are targeted would be nearly impossible to eradicate using traditional manual methods. Solarization is an opportunity to reclaim small target areas, causing less disturbance and, eventually, a lot less labor,” said Mary Keehbauch, deputy director of the landscape management team.

After a period ranging from several months to up to two years, the solarization process is complete, leaving the soil ready for new native plants.

In the winter months, sheet mulching is used. Sheet mulching is a weed-suppression method that creates a barrier to prevent weed growth while enriching the soil. It involves layering cardboard and organic materials over an area to smother invasive species plants and promote decomposition. 

First, the invasive species and roots are cleared from the area. Then, a layer of cardboard is laid down to fully cover the soil, followed by a layer of freshly fallen leaves collected from the park. By the spring, these layers begin to decompose, creating a nutrient-rich base. 

Holes are poked through the cardboard to plant new native seedlings, which benefit from the lack of weed competition and new mulch. 

This technique has been used at the LeFrak Center at Lakeside in Brooklyn for preparing spring plantings.

The Future of Prospect Park 

Beyond organized volunteer events, the Prospect Park Alliance encourages all park-goers to practice “park champion” behaviors. These simple stewardship actions include staying on designated paths, observing plants and wildlife from a safe distance, and properly disposing of all trash. 

The alliance has designated July as “Lake Appreciation Month,” celebrating Brooklyn’s only freshwater lake at the heart of Prospect Park. 

“I’m always blown away by the dedication of our volunteers,” said White, the alliance’s development coordinator. “We have groups of people from all walks of life, and they work together seamlessly. They have fun.”