Everything about Juniperus Occidentalis totally explained
Juniperus occidentalis (
Western Juniper and
Sierra Juniper) is a
shrub or
tree native to the western
United States, growing in
mountains at altitudes of 800-3,000 m (rarely down to 100 m).
The shoots are of moderate thickness among
junipers, 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're mature in about 18 months. The male cones are 2-4 mm long, and shed their pollen in early spring.
It usually occurs on dry, rocky sites where there's less competition from larger species like
Ponderosa Pine and
Coast Douglas-fir.
Hybrids with
Juniperus osteosperma are occasionally found.
The cones are an important food for several
birds, including
American Robin,
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 (
Bibionomorpha: Cecidomyiidae); 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.
There are two
varieties, treated as
subspecies by some botanists:
- Juniperus occidentalis var. occidentalis Western Juniper. 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. Exceptinally tall specimens can be found in the John Day area of Oregon well in excess of 26-28 m tall (80-90 feet+) competing for sunlight among Ponderosa Pines at the bottom of some deep side canyons, but 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 occidentalis var. australis Sierra Juniper. 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 one of the oldest and largest examples at possibly 3000 years old, with a height of 26 m and a diameter of 3.88 m
(External Link
).
References and external links
Adams, R. P. (2004). Junipers of the World: The genus Juniperus. Trafford Publishing ISBN 1-4120-4250-X
Gymnosperm Database: Juniperus occidentalis
Gymnosperm Database: Juniperus occidentalis var. australis
Flora of North America: Juniperus occidentalis
Further Information
Get more info on 'Juniperus Occidentalis'.
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