Ask a Gardener

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Our High Line gardeners are a great resource for information about the High Line's landscape, and the unique challenges of tending a garden in the sky. Now, we would like to share them with you! Go directly to the source for any planting-related questions by emailing them to gardener@thehighline.org.

Please be sure to include your name and city along with your question. If selected, the answer to your question will be posted on this page. Please note: due to the high volume of questions we receive, we are unable to answer every question.


Can you tell me a good time to see the most wildflowers blooming on the High Line?

Sue, New York City

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The High Line is designed so that there is seasonal interest all year round, from the early blooms of the witch hazel in February to the late blooming asters that lasted until November this past fall. In the winter, winter berries and bloodtwig dogwood provide great color contrast against the snow. Right now, we have a beautiful display of bulbs and spring ephemerals, with new additions every day.

One of my favorites that is about to bloom is the shooting star, (Dodecatheon meadia). However, the most flowers are probably in bloom in June and July, from the purple prairie clover (Dalea purpurea) to the rattlesnake master (Eryngium yuccifolium). You can also purchase a plant guide from our online store, which has photos, locations, and cultural information about our most popular plants.

Be sure to come visit often, something new is in bloom every week!

- Maeve, 04/22/11


I am wondering if a field guide is available?

Christine Moore

A lot of people ask about a field guide or plant list. In fact, we have both! Check out the Design section of our Web site.

You can download our entire plant list, as well as more specific lists that tell you what's in bloom in each area of the park each month.

Additionally, we now have a seasonal field guide with plant information, pictures of our most popular plants, and a map of where they can be found in the park. The latest Plant Guide is available from the High Line's Web Shop, and the Fall guide is on its way.

Thanks for writing!

Maeve - 08/24/10


How ecologically friendly is the High Line? Are you using unnatural chemicals? Are any of the species being planted non-indigenous/invasive species? Are you going to encourage animal life as well as plant life (birds, chipmunks, etc.)?

Matt Arguin

Great question. One of the main principles we strive to live by up here is sustainability. To fertilize our plants, we use compost tea — a concoction of compost, natural fish fertilizer, and food for bacteria and fungi, such as molasses or flour — all brewed together overnight in an aerated brewer to promote microbial growth.

As for plant selection, we look for species that come from places that make them suitable to the High Line's unique cultural conditions. About 50% are plants native to North America, and about 30% are native to the Northeast. We also have a lot of cultivars (cultivated varieties) of native plants, and a few plants native to Europe and Asia.

We are all keenly aware of keeping invasive plants off the High Line. As gardeners, we know how much trouble they can be in a garden. As an organization, it goes against our principle of helping to restore the native ecology of the area. Which brings me to your question about animal life. What we have found is: if you build it, they will come. We have already seen a wealth of birds embracing the High Line and the new food source in Manhattan! We've spotted juncos, song sparrows, catbirds, house sparrows, robins, barn swallows and a few warblers. There are even a few Peregrine Falcons who are nesting nearby, though we haven't seen them land on the line yet.

Don't forget — the High Line is inherently a green roof, which also helps reduce the amount of storm-water runoff, as our planting beds absorb a lot of water that would otherwise run directly into the sewer system.

Read more on our Sustainability Page.

Thanks for writing!

Maeve - 08/13/10


Are there any flowering plants or unique species that will thrive or "show their colors" in the cold weather?

Alf, New York, NY

This is a great question. There are several special plants on the High Line that we're really looking forward to watching this winter. Some, such as Ilex verticillata, Cornus sanguinea 'Midwinter Fire', and Viburnum bodantense 'Charles Lamont' are already "showing their colors", and the witch hazel, Hamamelis x intermedia 'Pallida', will bloom soon as well.

Ilex verticillata 'Winter Red', or winterberry, is a deciduous holly native to the north east United States. There are several of these Ilex growing in the Gansevoort Woodland. They're the shrubs with bright red berries covering the twigs. In addition to being a cheerful bit of color in the landscape, the berries provide food for birds overwintering in the neighborhood. This plant was recently featured in the High Line blog post Holly on the High Line.

Cornus sanguinea 'Midwinter Fire' is a red twig dogwood cultivar named for the color of it's winter bark. Our Midwinter Fires are planted in the beds around 10th Avenue Square. The twigs will continue to blush prettily until the plants begin to leaf out in the spring.

