Rhododendron occidentale
Encyclopedia
Rhododendron occidentale, the Western Azalea, is one of two deciduous
Rhododendron
species native to western North America
(the other is Rhododendron albiflorum). The Western Azalea is known to occur as far north as Bandon
, Oregon
. It is found as far south as the Palomar Mountain
area in southern California
. Typically found in the coastal ranges of western North America, it also grows in the Cascade and Sierra Nevada mountain ranges, but is not known east of them.
growing to 5 m tall. The leaves
are deciduous
, 3-9 cm long and 1-3 cm broad. The flower
s are 3.5-5 cm diameter, with five lobes on the corolla; color varies from white to pink, often with a yellow blotch.
There is considerable diversity in the form and appearance of this species, with genetic diversity seeming to reach its highest level along the coast in the vicinity of the border between Oregon and California. It is tolerant of serpentine soils to the point that serpentine soils (along with surface water) can be used as a sign of its presence in southern Oregon. For this reason, it is a part of the unique plant community found in the serpentine barrens of the Siskiyou Mountains
, along with Darlingtonia californica
and Cypripedium californicum
. It is usually found in wetlands although, like other rhododendrons, it does not grow with its roots submerged in water. It prefers both more moisture and more sunlight than Rhododendron macrophyllum
, an evergreen rhododendron with a similar range.
.
The Western Azalea was an early contributor in the development of deciduous hybrid azalea
s in Great Britain, such as the Exbury
azaleas.
During the twentieth century it has been the subject of ongoing plant exploration as at least three generations of rhododendron enthusiasts have sought out unusual forms for use in the garden and to record for science. Many of those forms are now conserved in the Smith-Mossman Western Azalea Garden at Lake Wilderness Arboretum
in Maple Valley
, Washington state, USA.
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
Rhododendron
Rhododendron
Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...
species native to western North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
(the other is Rhododendron albiflorum). The Western Azalea is known to occur as far north as Bandon
Bandon, Oregon
- Economy :Like many communities on the Oregon coast, Bandon had significant fishing and timber industries, which were greatly diminished by the 1980s, though some remnants still exist. Bandon's current economy revolves around wood products, fishing, tourism, and agriculture...
, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
. It is found as far south as the Palomar Mountain
Palomar Mountain
Palomar Mountain is a mountain in the Peninsular Ranges in northern San Diego County. It is famous as the location of the Palomar Observatory and Hale Telescope, and known for the Palomar Mountain State Park.-History:...
area in southern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. Typically found in the coastal ranges of western North America, it also grows in the Cascade and Sierra Nevada mountain ranges, but is not known east of them.
Description
Rhododendron occidentale is a shrubShrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
growing to 5 m tall. The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
, 3-9 cm long and 1-3 cm broad. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are 3.5-5 cm diameter, with five lobes on the corolla; color varies from white to pink, often with a yellow blotch.
There is considerable diversity in the form and appearance of this species, with genetic diversity seeming to reach its highest level along the coast in the vicinity of the border between Oregon and California. It is tolerant of serpentine soils to the point that serpentine soils (along with surface water) can be used as a sign of its presence in southern Oregon. For this reason, it is a part of the unique plant community found in the serpentine barrens of the Siskiyou Mountains
Siskiyou Mountains
The Siskiyou Mountains are a coastal mountain range in the northern Klamath Mountains in northwestern California and southwestern Oregon in the United States. They extend in an arc for approximately from east of Crescent City, California northeast along the north side of the Klamath River into...
, along with Darlingtonia californica
Darlingtonia californica
Darlingtonia californica , also called the California Pitcher plant, Cobra Lily, or Cobra Plant, is a carnivorous plant, the sole member of the genus Darlingtonia in the family Sarraceniaceae. It is native to Northern California and Oregon, growing in bogs and seeps with cold running water...
and Cypripedium californicum
Cypripedium californicum
The California Lady's Slipper is a member of the orchid genus Cypripedium, the Lady's Slipper orchids. It is native to the western United States, where it has a very restricted range and can only be found in the mountains of southwestern Oregon , and northern California...
. It is usually found in wetlands although, like other rhododendrons, it does not grow with its roots submerged in water. It prefers both more moisture and more sunlight than Rhododendron macrophyllum
Rhododendron macrophyllum
Rhododendron macrophyllum, the Pacific Rhododendron, Coast Rhododendron or Big Leaf Rhododendron, is a broadleaf evergreen rhododendron species native to western North America.-Distribution:...
, an evergreen rhododendron with a similar range.
History and cultivation
The Rhododendron occidentale plant was described by explorers in western North America in the nineteenth century. At one time, the various geographic races were each classified as separate species. Seed was sent to Veitch Nursery in England in 1850 by William LobbWilliam Lobb
William Lobb was a Cornish plant collector, employed by Veitch Nurseries of Exeter, who was responsible for the commercial introduction to England of Araucaria araucana from Chile and the massive Sequoiadendron giganteum from North America.He and his brother, Thomas Lobb, were the first...
.
The Western Azalea was an early contributor in the development of deciduous hybrid azalea
Azalea
Azaleas are flowering shrubs comprising two of the eight subgenera of the genus Rhododendron, Pentanthera and Tsutsuji . Azaleas bloom in spring, their flowers often lasting several weeks...
s in Great Britain, such as the Exbury
Exbury Gardens
Exbury Gardens is a famous garden in Hampshire, England, which belongs to a branch of the Rothschild family. It is situated in the village of Exbury, just to the east of Beaulieu across the river from Bucklers Hard...
azaleas.
During the twentieth century it has been the subject of ongoing plant exploration as at least three generations of rhododendron enthusiasts have sought out unusual forms for use in the garden and to record for science. Many of those forms are now conserved in the Smith-Mossman Western Azalea Garden at Lake Wilderness Arboretum
Lake Wilderness Arboretum
Lake Wilderness Arboretum , known for a time as the South King County Arboretum, is an arboretum located in Maple Valley, Washington. It is open daily without charge...
in Maple Valley
Maple Valley, Washington
Maple Valley is a city in King County, Washington, United States. The population was 22,684 at the 2010 census.-History:The area was first settled in 1879 by three men who were improving a trail and brought their families in. When a name for a future community was proposed, the names Vine Maple...
, Washington state, USA.
External links
- Jepson Flora Project: Rhododendron occidentale
- Western Azalea Garden: Rhododendron occidentale photos - Maple Valley, WashingtonMaple Valley, WashingtonMaple Valley is a city in King County, Washington, United States. The population was 22,684 at the 2010 census.-History:The area was first settled in 1879 by three men who were improving a trail and brought their families in. When a name for a future community was proposed, the names Vine Maple...