Western, Sierra or yellow juniper; yellow or western red cedar (Peattie 1950).
There are two subspecies:
Other authors have treated the australis (Sierra juniper) populations as a variety (Holmgren and Holmgren 1972) or, more recently, have elevated it to the status of a species (Adams et al. 2006). Farjon (2005) favors varietal rank, citing "weakly expressed morphological differences" between the taxa. Conversely, Adams et al. (2006) argue that not only are the morphological differences consistent, but that the molecular differences that he has investigated are significant as well. His analysis indicates that the two taxa of J. occidentalis share a clade with J. osteosperma, but that australis is sister to an occidentalis-osteosperma clade, and that this warrants elevating australis to species rank. In this connection it is worth noting that both occidentalis and australis have been reported to hybridize with J. osteosperma in northwestern Nevada (Miller et al. 2005, Adams 1993).
I find that I must differ from Farjon (2005) in that I have found the morphological differences between the two taxa to be consistent, and moreover there are very clear ecological differences, so that the species has a bimodal niche subdivided along taxonomic lines, wherein the Sierra juniper is a tree of mesic high mountains and the western juniper is one of semi-arid montane areas, with very few intermediates. This strong and bimodal difference between the taxa supports a subspecies ranking. Conversely, I believe that Adams et al. (2006) have placed too much faith in the power of their molecular analysis, which has examined only nrDNA and trnC-trnD sequences. Other work in the Cupressaceae has found that the body of taxonomic evidence may shift significantly as new and different molecular markers are taken into consideration (see the discussions of Cupressaceae and Cupressus), and in this case, further work may well show that J. occidentalis is not paraphyletic. On balance I feel that a subspecies ranking is most appropriate for these taxa.
Synonymy for the species (Farjon 2005):
Monoecious or dioecious evergreen trees 10-15(-30) m tall and 30-100(-250) cm dbh, usually single-stemmed. Branches thick, ascending or spreading, often curved or contorted, the foliage branches forming dense rounded tufts at the ends of the heavy main branches, forming a pyramidal crown in young trees, becoming rounded and irregular in old trees. Bark first smooth, pink-brown, then becoming grey and flaking; then fibrous, red-brown to brown, exfoliating in thin strips. Branchlets numerous, stout, 3-4-sided in cross section, (1.2-)1.5-2 mm thick, branching at 60° or less. Leaves dark green, abaxial glands oval, conspicuous, often with yellow or white exudate, margins denticulate (at 20×); whip leaves 3-6 mm, not glaucous adaxially; scale-like leaves in alternate whorls of 3, 2-3 × 2 mm, ovoid-rhombic, acute or obtuse, not overlapping, appressed. Pollen cones numerous, terminal on short ultimate branchlets, subglobose to ovoid-oblong, 3-5 × 2-3 mm, yellow-green maturing yellow-brown; microsporophylls (10-)12-16(-18). Seed cones maturing in 2 years, terminal on ultimate branchlets, initially 2 mm diameter with 4-6 spreading bracts, growing in two seasons from purple-red to blue or purple with a glaucous bloom, subglobose to ellipsoid, (6-)7-9(-10) × (5-)6-8 mm, fleshy or pulpy, more or less resinous, eventually dry, falling soon after ripe. Seeds 1-2 per cone, ovoid or semi-ovoid, 5-6(-7) × 4-5 mm, with shallow grooves and resinous pits, yellowish-brown. Cotyledons 2-3(-4), juvenile leaves only on seedlings, in whorls of 3 (Adams 1993, Farjon 2005).
Subsp. occidentalis is often (50%) monoecious. Branchlets mostly have 3 scale leaves per whorl. Mature seed cones average 7.5 mm diameter. Seedlings mostly have 2 cotyledons (Adams 1993, Farjon 2005).
Subsp. australis is primarily (90%) dioecious. Branchlets mostly have 4 scale leaves per whorl. Mature seed cones average 8.5 mm diameter. Seedlings often have 3-4 cotyledons (Adams 1993, Farjon 2005).
USA: Washington, Oregon, Idaho, Nevada and California (subsp. australis only in California and extreme W Nevada). See also Thompson et al. (1999). Occurs at elevations of 185-3050 m (Dealy 1990). Hardy to Zone 5 (cold hardiness limit between -28.8°C and -23.3°C) (Bannister and Neuner 2001, subspecies not specified).
Both subspecies have been used in climate studies.
See the subspecies descriptions.
See the subspecies descriptions.
This species is a host for the mistletoe Phoradendron juniperinum Engelm. ex A. Gray, shown in photos at left.
Dealy, J.E. 1990. Western juniper, in Burns and Honkala (1990).
Holmgren, A. H. and N. H. Holmgren. 1972. Intermountain Flora 1: 239.
Hooker, William Jackson. 1838. Flora Boreali-Americana 2 (10): 166.
Miller, R.F., J.D. Bates, T.J. Svejcar, F.B. Pierson, and L.E. Eddleman. 2005. Biology, Ecology, and Management of Western Juniper (Juniperus occidentalis). Oregon State University Agricultural Experiment Station Technical Bulletin 152. 82pp. (Highly recommended. Can be found on the Web.)
Last Modified 2012-11-28