Nearly two decades ago, Kathryn Herman—a high-flying American landscape designer with round-the-world clients—spent a transformative week in England’s Somerset County, taking in the genius of husband-and-wife horticul-turalists Sandra and Nori Pope, creators of the acclaimed gardens at Hadspen House. “They are colorists, and I was hugely impressed by the subtle gradations they had established,” Herman recalls. “And I said, that’s what I’m going to do for myself when I get the opportunity.”

The Popes had transformed 18th-century Hadspen House’s huge, dilapidated potager into dynamic color-themed gardens that bedazzled novelist and gardener Jamaica Kincaid, who once wrote, “Nothing matched in a way that I understood.”

But after the Popes decamped to their native Canada in 2005, their landlord bulldozed the couple’s Arcadia to make way for a new garden—which, ironically, was never planted.

The Hermans’ house is a former groom’s cottage at Connecticut’s legendary Pepperidge Farm. Neil Landino Jr.

The garden’s floral compartments are separated by flying buttresses of shaped beech. Neil Landino Jr.

Hadspen’s glories may be gone, but an echo can be found at Herman’s Connecticut residence, the remodeled groom’s cottage of a 1920s estate. There the designer has installed “a garden that is as true to an English-style garden as I can make it.” That would be a 114-foot-long garden room, packed with perennials and backed by mature trees, among them the pepperidge trees that gave the property—and original owners Margaret and Henry Rudkin’s famous bread business—its name.

“A garden room is a wonderful thing—it’s embracing, it’s structure,” says Herman, who tours English gardens every year with James Doyle, her coprincipal at Doyle Herman Design Associates, for ideas. “And if you don’t have structure, what do you have?” A tall beech hedge defines Herman’s garden room, which has been subdivided by flying buttresses, also of beech, into compartments that shelter flower beds. The dense greenery, sheared once a year to keep it tidy, recalls similarly architectonic enclosures at Staffordshire’s Biddulph Grange and Warwickshire’s Coughton Court.