One of the most pivotal milestones of the High Line’s journey from a derelict railway to a magical garden occurred in 2004, when the world-renowned garden designer, Piet Oudolf, teamed up with landscape architects Field Operations and design studio Diller Scofidio + Renfro to submit a proposal for the park’s design competition. Oudolf’s vision for naturalistic, four-season, perennial gardens captured the spirit and essence of the self-seeded wild landscape that had taken root on the elevated rail track during its years of disuse. Oudolf broke new ground in the field of horticulture with the High Line’s “wild by design” gardens, and continues to provide hands-on counsel today.

Twenty-five years later, the High Line is in the midst of an ambitious multi-year strategic horticulture plan to safeguard our enchanted urban landscape for the next generation of High Line visitors. Piet did us the honor of sitting down with Richard Hayden, High Line Senior Director of Horticulture, to discuss the park’s sustained influence on public gardens, the future and legacy of the High Line, and how a delicate, daily dance between a complex horticultural operation and the formidable whims of nature produces the High Line’s unique beauty.

Richard Hayden: The High Line is an important garden for New York, but I think it’s actually also an important garden for the world. Piet, the whole idea that you introduced that a plant is not worth growing unless it looks good “dead”—the idea of seeds and winter structure—is just such a new concept and so important. The work you did on the High Line fundamentally changed the way people think about horticulture.

Piet Oudolf: When I walked the High Line during the early stages, it was still wild, and I thought, what can I do here? At that time, I was working with the Lurie Garden in Chicago, and we visited many prairies. So, that is where ecology came into my mind as a designer. I started to change my idea about planting design in public gardens, and the High Line let me do something emotionally that had nothing to do with traditional design.

Richard: The High Line has taught people to see and appreciate the beauty in the dormancy of the gardens—that’s a big change that the High Line introduced to the world. But now, one of the trends we’re seeing is that the naturalistic style has been embraced. These more naturalistic gardens and meadows have gotten very popular, and one of the problems is that people are embracing this style of planting, but they don’t have the skills to take care of it. So we need to build more education around how to steward these kinds of naturalistic gardens.

Piet: I think it’s the most complicated thing to understand a garden. Traditional gardens in public spaces are built and maintained by contractors. So what [the High Line does] is exceptional. It’s an example of how it could be. So culturally, it’s really important for people to see gardens like this. Public gardens are examples of how you can create parks or public space in cities, in environments where they are seen by millions of people.

Richard: And they don’t just see it—they feel it. They also get to be a part of nature, and they see the way the wind blows in the garden, and the insects and the bees and the butterflies, so it becomes a real experience in nature.

Piet: It’s a big stage for how we could imagine being in nature. But nature is so complex and not always nice. So, because of the High Line, that education is happening. What we try to do is to get people interested, we show them that you could do a garden in a more interesting way, in a more sustainable way, in a more complex way, and in a more diverse way.

Richard: That complexity and diversity is a lot of work. Cultivating a wild, naturalistic landscape actually requires meticulous, painstaking work and maintenance, as well as specialized expertise.

Piet: The complexity is so high that you need a team of people who understand it. You need a base team of people to teach others, to bring people in, and to let people learn. I think if you lose the gardeners, you lose the garden.

Richard: We did a calculation recently, and we think it’s about almost four acres of actual garden. And when you think about having 10 full-time horticulturists taking care of four acres, that’s a very high ratio. But, we take great pride in our care of the garden, so it’s important to have all that staff.

Piet: These beautiful plants are put together in a way that looks wild, but it is kept by gardeners who understand plants and know their plants. That is key, otherwise you can’t do it. That’s why there are so few of these examples of these kinds of gardens. There are not many gardeners with skills like those at the High Line. Because you can only achieve what we do at the High Line when you create a team with the same sort of language, the same sort of feeling, the same sort of will to keep things going.

Richard: And I always say that a lot of what we do is kind of manage plants from swallowing other plants. For a plant to be successful 30 feet in the air and in 18 inches of soil, it has to have a certain amount of aggression, a kind of will to survive.

In the fall, we were editing out some of the perennials that had gotten a little too numerous. Your design uses some big prairie plants, which are meant to be more of what you call scatter plants, and you have a matrix of grasses and things that are kind of the ground cover of interest. Sometimes some of those scatter plants, like New York ironweed, get too numerous. We did some fall planting in September, putting in some more grasses to be more in balance with all of the perennials.

We replanted the big bog this year because of the horsetail, it just took over, and we just had to start from scratch. And I think the soil needed a refresh. It’s looking really beautiful right now.

Piet: Gardens are allowed to change. Trees grow. For me, plants are personalities, plants have character. You put them on stage and have them perform. So a garden is not only a sort of community of personalities that like each other, it’s also a sort of stage play. We are not creating wilderness. We are creating gardens. The High Line is one big garden, so we have to see plants as having a personality—otherwise, you cannot put them in the right place. You have to think of a garden as a community and plants having companionship.

Richard: When you first start out to make a list of plants for a garden, are you thinking about a plant that has four-season interest and then kind of dialing back with flower color?

