Japanese pergolas are outside structures built to mark the transition from one structure, garden or lawn area to another, to provide support for climbing plants or to cast shade over a walkway. Japanese pergola brings a sacredness and dignity to any garden, whether it be western or Asian-styled. There are several Japanese pergola designs. And the most common materials that used in Japanese pergola designs are wood, metal or plastic. Wood is the most popular material choice, and an important consideration is the type of wood chosen. Redwoods, such as cedar, are good choices because they are naturally resistant to insect infestations, rot and decay. They do not need chemical treatment. This consideration becomes important if the Japanese pergola is to support climbing plants. Treated woods contain poisonous chemicals which can harm or kill plants.