Juniperus occidentalis

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Juniperus occidentalis
Juniperus occidentalis 8247.jpg
At Lava Beds National Monument
Scientific classification edit
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressaceae
Genus: Juniperus
Species:
J. occidentalis
Binomial name
Juniperus occidentalis
Juniperus occidentalis range map.jpg
Natural range in dark green (light green is Juniperus grandis)

Juniperus occidentalis, known as the western juniper, is a shrub or tree native to the western United States, growing in mountains at altitudes of 800–3,000 metres (2,600–9,800 ft) and rarely down to 100 metres (330 ft).

Description[edit]

Juniperus occidentalis shoots are of moderate thickness among junipers, at 1-1.6 mm diameter. The leaves are arranged in opposite decussate pairs or whorls of three; the adult leaves are scale-like, 1–2 mm long (to 5 mm on lead shoots) and 1-1.5 mm broad. The juvenile leaves (on young seedlings only) are needle-like, 5–10 mm long; the cones are berry-like, 5–10 mm in diameter, blue-brown with a whitish waxy bloom, and contain one to three seeds; they are mature in about 18 months. The male cones are 2–4 mm long, and shed their pollen in early spring.

Taxonomy[edit]

The Sierra juniper, Juniperus grandis, is sometimes treated as a subspecies or variety of J. occidentalis (as J. occidentalis var. australis).[2][3] The two species are distinguished by range, form, as well as essential oil and genetic evidence.[4]

  • Juniperus occidentalis. Southeast Washington, eastern and central Oregon, southwest Idaho, northeastern California and extreme northwest Nevada, north of 40° 30' N latitude, east of the Cascade Range. A shrub or small tree 4–15 m tall. Exceptionally tall specimens can be found in the John Day area of Oregon well in excess of 26–28 m (85–92 ft) tall where they compete for sunlight among ponderosa pines at the bottom of some deep side canyons. Howerver, on open and barren ground 4–15 m with a bushier growth habit is more common. Cones 7–10 mm diameter. About 50% of plants are monoecious with both sexes on the same plant, 50% dioecious, producing cones of only one sex.
  • Juniperus grandis. California and westernmost Nevada, south of 40° 30' N latitude in the Sierra Nevada and San Bernardino Mountains. A medium-sized tree 12–26 m tall with a stout trunk up to 3 m diameter. Cones 5–9 mm diameter. Most plants dioecious, but about 5–10% are monoecious; the Bennett Juniper in the Stanislaus National Forest of California is considered the oldest and largest example at possibly 3000 years old, with a height of 26 m and a diameter of 3.88 m.[5]

Habitat[edit]

Juniperus occidentalis usually occurs on dry, rocky sites where there is less competition from larger species like ponderosa pine and coast Douglas-fir. In very exposed positions at high altitude, they can assume a krummholz habit, growing low to the ground even when mature with a wide trunk. Hybrids with Juniperus osteosperma are occasionally found.

Ecology[edit]

The cones are an important food for several birds, including American robin, Clark's nutcracker, phainopepla and cedar waxwing; these digest the fleshy cone scales and disperse the seeds in their droppings.

The plants often bear galls caused by the juniper tip midge, Oligotrophus betheli; these are violet-purple fading to brown, 1–2 cm diameter, with dense modified spreading scale-leaves 6–10 mm long and 2–3 mm broad at the base.

References[edit]

  1. ^ Farjon, A. (2013). "Juniperus occidentalis". The IUCN Red List of Threatened Species. IUCN. 2013: e.T42242A2965783. doi:10.2305/IUCN.UK.2013-1.RLTS.T42242A2965783.en. Retrieved 15 December 2017.
  2. ^ "Juniperus grandis R.P.Adams". Plants of the World Online. Royal Botanical Gardens Kew. Retrieved 9 July 2019.
  3. ^ Flora of North America: Juniperus occidentalis
  4. ^ Adams, R. P., S. Nguyen, J. A. Morris and A. E. Schwarzbach. 2006. Re-examination of the taxonomy of the one-seeded, serrate leaf Juniperus of southwestern United States and northern Mexico (Cupressaceae). Phytologia 88(3):299-310.
  5. ^ "Conifers.org Australis". Archived from the original on 2006-06-30. Retrieved 2006-08-05. Cite uses deprecated parameter |dead-url= (help)

Further reading[edit]