Solar Innovations Take On Invasive Plants

Have you spotted plastic tarps in certain areas of the park and wondered why? Fear not–they’re not picnic remnants or litter left behind. The tarps are an eco-friendly approach to fighting invasive plants without the use of harmful chemicals. It’s just one of the many ways that Prospect Park Alliance’s Landscape Management team has deployed environmentally friendly and innovative approaches to keep the park’s natural areas green and vibrant; including the use of goats to clear invasive weeds, ladybugs to tackle a harmful insect infestation, and layers of cardboard and mulch to ward off opportunistic plants of concern.

This season, the team has been hard at work implementing a technique called solarization to help keep the park’s landscape healthy and resilient with strategically placed sheets of plastic.

Solarization at work at the Children’s Pool in the Northeast corner of Brooklyn’s Backyard. Photo courtesy of Mary Keehbauch.

The team charts out a customized approach based on the specific needs of each landscape. “The plastic color and thickness is determined by the location and the target plants. Is it sunny or shady? Upland or near the watercourse?  Is it a small enough area that we will be successful with this method? How will it look or impact the experience of park users?” says Mary Keehbauch, Prospect Park Alliance’s Deputy Director of Landscape Management, on the meticulous planning behind this method. “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.”

Because of these shrub stumps’ location at the top of a steep slope, the team used solarization to avoid destabilizing the slope with digging. Photo courtesy of Mary Keehbauch.

At the onset, solarization is an intense labor of love and requires an area to either be completely cleared of all organic material, or in the case of the tall reeds near the lake, flattened with plywood. “Thankfully, we have very willing and devoted volunteers and staff that help prepare and install the appropriate type of plastic,” says Keehbauch. Thanks to the hard work of these staff and volunteers, native plants have been successfully reintroduced to the south Lakeshore area and parts of the Lullwater.

The solarization of a given area can span anywhere between two months to two or more years, and, while restoration will be ongoing, this technique has already helped slow the growth and minimize the presence of invasives in the park. Once an area is cleared or flattened, the team uses either black or white plastic to reap the benefits of solarization. Black plastic is used to block light and heat the roots of an invasive plant once it has been cut down, while clear plastic is used in areas of direct sunlight to stop the plant’s growth, heat up the soil to destroy the roots and rid the soil of any remaining seeds. The end result is soil that is ready to be planted with native, pollinator-friendly plants that will help Prospect Park’s ecosystem thrive.

The technique is currently underway in multiple areas in Brooklyn’s Backyard and is focused on suppressing Amur Honeysuckle (Lonicera maackii), Goutweed (Aegopodium podagraria) and Common Reed (Phragmites australis). All three of these invasive plants spread quickly and form dense clusters that can outcompete and eventually replace the park’s native plants. This work allows native plants to grow and thrive, which promotes the longevity of Prospect Park’s landscape and helps protect the habitat of the countless wildlife that call the park home.

Keep an eye out for the innovative ways Prospect Park Alliance works to tackle invasive plants throughout the park and learn more about how the Alliance is sustaining the environment.