Wolfgang Oehme and James van Sweden / Photograph © Volkmar Wentzel, ca. 1990, courtesy The Cultural Landscape Foundation

The default American landscape before game-changing landscape architecture firm Oehme van Sweden & Associates (OvS) came along was a great expanse of lawn, really an ecological wasteland, with perhaps a fringe of flowers. But all of that changed with James van Sweden and Wolgang Oehme’s New American Garden style, which burst onto the scene in the early 1960s. A new exhibition at the National Building Museum (NBM) in Washington, D.C. honors this still-evolving approach inspired by Native American landscapes. As NBM explains, “the New American Garden is characterized by large swaths of grasses and fields of perennials.” The style re-creates the seasonal splendor of the American meadow while “celebrating its inherent ecological, sustainable, aesthetic, and ornamental values.” Eric Groft, FASLA, a principal at OvS, one of the firm’s second generation leaders, added…