Within a few years, the company became known internationally for its radically different approach to landscape design — replacing staid evergreen hedging, bedding annuals and groomed lawns with broad sweeps of long, flowering perennials and ornamental grasses.
The vision was a rejection of passive vegetative architecture in favor of the bold massing of grasses and perennials that placed the observer in the midst of a living tapestry. The result was a garden that actively responded to light, wind and seasonal change. “They move in the breeze and sparkle like stained glass,” he stated in “Gardening With Nature” (1997), one of five books he wrote.
The look became known as the “New American Garden” and seized the imagination of clients and the design press with its associations with the prairies of Mr. van Sweden’s native Midwest, as well as the grass gardens of progressive designers in Oehme’s German homeland.
The duo’s work ranged from private homes, including Oprah Winfrey’s, to major public spaces such as the National World War II Memorial on the Mall and the Nelson A. Rockefeller Park overlooking the Hudson River in lower Manhattan. Locally, the firm did work at Reagan National Airport, the Martin Luther King Jr. National Memorial and Francis Scott Key Memorial Park in Georgetown.
In 1990, the late landscape architect John O. Simonds described their work as “unlike anything yet seen in America.” It presaged today’s emphasis in landscape architecture on naturalistic and ecologically sensitive design.
“People without knowing it were thirsty for a change,” said native plant expert and designer Darrel Morrison, explaining the immediate appeal of their work. “It was a reaction to the dullness of the designed landscape at that time.”
From the beginning, Mr. van Sweden advocated his style in even small urban spaces as a way of capturing the natural exuberance of the prairie and meadow. He also espoused the idea that gardens should be planted for year-round interest.
The design partners set out to prove their theories — and win clients — by converting the deep but narrow backyard of Mr. van Sweden’s Georgetown rowhouse into a space layered with grasses, perennials and small trees in a way that blurred boundaries and paths. The object, Mr. van Sweden wrote, was “to lead the eye deeper into a scene which is not completely revealed, even in so tiny a space.”
“I think the two of them really did help to accelerate the recognition that the landscape of the city is a planted, managed, dynamic and changing landscape,” said Gary Hilderbrand, a partner of Reed Hilderbrand landscape architects and Harvard University adjunct professor of landscape architecture.