For landscape architect Jennifer Horn of Horn & Co., the success of a project on a tight lot in Northwest Washington turned on the fate of a century-old sycamore tree. The specimen rose between two recently joined properties, each boasting a house designed by architect Carmel Greer—a stone residence with a deck and pool, and a redwood guest house on the adjacent lot. Working with landscape contractor Justin Spittal of Planted Earth, Horn merged the two into a cohesive family compound through the use of unifying landscape elements.

The entire site measures less than a quarter-acre—and the goal of saving the sycamore was paramount. Horn designed a gravel terrace for the guest house around the roots of the tree. From there, stone-slab steps traverse the one-time setback zone between the houses, crossing the property line close to the tree. A retaining wall continues the original property line, framing an outdoor kitchen that faces the pool. Formal steps lead to the lawn and a second deck.

“The properties together have a homogenous feeling,” says Spittal. “Yet there is still some delineation.”

Natural and machine-cut stones mingle amid native ferns, grasses, red twig dogwood and a weeping redbud tree. “I wanted it to be clean and clear,” Horn notes, “but also organic.”