If the Sky is the Ceiling

The right combination of plants creates lovely alfresco architecture.

By Marion Butterworth

Photograph courtesy of John Shorb Landscaping Inc.

Suburban sprawl takes on a whole new meaning as living space spills into the great outdoors. Instead of thinking of the yard as space to outfit, like a house with weather-resistant furniture and acclimatized art, imagine that the sky is the ceiling, lapped by a canopy of leaves supported by stately columns of trees. In these outdoor rooms, fireflies are lamps, banks of plantings form walls, hedges delineate space, and groundcovers serve as dense, spongy carpeting. In the hands of skilled landscape designers, natural architecture can completely replace the manmade kind.

Shaping an Outdoor World

Before decorating your alfresco “building” with colors of flowers and foliage, you must define the structure itself. The most basic and essential elements of any architecture are walls and walks.

Using plant material to structure outdoor spaces is not a new concept. The Romans cultivated hedges of myrtle, laurel, and boxwood. They are credited with introducing boxwood, the classic, slow-growing plant that defines English knot gardens, to Europe in the 14th century. European colonists used walls of living shrubs not so much for privacy, as we do today, but more to define the boundaries of their domains and to protect them from beastly marauders, both four- and two-legged. Long before the advent of the quarter-acre suburban lot, feudal lords managed tracts so vast that fencing them was impossible. Simple, naturally occurring hedgerows of diverse species identified boundaries of fields, pastures, and homesteads.

Hedging Your Bets

Although hedges have evolved into important aesthetic components of contemporary landscapes, they remain true to their archetypal functions. Hedges clearly say, “Mine,” but with more polite elegance than a truculent two-year-old.

Like a motel with a perpetual vacancy, they offer room and board for birds and bunnies, inviting wildlife diversity while dispelling any doubt as to how the hedgehog got its name. They offer a buffer from winds and noise, decrease soil erosion, obscure unpleasant views, and guard against unwanted attention.

“Hedges can serve a number of very useful roles in the garden,” says Nadine Horenstein, a division manager of John Shorb Landscaping Inc. in Kensington. “They can help define a garden’s boundaries, giving a ‘garden room’ a sense of place in the landscape; they can provide crisp, clean lines within a garden; or they can be a more natural, free-form border.”

Whatever the use, hedges appeal to the senses in a way fences cannot: They grant a garden color, texture, movement, and fragrance. Living walls are the architectural building blocks of the landscape. They help divide and conquer vistas. Garden designers report that many clients don’t realize that a framed view can be more pleasing than an open panorama until they see that principle put into practice.

The style of a landscape can also depend on its hedges. For instance, walls of deciduous shrubs such as bridal veil spirea, forsythia, hydrangea, mahonia, and wild roses imbue the spring garden with a romantic, informal look. Differing heights in hedges of mixed species such as viburnums, barberries, hawthorns, and beech create a wild, rustic feel.

For suburban settings, Horenstein recommends informal hedges such as cherry laurel, nandina, photinia, and azaleas. In landscapes with a more buttoned-up demeanor, boxwoods, yews, privets, and hollies can be crisply clipped into geometric shapes with sharp edges.

Chevy Chase Challenge

One of Shorb’s clients in Chevy Chase envisioned a formal yet lush landscape to complement the front of their newly renovated home. “We wanted a kind of English look, very neat and formal,” the client explains. She and her husband found the balance of symmetry and the precision of a well-manicured lawn appealing. Ideally, their new landscape could be maintained to highlight these features.

To reinforce the shape of a new, winding path that leads to the front door, they requested a low evergreen hedge. Shorb landscape architect Sarah Davis selected extremely cold-hardy Hoogendorn holly, which resembles boxwood and takes well to shearing. She knew it could be trained to mimic the curves of the path and circle the “meet and greet” ring in front of the house. Its small leaves, dark glossy green with slightly scalloped edges, provide a sharp contrast with the light-colored pavers of the walk.

Like a flattop haircut, hedges demand regular trims to maintain crisp edges throughout the growing season, about eight months long in the metro area. The homeowners appreciate the way Shorb Landscaping maintains the design, never allowing bushes to outgrow their space, block a window, or overshadow another plant.

Green Screens

To separate the Chevy Chase homeowners’ front yard visually and physically from its neighbors, Davis designed layered plantings along the left property line. She added American hornbeams, handsome understory trees belonging to the birch family, whose slender, zigzagging branches make an attractive silhouette in winter. The hornbeam’s common name, “musclewood,” aptly describes the trunk and larger limbs, which look like sinewy, flexed muscles. Well suited to the homeowners’ preference for a tailored style, the hornbeams sport flat crowns that can easily be kept in check because these trees respond well to heavy pruning.

Near the street, in front of the hornbeams, mounds of Virginia sweetspire anchor the bed. Banks of Otto Luyken laurels grace the mid-ground with deep evergreen leaves. In the springtime, their fragrant white flowers bloom alongside the pink blossoms of the neighboring Yakushimanum rhododendrons, which flower in May. Drifts of Hardy Gardenia Azaleas and pockets of sweetbox join cotoneaster to form the third and lowest tier of the screen. One of the very few plants that flowers in the dead of winter, sweetbox announces its presence with a haunting perfume. “It makes going to get the newspaper a treat,” the homeowner remarks.

Although the plant materials Davis chose for the screen are varied, grouping like plants together keeps the design formal and controlled. “The more formal the landscape, the less mixing [of plants]” is her guideline. When the screening needs to be taller, Davis’ favorite choices are large evergreens–Leyland cypress, arborvitaes, Nellie Stevens holly, and Japanese cedar.

From the Ground Up

When a Northwest Washington homeowner requested an overhaul of her existing landscape, Davis used dwarf mondo grass to cover the ground in her Landscape Contractors Association award-winning design.

“We wanted a softer, more welcoming look,” the homeowner says of areas formerly beset by overgrown boxwoods, hollies, and azaleas. The fine texture of the dwarf mondo grass allowed the introduction of contrasting plants, including skimmia, nandina, hellebore, hosta, and Golden Hakone grass, whose silk-like leaves droop toward the ground, evoking images of a small waterfall.

Davis was playful as well as practical in this design. “Sometimes it’s fun to have plants interspersed with others, like hosta coming up in clumps through dwarf mondo grass,” she says.

Realizing the importance of accessibility to this new outdoor room as well as its need for order, Davis also created a path. A landscape exists in chaos if not for transitions from one area to the next. Where no walkway or sense of entrance existed, stepping stones now march through the shade garden, extending an open invitation. Their placement and composition are perfect, as they blend in seamlessly yet still lead the eye and persuade visitors to stop and look at all the right spots.

What’s underfoot is just as important as the larger plants in a landscape because garden visitors interact intimately with the things they brush against or tread upon as they move through the space. Accessorizing paths with groundcovers like dwarf mondo grass makes the journey as enjoyable as the destination and can also unify divergent components, making them the unsung heroes next to the more prominent parts of the garden design.

Ultimately, a complete garden is as much about architecture as it is about plants, but there is one chief difference between its structures and the ones built by human hands. In the alfresco environment, the walls grow, the floor is alive, and the sky is the ceiling...