Wooden arbors provide instant shade with slats typically running along the open roof. They create thresholds and garden room enclosure. They add romance to your design.
Arbors and other outdoor structural elements need to be appropriately scaled. When in doubt about the scale needed for your landscape design, make a mock-up of the components of your structural design out of cardboard, and test it outdoors. This is a simple hack, and can save you embarrassment later. There is nothing sillier-looking than a spindly arbor or pergola.
Wooden posts must be at least four by four, preferably six by six. Pickets and crossbars need to be substantial, too. Besides holding up heavy plants like Wisteria vines, the thick, visual weight of appropriately-sized structures suits outside proportions.
Arbor posts need to be as sturdy as fence posts. Their footings should be treated the same, incorporating methods for water to drain away from the wood and to separate contact with wet soil, to prevent rotting. Arbors should be difficult to climb, since they are not meant to hold the weight of people. Posts can provide clever methods to run electrical wiring to special lighting fixtures.
Carriage bolts are the standard joining hardware for wooden arbors and decks. Beams can be added to the posts to run slats along the arbor top. Trellises and seating can be easily incorporated into the structure using the same posts. When an arbor is larger than a threshold, it can be used as a square, open-roofed, outdoor room or covered walkway. Then it is called a pergola.