Another plant growing in the Gansevoort Woodlands, Viburnum bodnantense 'Charles Lamont', is currently the only plant blooming on the High Line. These viburnum have clusters of pink to white fragrant flowers that are so special and welcome in the middle of winter. They'll be followed shortly by the Hamamelis x intermedia 'Pallida' planted in the Washington Grasslands near Blaichman tunnel. These shrubs will have spidery, yellow flowers with a sweet, unmistakeable witch hazel scent, usually by February.

There are lots of other plants on the High Line that were chosen not only for their spring and summer flowers but for their interesting structures, shapes, colors and textures in the winter landscape. The birch trees have their signature winter-white bark. The little bluestem grasses have gone from blue-green to rusty-pink. The seed heads of the echinacea are still prominent and still attracting birds. The fruits on the smooth sumac are, as one visitor said, like "clumps of fuzzy, garnet colored caviar". Some of the cool season grasses like the Sesleria autumnalis "greened up" late in the fall and are looking vibrant even now.

Hope this answers your question, and I hope people will brave the cold weather to visit the High Line all winter. There's still so much to see up here!

- Andi, 12/30/09


I have not known any indigenous birch trees anywhere in NYC. Was there ever a time when they were native to the City?

Jean, Hopewell, NJ

Betula populifolia, or grey birch, which grows on the High Line, is native to the north eastern United States along with several other species of birch. Researchers with Brooklyn Botanic Garden's New York Metropolitan Flora Project, http://www.bbg.org/sci/nymf/, have sighted Betula populifolia growing in King's county before and since 1980, though not in large populations. I also checked the Manahatta Project website- http://themannahattaproject.org/home/. According to their research, birch trees, including Betula populifolia, were probably growing on the island of Manhattan in 1609, before Europeans ever set foot here.

Other birch trees native to the area include Betula lenta (sweet birch) and Betula papyrifera (paper birch).

Thanks for your question. I always love an excuse to do some plant related research!

- Andi, 12/29/09


What are the flags in the ground for?

Patrick, Queens, NY

While walking on the High Line, you may encounter gardeners marking plants with little colored flags. The gardeners are mapping the planting beds and counting the number of a particular plant species in a given area, which is made easier by using the flags. Now that the first season for the plants on the High Line is coming to an end, we want to make an inventory by verifying how many plants we have of each species and where exactly they are growing. Many of our grasses and perennials are self-seeding and will tend to multiply on their own over time, gradually changing the appearance and composition of the plantings. Though we welcome the evolving plant numbers, our hope is to preserve the original design intent and to do so, we plan to keep a close eye on our records of what plants, and how many, are growing on the High Line.

- Kaspar, 12/2/09


Are these the plants that were here before the High Line was a park? Are all the plants on the High Line weeds?

Katie, Brooklyn, NY

No. Every plant that you see in the park was specifically selected for the park and planted here. When we first started construction, we had to remove everything from the line in order to remove environmental contaminants, install a drainage system, and waterproof the structure. Many of the plants that you see were selected to evoke the feel of the overgrown tracks. Some plants are the same species as what grew on the tracks previously, while some are related to what grew here or have a similar form and feel, and while they may seem wild or untamed, they are not weeds. We do get plenty of weeds here, just like every other garden, and spend many hours dutifully pulling them.

- Maeve, 12/2/09


How deep is the soil?

Rick, New York, NY

The soil depth differs throughout the High Line. In general, it is about 18 inches, though it reaches about 36 inches where there the large trees have been planted in the Gansevoort Woodlands and 10th Avenue Square.

- Maeve, 12/2/09


Does the High Line have an irrigation system?

Salmaan, New York, NY

Yes, we have a combination of drip irrigation and pop-up sprinklers throughout the planting beds, as well as plug-in water valves spaced every 60 feet that give us the ability to hand-water areas as necessary. The irrigation system is supplemental – it alleviates the need to hand-water entire beds.

- Kyla, 12/1/09


What happens to the plants in the winter?

Michelle, Brooklyn, NY

All of the herbaceous plants on the High Line are perennials that are considered hardy in our climate. This means that they go through a period of dormancy, or rest, during the winter but will come back the following spring. In many gardens, old stalks, leaves, and spent flowers are removed or cut back in late Fall. At the High Line, we will take a different approach by leaving plants in place. Visitors will have a chance to notice the plants’ winter interest with their unique seed pods and fruits, intriguing winter forms, and evolving fall and winter season colors. In the early spring, the herbaceous material will be cut down in preparation for the new growth that will begin again, and the trees will flower and leaf out (though not necessarily in that order!). The autumn is also important for root development. While it may look like the plants are not growing, there is always something happening within the soil!

- Maeve, 11/30/09