Named for the spicy aroma of the wood, incense cedars are interesting trees. Close relatives of the northern white cedars (Thuja spp.); incense cedars are relatively rare in the natural world, although they were formerly common. Considered at one time to be represented a single species, botanists now recognize several different species of incense cedars. The only North American native, California incense cedars (Calocedrus decurrens) range from California to northern Oregon, while C. formosana, C. macrolepis and C. rupestris grow in Taiwan, China and Vietnam, respectively. Additionally, paleobotanists have described an extinct species – C. huashanensis – that formerly grew in China.
Size and Shape
Incense cedars are long-lived trees that often reach ages in excess of 500 years. Other forest species often outcompete these trees, and retard their growth rate. However, over the course of their long lives, incense cedars often reach moderately large sizes. Typical specimens grow to between 60 and 80 feet, although some giants of the Sierra Nevada Mountains grow twice as tall.
Because they are drought resistant, relatively pest free natives of California, they can make a wonderful addition to your property. Their form and foliage make them aesthetically pleasing, while their extremely dense foliage makes them excellent for windscreens. These trees help support wildlife as the tiny seeds that emerge from the 1-inch-long cones feed a variety of songbirds and native rodents.
Can’t Stand the Heat?
Incense cedars are well adapted for hot, parched conditions; once established, they are remarkably drought tolerant. According to U.S. Forest Service, incense cedars tolerate dry conditions better than sugar pine, Douglas firs and grand firs, although ponderosa pines are better equipped to deal with drought in sandy areas than the cedars. (Oliver) While they often become canopy trees on southern or southwestern hillsides, other species outcompete incense cedars on moist sites, causing them to remain much smaller. Although high-intensity crown fires kill incense cedars, they often survive low-intensity ground fires.
Variation and Variety
Incense cedars vary slightly based on their location. Southern California specimens reach shorter heights than their northern relatives do. Additionally, these southern individuals often have shorter branches, and they tend to exhibit a more columnar growth form. Perhaps unsurprisingly, these southern varieties are more susceptible to frost damage than their northern counterparts are.
Commercial Uses
Incense cedars make wonderful ornamental trees, even well-outside their native range. They are popular in Europe and along the Atlantic seaboard of the United States. Incense cedars require partial to full sun, well-drained soils and protection from strong winds. Because they grow quite large, they are best planted on large properties where they have ample room. Fortunately, for those who share space with deer, the hoofed browsers rarely feed on incense cedars.
Because the wood of incense cedars resists decay — even in the presence of moisture — it is often used in outdoor construction. The wood also accepts paint well, leading many to use it for building picnic tables, exterior siding and fence posts. However, one of the most common uses of incense cedar is in the manufacture of pencils.
Threats
Good ‘ol root rot brings more incense cedars to their knees than any other cause, although pocket dry rot (Tyromyces amarus) is also a threat to these gorgeous conifers. This fungus causes significant internal decay, which ultimately compromises the tree’s structural integrity. Healthy bark provides an effective barrier against fungal colonization, but knots and damaged areas are vulnerable. Pocket dry rot primarily affects those trees that grow on favorable sites; for example, some stands in the Sierra Nevadas exhibit 100 percent colonization of the mature specimens.
Incense cedars may also serve as the host for incense-cedar mistletoe (Phoradendron juniperinum libocedri), but the parasitic epiphyte rarely causes tree death. A number of insects feed on these trees, but few cause serious problems. The only common foliage disease – Gymnosporangium libocedri – rarely causes the trees to die.
References
Oliver, R. F. (n.d.). Incense-Cedar. U.S. Forest Service.