October 31, 2014
The Ash trees on the processional allées of the Arch grounds, which are threatened by the invasive Emerald Ash Borer, are being removed. These trees have experienced limited growth over their 40 years of existence from being planted on fill instead of proper soil, being placed in tree pits that limited growth, and being susceptible to air pollution.
The Ash trees will be replaced with London Plane trees, a hardy, disease resistant species that is expected to thrive in this environment. A single species along the processional allées preserves the vision of the park's designers, Eero Saarinen and Dan Kiley, and provides consistency along the allées. The Ash trees will be ground to wood chips by a local eco-friendly company and converted to mulch that will help nourish other trees and landscape in the St. Louis region.
The replacement of the 800 trees along the processional allées is just one component of tree planting on the Arch grounds. Today there are 1,895 trees on the Arch grounds. When the project is complete, the park will contain 4,129 trees, more than doubling the amount of trees there today.
Background: Over a year ago, the National Park Service announced its decision to replace the Ash trees on the processional allées of the Arch grounds with the London Plane tree. The Ash trees are threatened by the invasive Emerald Ash Borer and have suffered due effects of pollution and being planted on fill rather than optimal soil. The decision to remove the Ash trees and replace them with another uniform planting was made after an Environmental Assessment study in 2012 that involved analysis of the Ash trees and public comment. The London Plane Tree was selected after an extensive process that involved input from National Park Service staff and contractors;CityArchRiver design team, the Missouri Department of Conservation, Missouri Botanical Garden, local arborists and nurserymen, and many others.
Trees by the numbers:
Entire Gateway Arch Grounds: Existing trees –1,895 trees
Existing trees to be removed –1,223 trees
Existing trees remaining at project completion –672 trees
Ash trees to be removed along the allées –800
London Plane trees to be added to allées –800
New trees to be added –3,457 trees Total number of trees at project completion will be more than double: 4,129 total trees