As you sketch out plans for your landscape, the first few of drafts look like blobs on a page as you consider where to put what and the proportion of one space to another. Each blob or bubble represents a space—turf, border, bed, pool, patio, tree and so on—and may change size and shape as you prioritize your needs and wants. Eventually, the blobs become more defined and merge into one another; a bubble diagram morphs into a concept plan.

Determine the shape of larger spaces such as lawns and courtyards first, which sets the tone for the rest of the landscape's bedlines. "Using a similar form throughout the design helps create unity and structure within the design," according to the Iowa State University Extension.

The architecture of your house may inform the choice of form composition, but it is largely a matter of personal taste. Do you prefer curves or angles? Circles or rectangles? Symmetrical or asymmetrical? Formal or informal?

"Most homeowners prefer curvilinear because it's less formal than rectilinear," says Pete Marsh, a landscape designer with Buck & Sons in Columbus, Ohio. There's also the perception that curves are relaxing and more natural.

But they can also be cliche. "Geometry can be a beautiful thing," says Garry Menendez, a landscape architect and associate professor of plant sciences at the University of Tennessee. He adds: "We too often feel compelled to force a curve into an area in which it makes very little sense. Be creative, bold and daring. Try a straight line now and then."

For example, it's possible to soften symmetrical, straight-lined beds and borders with plants arranged in flowing drifts or to inject a note of formality into a free-flowing landscape with a raised herb garden arranged in a geometric pattern. The key is to adhere to the design principles of scale, balance, mass and harmony.