Incense cedar is a coniferous tree of the genus Calocedrus. There are three species, though one, Calocedrus decurrens or the California incense cedar, is sometimes classified as belonging to the genus Libocedrus. C. decurrens is native to western North America, with a range covering parts of Oregon, California, Nevada, and Baja California in northwest Mexico. The other two species are native to parts of Asia; Calocedrus formosana, or Taiwan incense cedar, grows only in Taiwan, while Calocedrus macrolepis, or Chinese incense cedar, grows in parts of China, Laos, Myanmar, Thailand, and Vietnam.
C. decurrens is the most widely known incense cedar species. The trees typically grow 130 to 200 feet (40 to 60 meters) high, with a trunk of 10 feet (3 meters) in circumference. C. decurrens is cultivated as an ornamental tree, popular for its hardiness in times of drought. It is grown in Britain, parts of northern Europe, and parts of the United States outside of its native range. The wood of C. decurrens is used in most pencils, since it is soft and tends not to splinter.
C. decurrens serves as the host of the incense cedar wasp or wood wasp, Syntexis libocedrii. The wood wasp is considered a living fossil, since its family has an extensive prehistoric fossil record, though it is the only remaining species in its genus. The inset lays its eggs only in recently burnt trees, often while they are still smoldering. C. decurrens is also the host to incense cedar mistletoe, Phoradendron libocedri, a parasitic flowering shrub with small pink or yellow berries.
C. formosana reaches heights of 65 to 80 feet (20 to 20 meters). It grows only in Taiwan, over an area less than 1,930.5 square miles (5,000 square km), and is classified as an endangered species. The tree is threatened by over harvesting and habitat loss. It is sometimes considered a variety of C. macrolepis, rather than a separate species.
C. macrolepis is similar in size and appearance to C. formosana, the main difference between the two being the size of the cone stem. C. macrolepis has a cone stem of about 0.2 inches (5 millimeters) long, while the cone stem of C. formosana is 2 to 3 times longer. While C. macrolepis is also threatened by over harvesting, its conservation status is slightly better than that of C. formosana. It is often planted in its native range in addition to being harvested in the wild.