Prospect Park is home to Brooklyn’s last remaining upland forest: more than 30,000 trees of more than 175 species that keep our air clean, provide shade and cooler temperatures on hot summer days and a haven for wildlife year-round. In the face of climate change and a number of insects, diseases and other stressors, caring for this Brooklyn treasure is a constant focus of the Alliance’s Landscape Management team, who make use of a number of innovative strategies to help the trees of Brooklyn’s Backyard continue to thrive for generations to come.

Prospect Park’s beloved grove of nine American Elms (Ulmus americana) near Dog Beach on the Long Meadow are getting some much needed tender love and care thanks to the Alliance’s Landscape Management Team. These trees, which are close to 100 years old, are a Brooklyn treasure. Recently, the team injected the trees in the grove with an immunity-booster, known as “inoculant“, to protect them against Dutch Elm Disease, a fungus that has devastated this species of trees across the country for over 50 years. “The inoculant makes its way all throughout the tree in only about a week,” shares Alliance Arborist Malcolm Gore. “Trees are always moving fluids throughout their systems internally, so the dose spreads like a slow and steady drip. Much like how we protect ourselves from disease, one dose is not sufficient for a lifetime, and just as we need booster shots regularly, so do these trees. Providing this boost gives our trees the best chance they have to continue thriving from the inside out,“ says Gore.

Elm grove vaccination in-progress in the roots of the nine American Elms in the grove this Spring.

The team was also strategic in timing this work. “We did this in the Spring because that’s when trees are moving energy up to their leaves, which makes it a great time of year to ensure the full tree is protected.“ Disease spreads when the carrier feeds on an infected tree; for instance, a beetle will suck on the sap of a tree, and if that tree is infected, that beetle spreads the disease to the next tree, making it essential for the entirety of the tree to have this layer of protection.

In addition to proactively immunizing the tree against Dutch Elm Disease, the Alliance’s Landscape Management team is also giving the grove some much needed rest and relaxation, including temporarily fencing off the area in order to aerate the soil around their roots to address compaction from years of heavy use. “Giving these trees the break and the rest that they need is what allows the trees to be here for such a long time. With healthy soil quality, these trees can live for up to 200-300 years and will remain a vital part of our park and community for centuries to come,“ shares Gore.

The American Elm Grove in Prospect Park c. Martin Seck

Another tree under threat in the park are the Beech trees (Fagus grandifolia and Fagus sylvatica), due to a relatively new disease aptly called Beech Leaf Disease. Jumping into action at the first sign of this disease in the park, the team plans to use phosphite, which acts as a Vitamin C-like immune booster to strengthen the trees’ immune response. A practice long used in agricultural settings for orchards and for crops, the team will use a phosphite “basal bark drench,“ which involves spraying the bark at the base of the tree. Since Beech trees have a very thin bark, in a matter of only a week or two the “booster“ travels from the roots through the entire tree to protect it against disease.

While the team takes on these interventions, they pay close attention to the fact that disease alone is only one factor that contributes to a tree’s health. Soil compaction, drought and extreme temperature changes are also increased threats. In the face of new tree diseases and ever-changing and unpredictable environmental factors from climate change, it’s all the more important to be intentional about our planting for the future of the park. 

The Alliance is in the midst of a large fall planting season with 9,000 trees, shrubs and herbaceous plants. “We’re planting a diverse range of species, and ones that can withstand the changes in our environment,“ says Gore on the ways the team remains adaptive and forward-thinking. “Last September we saw six inches of rain in a day and this year we will be lucky to get an inch in the whole month. Planting with climate change in mind is not just about planting more warm-weather species, but also considering the extreme variabilities in weather we are getting year to year. We cannot rely on historical data as much any more for expected precipitation and temperature ranges. We’re focusing on planting the types of trees that can adapt and survive through the extremes.“

Learn more about the park’s 30,000 trees and how you can help keep them green and vibrant with every visit.

This work was made possible through generous funding from the New York State Department of Environmental Conservation Urban and Community Program and the NYS Environmental Protection Fund, which has enabled essential tree maintenance in Prospect Park.