Gardening in a changing climate

Central to the High Line’s philosophy is a commitment to environmental sustainability. The park itself is an inherently green structure, transforming a piece of industrial infrastructure into a uniquely designed public space. Our dedication to sustainability is reflected in every aspect of the park’s operation, with the park’s gardens and our horticulture practices, in particular, playing a significant role in our approach to a changing climate.

The High Line’s 150,000+ plants quietly fight climate change and its unpleasant effects for New Yorkers by filtering air pollutants, capturing and sequestering carbon, creating shade that cools the city on hot days, and helping mitigate flooding by retaining stormwater. At the same time, our gardens are providing shelter and food sources for native insects, birds, and other animals at a time when weather extremes and habitat loss mean they have fewer places to go.

The plant species you see on the High Line also have significance in the climate change conversation, differing from more traditional ornamentals in their needs and resiliency. Our horticulturists prioritize the use of native, drought-tolerant, and low-maintenance plant species, which reduce the need for extensive resources. And plants that thrive 30 feet in the air in only 18 inches of soil are excellent examples of resilient species that will survive in the face of a changing climate!

Behind all of these thoughtful, intentional efforts to make our gardens as environmentally friendly as possible is a team of professional horticulturists, led by our Senior Director of Horticulture Richard Hayden. They are helping make the High Line as green as possible—both verdant and eco-friendly (!). And they’re nurturing the next generation of ecologists, horticulturists, and more—whether that’s the visitor casually connecting with our urban oasis and all of its plants, insects, and birds, or a member of our High Line Fellows: Emerging Leaders Program, getting their hands dirty alongside one of our horticulturists.

The climate resiliency of native plants

New York City has a rich botanical history, with plants that have evolved over thousands of years side by side with insects, birds, and other native species that call the city home. Today, the High Line’s gardens include more than 160 species of plants that are native to New York City, including 70 that are native specifically to Manhattan. Choosing native plants is one way our horticulturists build climate resilience in our gardens, decrease the need for resources like water, and support local biodiversity.

Because native plants have evolved in our region, they are well-adapted to the local climate, soil, and wildlife. Their less delicate nature means they’re better able to withstand the temperature fluctuations and periods of heavy rainfall and drought that are becoming more commonplace due to climate change.

What is a native plant?
A simple definition of a native plant is a plant that has been growing in a particular habitat, the ecosystem, or region naturally without human introduction for some extended period of time sufficient to develop complex relationships with other plants and organisms. They are distinguished from cultivars (varieties cultivated by people), naturalized plants (plants that have come to live and spread in an area), and exotics (both invasive and non-invasive exotic species, species that are not native to an area).

Supporting biodiversity in the face of a changing climate

The High Line believes that the significance of our garden goes beyond the 500+ species of plants you’ll find along our park. Together, the plants play a role in the health and wellbeing of our city and its residents—including people and all the wild bees, butterflies, birds, and other wildlife. Cultivating biodiversity and nurturing the larger ecosystem we’re a part of is better for everyone—including people—and is especially needed as the ill effects of climate change and habitat loss create new stresses.

Creating habitats within urban and suburban gardens is a crucial aspect of supporting biodiversity and promoting ecological balance. Habitats provide essential resources such as food, shelter, and nesting sites for a variety of species, including birds, insects, and small mammals. The High Line’s diversity of plant species offers different types of shelter and food sources throughout the year. The park’s trees, shrubs, perennials, and annuals bloom at varying times throughout the year, ensuring a continuous supply of nectar and pollen for pollinators. Our horticulturists also intentionally create resources for beneficial insects and pollinators, like installing bee hotels and water features, leaving leaf litter for insects to shelter in, and cutting back our plants in the spring (rather than in the fall) to allow overwintering native bees to emerge.

During a survey in 2017, researchers with the American Museum of Natural History found 30+ species of wild bees on the High Line. Wild bees—to be contrasted with their domesticated cousins who live in human-constructed hives—are often solitary, making their homes in plant cavities. These bees often have relationships with plants, which have co-evolved over time. Providing a variety of flowering plants for nectar and pollen, as well as a variety of plants for shelter, is key to supporting native pollinators, who in turn support the richness of our ecosystem.

Addressing climate change in the field of horticulture

Our horticulture team consists of 15 professionals who bring together a wealth of experience and knowledge that transcends the level of gardening most of us are familiar with. They see themselves as more than stewards of the High Line’s gardens—they’re stewards of a complex ecosystem that benefits the city and its residents at large.

Beyond the aesthetics, our horticulturists are focused on how to create bird- and insect-friendly habitats, particularly for native wildlife. These efforts go hand in hand with our efforts to encourage and propagate native plants since native plants provide the habitat and food resources that native pollinators and birds need. When selecting new plants to add to the plantings, our horticulturalists look to plants that have proven wildlife benefits, to solve two problems at once—filling a garden design niche, and positively contributing to the existing microclimate. Our team engages with local entomologists, ecologists, and landscape designers to stay as up-to-date as possible on the emergent science of ecologically informed horticulture. To increase the impact of native plants on the High Line and beyond, we’re saving seeds, sharing seeds with other organizations and gardens, and propagating some of our own plants from seed. Our gardens now boast more than 160 plants that are native to New York City, with 70 that are native to Manhattan in particular.

The desire to create pollinator-friendly gardens also impacts how we garden. Following recommendations that came out of a 2017 study with the American Museum of Natural History, we’ve adapted some of our practices. In addition to leaving most plants intact over the winter—which creates food sources and habitat for birds and over-wintering pollinators—we now don’t trim back certain species at all to make sure new bees have a chance to come out of hibernation. You’ll also notice that we leave leaf litter in the planting beds rather than removing it to compost, which creates habitat too. Insects and birds often have niche requirements for food and nesting and living sites, so the High Line’s variety of native plants helps address a variety of needs.

At the same time, we’re always looking for ways to minimize the inputs needed to maintain our garden. We’ve always avoided pesticides, herbicides, and chemical fertilizers, which have known negative impacts on living things and also often use petrochemical ingredients. But we’re also looking for ways to reduce the amount of water we use—by favoring drought-tolerant plants and upgrading to a moisture-responsive irrigation system.

Training the next generation
The collective knowledge of our experienced horticulturists and the complexity of the gardens make the High Line the ideal place for learning. From seasonal gardeners who are getting their start in the field to residents from our High Line Fellows: Emerging Leaders Program, we prioritize training the next generation of professional horticulturists. Stewarding the future of our ecological gardens means stewarding the future of professionals to tend them.

Want to dig deeper into our horticulturists’ work?
Read about lessons learned over the past 15 years of tending the High Line’s gardens in a 2024 New York Times article by Margaret Roach or an interview with arborist Bill Logan and High Line Horticulturist Luka McLean.

Support

This event is presented by Emerson Collective.

The High Line Fellows: Emerging Leaders Program is made possible, in part, by the Jamie and Jeffrey Harris Family Foundation and endowment funds from the Diamonstein-Spielvogel Foundation.