Gimme shelter

Pergolas are classic garden structures. They're easygoing, open-air architectural elements that bring the comforting embrace of an interior room into the garden, and define and distinguish an outdoor space. A pergola is an irresistible destination, an unfailingly nice, lightly shaded place to sit and take the air.

James Van Sweden, a landscape architect and designer whose naturalistic work captures much of modern American garden style, calls arbors, pergolas, trellises and garden pavilions the "icing on the cake after the hard work of planning, building and planting a garden." A well-made and properly proportioned pergola adds "drama in the midst of repose," he says.

Katherine Brooks, a garden designer in Richmond, Va., added a pretty pergola to the front of her home, instantly setting the vintage ranch house apart. The structure extends all the way across the front of the house, over a new porch where there had been none. Instead of a brooding brow of a roofline, the pergola's open architecture is graciously welcoming. It shades the new porch lightly, frames the bright pink front door and reveals something of the outgoing spirit of the enthusiastic gardener who lives within.

A gardener in Williamsburg, Va., recently worked with garden designer Joe Hertzler on a freestanding pergola to provide an inviting destination in the backyard. Flowering vines clamber up the posts, and the only furnishing is a porch swing, heaped with cushions, hung from stout beams under the peaked roof. Eventually, the vines will provide dappled shade under the structure, but until they do, the crosspieces of the pergola cast graphic shadows on the grass. It's as pretty from across the yard as it is when you're sitting under it.

Whether a pergola is attached to a house or set out in the more open context of the garden, its style and construction should suit the architecture of the home and should be in scale with its surroundings, says Bob Schaffer, owner of Nantucket Trellises in Downers Grove, Ill. Plan ahead, he says, "and think about where you like to entertain, where does the sun come up and go down." If the pergola will cover a patio, the patio has to be big enough to support it gracefully. Schaffer prefers for the posts of the pergola to rest on the patio, not outside it, so the pergola and patio look like one unified concept.

Scale is important, especially if you have in mind the pergola will shelter a dining table and chairs. "The whole outdoor furniture industry thinks big, and before you know it, your space will be filled," Schaffer says. If you favor outdoor sofas, lounge chairs and conversational seating, rather than cute bistro sets, it might be a good idea to shop for the furniture before you define the dimensions of your patio and pergola.

Schaffer likes to position the beams (or purlins, as the crosspieces are called), to cast interesting shadows as the sunlight moves across the garden. If you need more shade, a length of shade cloth (available from garden shops) stretched over the pergola will soften the light without turning the shelter into a dark closet. Annual or perennial vines (roses come to mind, of course, but morning glories, gourds and striking purple hyacinth beans are all good choices) will also cover a pergola and create dappled light.

Graceful proportions are critical, Schaffer says. A comfortable height for the header that supports the purlins is 7 to 8 feet, he says. Plans and designs for weekend gardeners usually show pergolas with an 8-foot clearance under the purlins. Internet resources for do-it-yourself pergola projects show plans with purlins spaced between 6 and 12 inches apart; you'll want to test this on your own structure to decide what looks best in your setting.

Before you get started, check local codes to make sure the structure you're adding complies with building and setback requirements. Professional builders will know whether a permit or variances are required, but if you're taking on the project yourself, it's best to check with permit departments while you're still in the planning stage.

Pergolas shape the experience of a garden, frame views in interesting new ways and create intimate spaces. It's a pretty neat trick for structures that don't really enclose anything: they just open up new possibilities.

Sources

• Nantucket Trellises, nantuckettrellises.com
• Katherine Brooks, landscape designer, katherinebrookslandscapes.com.
• James Van Sweden, Oehme van Sweden Landscape Architects, ovsla.com.
• Joe Hertzler, Hertzler & George landscape design, hertzlerandgeorge.com

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Ross is a garden writer in Kansas City, Mo.