An arbor usually incorporates a trellis into its structure, creating a tunnel-like passageway of climbing plants. Arbors have a continuous run of latticework from one side of the “tunnel” to the other, often in an arched shape. Arbors are a wonderful way to show off your favorite blooms, and when covered with a sheaf of roses, morning glories or other blossoms, make a visually stunning addition to your outdoor space.
An arbor can be used to create a transition between areas in a larger garden—separating a kitchen garden from a cutting garden, for example—or can be used to create a sense of drama right at the entrance of any garden.
Obelisks are tall, tapering, four-sided or spherical towers, which usually end in a pyramid shape at the top. Like arbors, their sides incorporate a trellis on which climbing plants can grow; they can also be used to suspend hanging potted plants.
An obelisk’s primary function is to draw the eye. At the center of a wheel-shaped herb garden, toward the back of a border that's overly two-dimensional, or at the end of long path, an obelisk can grab your attention and hold it. With the right “clothing,” it can be a real showstopper.