The garden on Whitehaven Street is not the only example of an English-inspired landscape in Richard Arentz’s prolific portfolio. In fact, the landscape architect’s own country home in Fauquier County, Virginia, is a charming homage to the famous British poet and plantswoman Vita Sackville-West.

“I love the British landscape school,” Arentz admits.

What sets the Whitehaven property apart, and the factor that drove this elegant, English-accented design, is the authenticity of its neighbor: Britain’s ambassador to Washington occupies the residence on the other side of the back fence. It is there that British royals unpack their bags when passing through the capital. In fact, it was just such an occasion that led to a spruce-up of the ambassador’s garden, which compelled Arentz’s clients to reinvent their own space.

As Arentz recalls, the ambassador’s gardener removed a stand of bamboo, which had provided a great deal of privacy. As a result, Arentz’s clients were inadvertently exposed to the sight and sounds of traffic on the busy stretch of Massachusetts Avenue known as Embassy Row. The owners had always appreciated their picturesque view of the ambassador’s brick chimneys atop the only home designed by British architect Sir Edwin Lutyens in the United States. But their once-pleasant landscape, complete with a swimming pool and mature saucer magnolia trees, no longer provided a refuge.

Arentz took a practical approach to the problem. “Could we block Massachusetts Avenue by building a conservatory in the garden?” he asked. “And could we create a water feature with sound to mitigate noise?”

In the spirit of invention, he then turned to the site itself. With some artful foreground plantings, the British ambassador’s landscape could offer a view to “borrow,” a design tradition as time-honored as Lancelot “Capability” Brown, the visionary 18th-century British gardener.

“My clients didn’t have a huge garden, so we needed to ‘borrow’ the view,” Arentz explains. “We try to do things that are very specific to the site, and it’s an incredible fortune to visibly ‘borrow’ from the landscape of the British ambassador’s residence in Washington.”

Inspiration for the water feature came directly from a Lutyens-designed estate in Hampshire, England, known as Marshcourt, which was planted by British horticulturist Gertrude Jekyll.  Like the terrace at Marshcourt, the Whitehaven garden is largely given over to a rectangular sunken fountain-cum-koi pond, which replaced the existing pool. Steps leading down to the water on all sides add a sense of depth. As at Marshcourt, the terrace surround, which combines smooth and textured French limestone, incorporates planters into the stonework.

“You’re drawn out by the verticality and down by the depth,” Arentz explains. “It really does pull you out there.”

In his design of the elegant conservatory, Arentz responded to another challenge common to the few remaining residences in a neighborhood popular with embassies: The eastern side of the garden was exposed to the Brazilian Embassy. By siting the conservatory at right angles to the house and fountain, Arentz effectively masked the nearness of the distinguished neighbor.

The freestanding structure features a fireplace embedded in a wall of teak and a greenhouse extension for orchids, a gardening passion of the homeowner. The conservatory quickly became a sought-after library, refuge and dining space. Automated shades, operable windows and a “serious” air-conditioning system combined with radiant heating in the limestone floor enable year-round use. A full basement beneath was carved from the deep end of the former swimming pool.

“It’s built like an incredible European car,” Arentz explains, pointing out that unlike wooden structures that expand and contract with changes in humidity, “The conservatory is extruded aluminum, so there is no movement.”

Signature details that appear in Arentz’s portfolio—including discrete reflecting pools, restrained use of sculpture, clipped hedges and climbing vines that soften masonry façades—are all in evidence on Whitehaven Street. The site benefitted from existing Southern and saucer magnolias, holly and boxwood, some transplanted or enhanced. In the northwest corner beyond the fence line, a weeping cherry on British soil serves as a dazzling backdrop to the owner’s saucer magnolia when the two species bloom simultaneously in spring.

Beyond a low yew hedge, the shrub border was pumped up with bottlebrush buckeye, mahonia, photinia, rose of Sharon, dwarf forms of summersweet and leucothoe, native azalea and a fragrant Korean spice viburnum. For ground cover, ferns—Japanese-painted, autumn and cinnamon—blend with epimedium, hosta and Japanese sacred lily. A single-tree peony with spectacular golden-yellow blooms enhanced by crimson centers provides the ultimate experience of rare and fleeting beauty.

“I mix plants quite a lot,” Arentz says of seeking seasonal and textural variety. “I also think about scale in the space and creating a framework for the garden.”

Eventually, the owners sold the property, and it now serves as the Embassy of Sri Lanka. But Arentz still considers Whitehaven to be one of his favorite projects—as much for his accommodating clients as for the neighborhood. Now, in addition to the borrowed view, the British and Sri Lankan neighbors share a passion for tea.

Conservatory Design & Landscape Architecture: Richard Arentz, ASLA, principal; Patrick Carter, AIA, conservatory project manager; Michael Rossetti, RLA, project manager, Arentz Landscape Architects LLC, Washington, DC, and Marshall, Virginia. Conservatory Contractor: Keller Wintergardens, Luxembourg; and Lofgren Construction, Gaithersburg, Maryland. Exterior Lighting: Outdoor Illumination, Bethesda, Maryland.