California Incense-Cedar

Appearance

"Calocedrus decurrens" is a large tree, typically reaching heights of 30–40 meters and a trunk diameter up to 1.2 m. The largest known tree, located in Klamath National Forest, Siskiyou County, California, is 47.98 m tall with a 12 m circumference trunk and a 17.5 m spread. Specimens form 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. Specimens can live to over 500 years old.

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 foliage, when crushed, gives off an aroma somewhat akin to shoe-polish.

The seed cones are 20–35 mm long, pale green to yellow, with four scales arranged in opposite decussate pairs; the outer pair of scales each bears two winged seeds, the inner pair 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.

Distribution

The bulk of the tree's range is in the United States, from central-southwestern Oregon through most of California and the extreme west of Nevada, as well as a short distance into northwest Mexico in northern Baja California.

Habitat

At lower elevations, associated trees include oaks and ponderosa pine. Giant sequoia bears similarities to the species, but has sharp leaves. In the south–southwest U.S. some have confused bushy junipers for incense cedar.

With its thick basal bark, 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. Incense cedar is more shade tolerant than Douglas-fir, but not as much so as grand or white fir. It grows slowly when needed to outlast competition.

This tree is the preferred host of a wood wasp, "Syntexis libocedrii" a species which lays its eggs in the smoldering wood immediately after a forest fire. The tree is also host to incense-cedar mistletoe, a parasitic plant which can often be found hanging from its branches. Fire scars provide an entry point for "Tyromyces amarus". "Gymnosporangium" rust disease afflicts the trees, but is rarely fatal.

For numerous birds during the wintertime, "Calocedrus decurrens" has been seen to be used for foraging. According to the United States Department of Agriculture, in areas of the Western Sierra Nevada in California, numerous species of birds are thought to use the incense cedar as a "foraging substrate" so that they can attain as much food as needed. Human impacts on these trees due to forest management practices have caused issues for many of these birds, threatening the use of the incense cedar as a forage substrate.

Uses

The wood is soft and light, and has a pleasant odor and is generally resistant to rot. It has been used for external house siding, interior paneling, and to make moth-resistant hope chests. It was once the primary material for wooden pencils, because it is soft and tends to sharpen easily without forming splinters.