Early arbors were made by bending the trunks of young or small trees to form a living, shady area of rest. Modern arbors are constructed of a various materials but still provide the same basic service. Arbors have taken on other uses over the years. Once associated with cottage gardens, arbors now find acceptance in many landscapes.
Princeton University defines an arbor as a framework that supports climbing plants. In its most basic form, the definition fits. Some are used to create an entryway complete with a swinging gate. Others are the focal point of a landscaped botanical garden. Arbors can function as supports for grapevines, making them functional as well as decorative.
Frequently arbors are seen as tall arched sentinels separating outdoor spaces such as the street or yard from the garden. Traditional arbors are constructed of two upright walls and a flat roof that connects the walls. Tunnel arbors are created by aligning multiple arbors, one behind the other. When covered in vines, the effect is that of passing through a tunnel of vines or flowers. Some have a cross-hatched design of vertical and horizontal supports, while others can be made of metal wrought in elaborate patterns and swirls.
Arbors do not come in "standard" sizes, though universally they are tall enough and span an area wide enough for a person to comfortably walk beneath. When being used as an entry point from one area to another, this is sufficient. In the case of creating a shady area of rest, the arbor might be large enough to span a bench for seating. Tunnel arbors are more of a custom design and are fitted to the space they occupy.
Arbors are made from most of the typical materials used in gardens. Wood, plastic, metal and wicker all have their places. Wicker is mostly a decorative focal point in a garden and does not hold up well to heavy-growing vines. Metal such as wrought iron adds a heavy presence to the landscape and withstands strong winds. Bear in mind, it will oxidize over time. Plastic arbors are lightweight and easy to install. Extreme or prolonged periods of hot or cold can cause plastic to become brittle and crack. Wood arbors have a more natural look, but unless specially treated, can succumb to weather and insects.
Arbors need to be installed carefully and well anchored. High winds or impact from lawn mowers or vehicles can cause them to topple. Because the weight of the plants as they grow can tug the arbor in one direction, the arbor can become unstable and dangerous. Weather and insect damage can also cause the arbor to decay. Covered by plant matter, the damage can be difficult to detect.