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Plant of the Week: Compass plant

During September, Friends of the High Line is celebrating the Chelsea Grasslands – a special area of the park between West 18th and West 20th Streets that was inspired by the tallgrass prairie of the American Midwest. As part of the celebration, we're featuring plants and trees from the Grasslands throughout the month.

Difficult to miss this time of year, Silphium laciniatum has a bright yellow flower with lengthy stalks. Often mistaken for a sunflower, both are members of the Asteraceae family but are of different genera. This long-lived perennial blooms July through September and can reach a lofty height of 6-10 feet. In the High Line's shallow beds, Silphium laciniatum cannot stay upright on its own, so it tends to spread over its neighbors or along the railing of the park.

In a natural setting, the plant stays firmly upright, and is considered a prairie landmark that competes against other giants such as big blue stem. The plant's roots can reach an impressive depth of 15 feet, a characteristic that allows it to survive the severe droughts and wildfires common to its native prairie.

Photo by Ayinde Listhrop

Silphium laciniatum is distinguishable from other silphiums thanks to its leaf characteristics- they are hairy and rigid, described as sandpapery, and lacerated or deeply cut, often compared to the shape of a pin oak leaf, but much larger. A second silphium is planted in the Chelsea Grasslands- Silphium terebinthinaceum, or prairie dock- but its leaves are heart-shaped and entire, its stems and bracts are smooth, and it manages to stay upright in the garden more often than not. The Missouri Conservationist magazine says "compass plant leaves are like prairie dock leaves that someone went after with a pair of scissors," so differentiated and deeply lobed is S. laciniatum versus S. terebinthinaceum.

The common name of Silphium laciniatum is compass plant, a nickname that originated from the north-south orientation of the plant's leaves. This orientation reduces the amount of solar radiation leaves soak in during the day, therefore maximizing water efficiency. Supposedly the leaves will remain cool to the touch due to this orientation, even on a hot summer day. The predictable orientation of the leaves also allowed compass plant to act as a navigational tool for pioneers, who could orient themselves based on the direction the leaves faced. Additionally, pioneers marked wagon routes by "tying scraps of cloth to the tall stems to indicate safe passage around boggy swales and sloughs," according to John Madson in Where the Sky Began.

With the decline of the prairie habitat, compass plant populations have also declined. Livestock decimate Silphium populations when allowed to overgraze, and continual mowing or plowing generates a similar level of destruction. Aldo Leopold compared the severe decline of the buffalo to the decline of the compass plant: "Few grieved when the last buffalo left Wisconsin, and few grieve when the last Silphium follows him to the lush prairies of the never-never land." Only through thoughtful and extensive restoration efforts may we perhaps replicate the conditions Silphium laciniatum requires.

PLANTING TIP

Compass plant requires lots of space, particularly vertically. If you have the space, it is recommended to plant by seed rather than cutting or transplanting because of the extreme depth of the tough taproot. The plant will not bloom until the second or third season, perhaps even the fifth or sixth according to some gardeners. Compass plant is extremely drought tolerant and disease resistant, and is a great choice for disturbed areas, naturalistic gardens, and restoration sites.

WHERE TO FIND THIS PLANT

10th Avenue Square at West 17th Street and the Chelsea Grasslands between West 18th Street and West 20th Street

The High Line's planting design is inspired by the self-seeded landscape that grew up between rail tracks after the trains stopped running in the 1980s. Today, the High Line includes more than 500 species of perennials, grasses, shrubs, and trees – each chosen for their hardiness, adaptability, diversity, and seasonal variation in color and texture. Some of the species that originally grew on the High Line's rail bed are reflected in the park landscape today. Every week we share one of our gardeners' current favorites with you.

Our horticultural team counts on members and friends like you to help keep the High Line beautiful and thriving. Join our community of supporters who play an essential role in the High Line's most important gardening projects.


Celebrating the Chelsea Grasslands is made possible, in part, by TD Bank—the Presenting Green Sponsor of the High Line.

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