Piet: With every garden, before I create a palette of plants for a particular area, I think of it as a painting, but a four-dimensional painting. Few plants have four-season interest, but it should have more than just flowers, so the seed heads are important. You may have a plant like a geranium that flowers in spring, but becomes a good ground cover in the fall. They have interest in spring, but texture in the fall and winter. North American plants that flower in August will have seed heads that birds can pick from, so that gives you summer and fall. It’s not about all plants having all four seasons. It’s about all plants having another function other than just the moment that they are in flower.

Many of the plants need to be sort of generalists, plants that will live in half shade, or not too dry or too wet. When you’re planning gardens, it’s not about all the plants you can use everywhere. Over the years, because there’s so much more stress from roots from the trees and shrubs underneath, you have to replace them many times. And so every plant plays its own role in the garden and it needs its own place in the garden and at the same time, it has to look good. So it’s quite a complicated matter to explain why you do things as you do them and why some plants are higher in the hierarchy than others.

Richard: And then you’re combining those to come up with the four seasons.

Piet: Yes. For example, the interest in geranium is very small, for a very short period of time. So it flowers, and then it’s just there. So another plant takes over the place of the geranium, and at the same time, the geranium becomes your ground cover.

Richard: It almost feels like you’re conducting an orchestra. You have the plants you need at the very beginning of the song, and then the music swells, and you’re just always looking for something else to provide—

Piet: That is your stage play. There’s a beginning and an end, but there’s no pause, and in general, it should be good for the eyes. Some places look more interesting in spring than they do in fall, and then the trees become more important, and the fall colors of the trees are more visible and take the lead. So that is how it should be.

Richard: Sustaining the gardens through 15 years of a changing climate and neighborhood has not been without challenges. Because of the buildings that have sprung up next to the High Line, we’re now looking at too much shade. Or, we have to deal with the sun angle changing with new buildings, and we get scorching, we get reflected light. That’s something that some of the plants are not happy with. So we’re constantly having to rethink. Some of the gardens are based on new construction. They put up tall buildings on the south side of the 30th Street garden, so it’s all going to change. We’re still struggling with that. When there is construction, the construction sheds that get put up shade out a portion of the garden and there can be compaction. I don’t know where the weed seeds come from, but they come, and so that’s one of the other things. When you’re not doing regular maintenance, and there’s construction going on, you have to rebalance the garden.

Piet: It’s very difficult. The buildings changed everything on the High Line—the planting, the atmosphere, the climate. So it’s not the garden itself, but everything that happened around it. But that is what makes it necessary to take action.

Richard: Maintaining biodiversity and pollinator habitats is also a priority. We did a study with the American Museum of Natural History back in 2017 that looked at the wild bees on the High Line, and that helped inform how we garden.

We’ve changed some of our Spring Cutback [ link to Spring Cutback page ] techniques based on knowing that we’ve got native bees that are using some of the perennial and grass stems for nesting. But it’s funny—to make wildlife habitats happy, you would be doing nothing. You’d be leaving all the leaves, you wouldn’t be cutting back. And so it’s finding that sweet spot for really representing this beautiful urban horticulture, while still managing to do what you can to support some of the bees and the other things that are visiting. I always say, with biodiversity, it is about species support, and humans are one of those species that we’re supporting. And so having this really emotionally evocative garden for them to engage with is another one of the things that we do to serve biodiversity.

Piet: If you do it right with your planting, there will be pollinators. There will be birds, there will be insects, there will be mice. There will be things you don’t like. It’s a whole world in itself. But if it doesn’t appeal to people, if people don’t like it or don’t feel anything, the High Line wouldn’t exist. So putting in this extra emotion into the work of gardening is important, because if the plantings weren’t interesting, we wouldn’t have the status of a garden, we’d have a park that nobody would look at, that’s a gym where people ride bicycles.

Richard: I always say that the High Line is the most important public garden of the 21st century, because it changed the way we think about gardens. I think the legacy of the High Line is that The New York Times called you, Piet, the most famous living landscape designer, and they called the High Line your most famous work. The High Line is a world treasure, and I don’t say that to brag. I say that because we feel a tremendous amount of responsibility to maintain it. Looking forward into the next 15 years, the future holds some daunting challenges as well as some incredibly exciting opportunities.

For example, we’re reconstructing the Western Rail Yards’ walkways and furniture, and we’re in conversation with you to design a new entrance garden at 34th Street.

Another thing that we’ve started is soil testing to really understand what we need to do to keep the soil healthy. Because obviously, if you want healthy plants, you need healthy soil, and we’re using a kind of constructed soil, so that has its own limitations. And we want to understand what fertility is and soil life. So we’re going to be looking at that as we kind of look to the future as well.

Piet: We designed [the High Line] without knowing what it would become. I think even the architect and landscape architect had no idea what it would be for the city. I think it was more of a neighborhood garden that turned into a worldwide, well-known, renowned garden. What do we think about it? I don’t know. The future is in the hands of gardeners, in the hands of people like you, Richard, and my future is reacting to their questions.

The High Line is a very important garden to me, but it is also a very garden for New York. So that’s why we should keep it going—not only for ourselves, but also for the city.

Get an insider’s look at the gardens during this conversation with the visionary behind the park’s four-season garden design, Piet Oudolf; author and photographer, Ngoc Minh Ngo; and High Line Senior Director of Horticulture, Richard Hayden.