London Planetree Selected to Replace Rosehill Ash Trees on Gateway Arch Grounds

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Date: May 29, 2013
Contact: Kathy Schneider, 314-655-1630

An Environmental Assessment (EA) was completed in 2012 which examined the vulnerabilities of the current ash tree plantings to a destructive insect, the Emerald ash borer. It determined that the best course of action was to remove the single species planting of Rosehill ash trees and replace it with a new uniform planting using a species compatible with the initial design intent of this National Historic Landmark. The criteria included looking at the various species advocated by the original landscape designers, Dan Kiley and Eero Saarinen, as well as other species that met their initial goals of providing obvious, grand processional walkways leading to the Arch. Other criteria included form, resistance to disease and pests, availability of numerous cultivars, and adaptability to soils present on the Arch grounds and urban living conditions.

During the evaluation process, the final list was narrowed down to the Gingko (Gingko biloba), Tulip poplar (Lilodendron tulipiferous) and the London Planetree (Platanus acerfolia). The London Planetree was selected as it is pleasing in appearance, with smooth trunks and exfoliating bark, can survive in the alkaline soils of the Arch grounds, and there are a number of cultivars available that are resistant to diseases and insect pests. The tree is one of the most highly suited to tight allée plantings, creating arching, cathedral-like spaces, while its overall form will complement the ascending quality of the Gateway Arch. The London Planetree shares similar characteristics with its parent, the native Sycamore tree, which grows in abundance along the Missouri and Mississippi River floodplains, as well as the smaller creeks and tributaries across the state. This hybrid tree was developed prior to the year 1700, probably as a cross between the Native American sycamore and the Asian planetree. Historically, it was the second choice of Kiley and Saarinen for the allées. 

A key feature of the historic landscape, the allées of trees along the processional walks are by design composed of a single species of tree, and amount to roughly 45% of the total plantings on the grounds. Rehabilitation of the processional walks, a primary component of the CityArchRiver 2015 project, includes the Rosehill ash tree removal and subsequent replacement by the London Planetree. In addition, the project will remove barriers to accessibility and improve subsurface soil and drainage conditions that exacerbate the decline of the allée plantings. The tree replacement and walkway rehabilitation work will be funded through a mix of public and private sources. 

The National Park Service is proposing action at this time due to the current state of decline of the Rosehill ash trees as well as the impending arrival of the Emerald Ash Borer in the St. Louis metropolitan area. The Rosehill ash is a species that is susceptible to ash borer damage, and it is anticipated that once these insects become established in the St. Louis area, the ash trees will succumb to them. In addition, the existing ash trees, many over 40 years old, have reached or passed their maturity due to urban conditions, and need to be replaced regardless of the ash borer. The Memorial's General Management Plan directs park managers to protect the allées along with the other character-defining features of the National Historic Landmark. These features are part of the design plan for the grounds created by Dan Kiley, noted modernist landscape architect and close friend and frequent collaborator of architect Eero Saarinen. Saarinen himself worked closely with Kiley on the landscape plans for Jefferson National Expansion Memorial, and the Memorial staff and preservationists within the NPS have made great efforts to preserve the landscape in the form as closely approximating the original plan as possible.

The Gateway Arch and the Old Courthouse are part of Jefferson National Expansion Memorial, located on the riverfront in downtown St. Louis. The Old Courthouse is open daily year-round from 8 a.m. to 4:30 p.m. The Gateway Arch is open daily from 9 a.m. to 6 p.m., except during the summer months, when extended hours are 8 a.m. to 10 p.m., from Memorial Day weekend through Labor Day. The Gateway Arch and the Old Courthouse are closed Thanksgiving, Christmas, and New Year's Day. All programs are FREE of charge and open to the public. Programs and events at the park are made possible by the generous support from our cooperating association Jefferson National Parks Association and Bi-State Development Agency. For more information about programs and events, please call 877.982.1410.

Last updated: April 10, 2015

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