Calocedrus decurrens (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 50–2900 m. It is the most widely-known species in the genus, and is often simply called Incense-cedar without the regional qualifier.
It is a large tree, typically reaching heights of 40-60 m and a trunk diameter of up to 3 m (maxima, 69 m tall and 4.5 m diameter), and with 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 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 seed cones are 20–35 mm 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 long.
It is also a popular ornamental tree, valued for its drought tolerance. It is also grown particularly in cool summer climates (notably eastern Britain and elsewhere in northern Europe, and in parts of the northern Pacific Northwest of North America) for its very narrow columnar crown. This narrow crown is not restricted to selected cultivars but is an unexplained consequence of the climatic conditions in these areas, and is not shown by trees in the wild; many other species in the Cupressaceae show similar effects to a smaller degree.