|Tree in Yosemite National Park, California|
|Distribution of Calocedrus decurrens in the Western United States|
Calocedrus decurrens, with the common names incense cedar and California incense-cedar (syn. Libocedrus decurrens Torr.), is a species of conifer native to western North America, with the bulk of the range in the United States, from central western Oregon through most of California and the extreme west of Nevada, and also a short distance into northwest Mexico in northern Baja California. It grows at altitudes of 50–2,900 metres (160–9,510 ft). It is the most widely known species in the genus, and is often simply called 'incense cedar' without the regional qualifier.
Calocedrus decurrens is a large tree, typically reaching heights of 40–60 m (130–195 ft) and a trunk diameter of up to 3 m (9.8 ft). The largest known tree, located in Umpqua National Forest, Oregon, is 69.8 m (229 ft 0 in) tall with a 175-centimeter (69-inch) diameter trunk. It has a broad conic crown of spreading branches. The bark is orange-brown weathering grayish, smooth at first, becoming fissured and exfoliating in long strips on the lower trunk on old trees.
The foliage is produced in flattened sprays with scale-like leaves 2–15 mm (3⁄32–19⁄32 in) long; they are arranged in opposite decussate pairs, with the successive pairs closely then distantly spaced, so forming apparent whorls of four; the facial pairs are flat, with the lateral pairs folded over their bases. The leaves are bright green on both sides of the shoots with only inconspicuous stomata. The foliage, when crushed, gives off an aroma somewhat akin to shoe-polish.
The seed cones are 20–35 mm (3⁄4–1 3⁄8 in) long, pale green to yellow, with four (rarely six) scales arranged in opposite decussate pairs; the outer pair of scales each bears two winged seeds, the inner pair(s) usually being sterile and fused together in a flat plate. The cones turn orange to yellow-brown when mature about 8 months after pollination. The pollen cones are 6–8 mm (1⁄4–5⁄16 in) long.
This tree is the preferred host of a wood wasp, Syntexis libocedrii a living fossil species which lays its eggs in the smoldering wood immediately after a forest fire. The tree is also host to incense-cedar mistletoe (Phoradendron libocedri), a parasitic plant which can often be found hanging from its branches.
The incense cedar is one of the most fire and drought tolerant plants in California. Although the tree is killed by hot, stand-replacing crown fire, it spreads rapidly after lower intensity burns. This has given the incense cedar a competitive advantage over other species such as the bigcone Douglas-fir in recent years.
The wood is the primary material for wooden pencils, because it is soft and tends to sharpen easily without forming splinters.
Calocedrus decurrens is cultivated by plant nurseries as an ornamental tree, for planting in gardens and parks. It is used in traditional, xeriscapic, native plant, and wildlife gardens; and used in designed natural landscaping and habitat restoration projects in California. It is valued for its columnar form and evergreen foliage textures.
The tree is also grown in gardens and parks in cool summer climates, including the Pacific Northwest in the Northwestern United States and British Columbia, eastern Great Britain and continental Northern Europe. In these areas it can develop an especially narrow columnar crown, an unexplained consequence of the cooler climatic conditions that is rare in trees within its warm summer natural range in the California Floristic Province. Other cultivated species from the family Cupressaceae can have similar crown forms. This plant has gained the Royal Horticultural Society's Award of Garden Merit.
Incense cedar tree in McMinnville, Oregon
Incense cedar trunks in Lassen Volcanic National Park, California.
- Farjon, A. (2013). "Calocedrus decurrens". The IUCN Red List of Threatened Species. IUCN. 2013: e.T42210A2962006. doi:10.2305/IUCN.UK.2013-1.RLTS.T42210A2962006.en. Retrieved 9 November 2017.
- "Calocedrus decurrens (Torr.) Florin". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 6 January 2017 – via The Plant List.
- "Calocedrus decurrens". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 10 January 2016.
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-01-25. Retrieved 2014-10-17.
- Thieret, John W. (1993). "Calocedrus decurrens". In Flora of North America Editorial Committee. Flora of North America North of Mexico (FNA). 2. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- Powers, Robert F.; Oliver, William W. (1990). "Libocedrus decurrens". In Burns, Russell M.; Honkala, Barbara H. Conifers. Silvics of North America. Washington, D.C.: United States Forest Service (USFS), United States Department of Agriculture (USDA). 1 – via Southern Research Station (www.srs.fs.fed.us).
- Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4
- Earle, Christopher J., ed. (2018). "Calocedrus decurrens". The Gymnosperm Database.
- Hawksworth, Frank G.; Wiens, Delbert (1993). "Phoradendron libocedri". In Hickman, James C. The Jepson Manual: Higher Plants of California. University and Jepson Herbaria.
- Franklin, Janet; Spears-Lebrun, Linnea A.; Deutschman, Douglas H.; Marsden, Kim. 2006. Impact of a high-intensity fire on mixed evergreen and mixed conifer forests in the Peninsular Ranges of southern California, USA. Forest Ecology and Management. 235(1-3): 18-29. 
- University of Michigan—Dearborn: Native American Ethnobotany of Calocedrus decurrens[permanent dead link]
- Chesnut, Victor King (1902). Plants used by the Indians of Mendocino County, California. Government Printing Office. p. 404. Retrieved 24 August 2012.
- Mitchell, A. F. (1996). Alan Mitchell's Trees of Britain. Collins ISBN 0-00-219972-6.
- RHS Plant Selector Calocedrus decurrens AGM / RHS Gardening
|Wikimedia Commons has media related to Calocedrus decurrens.|