national 9/11 memorial

constitution gardens

ellis island

branch brook park

hoboken pier A park

butternut plaza

more projects, in short



PC+A is honored to be part of the PWP Landscape Architecture and Rogers Marvel Architects team that won the international National Mall Design Competition to re-imagine and restore Constitution Gardens.  

Original designs for this forested passive park were never fully implemented when it was built prior to Bicentennial celebrations in 1976.  Since then, a complex of issues resulted in little public use, little awareness of the memorial’s presence, and severe degradation of the site.  Despite periodic efforts to treat or replant large numbers of under-performing trees over the years, the canopy has not met expectations.

Primary to the trees' problems are the poor, highly variable soils and the site's bowl-like topography. Dredgings and imported construction spoils were used to build the land in an area previously occupied by the Potomic River and the subsequent impact of compaction and poor internal drainage and aeration have inhibited, or even prohibited, root growth and proper function.

Compounding the soil issue is a curious mix of both upland and lowland species resulting from the original planting and subsequent replacement efforts.  Not surprisingly, species with inherent adaptations to bottomlands and floodplains have generally fared better at Constitution Gardens than upland species. Likewise, there appears to be correlation between species performance and elevation, with upland species performing significantly better at the higher perimeter of the site.  Neither of these correlations is perfect, however, suggesting variation in the subsurface soil profiles; further investigation is required to characterize these variations and develop effective treatment strategies.

PWP Landscape Architecture and Rogers Marvel Architects crafted a vision for Constitution Gardens that simultaneously enhances and honors the original design, clarifies the site’s purpose, ensures ecologic health and sustainability, meets modern demand, and provides year-round programming suited to the pastoral setting.

When the project moves forward, PC+A will assist the technical design team in developing and implementing strategies to revitalize the under-performing original planting of 2000 shade and ornamental trees.  Such strategies will include in-situ treatments to improve soil conditions, treatment of tree disease, transplanting of existing trees to more appropriate topographic locations, and replacement with species inherently suited to existing conditions.

For more about the competition and the winning entry for Constitution Gardens, please visit:

The Trust for the National Mall

PWP Landscape Architecture

Rogers Marvel Architects


washington, d.c.


All renderings courtesy of

PWP Landscape Architecture & Rogers Marvel Architects

P1240944.JPG P1240936.JPG

Existing Conditions


Existing Conditions

Existing Conditions

Tree Species All.png Rendering.png

Landscape Architect: PWP Landscape Architecture

Architect: Rogers Marvel Architects

PWP Landscape Architecture  |  Rogers Marvel Architects

© 2014 Paul Cowie and Associates, Inc.