Rhododendron degronianum

Rhododendron degronianum is a species of rhododendron native to northern parts of Honshu, the largest island of Japan, where it grows at altitudes of about 1,800 meters (5,900 ft).

Rhododendron degronianum
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Ericaceae
Genus: Rhododendron
Species:
R. degronianum
Binomial name
Rhododendron degronianum
Synonyms

Description

Rhododendron degronianum is a shrub that grows to 2.5 metres (8 ft 2 in) in height,[1] with leaves that are narrowly to broadly elliptic, or linear lanceolate. Its flowers are funnel-shaped and pink to white.

Taxonomy

Rhododendron degronianum has three subspecies:

  • Rhododendron degronianum subsp. degronianum – leaves with fawn to reddish indumentum[2]
  • Rhododendron degronianum subsp. heptamerum [3]
  • Rhododendron degronianum subsp. yakushimanum – flowers pink fading to white, leaves with white indumentum on top, white to tan indumentum on bottom[4]
All subspecies of R. degronianum have indumentum on the underside of their leaves, here seen on a plant growing in Fukushima Prefecture, Japan

Yakushimanum hybrids

The highly variable subspecies R. degronianum subsp. yakushimanum (formerly R. yakushimanum) is found wild only on the island of Yakushima, east of Japan, whose mountainous habitat and high rainfall make it an ideal climate for rhododendrons. This subspecies has only been known outside of Japan since 1934 when seedlings were sent to England. Its popularity spread rapidly throughout the world. Many seedlings were dwarf forms measuring only 1.5 m (4.9 ft) tall and broad, but with large clusters of flowers and long narrow convex leaves, decoratively felted on the undersides. It gave rise to numerous cultivars, which are still described as R. yakushimanum (often shortened to “yaku hybrids” or “yak hybrids”) in the horticultural literature.[5] The following have achieved the Royal Horticultural Society’s Award of Garden Merit:[6]

  • R. degronianum subsp. yakushimanum[7]
  • ’Hachmann's Polaris'[8]
  • ’Hydon Dawn’[9]
  • ’Koichiro Wada’[10]

References
  1. "Rhododendron Species degronianum ssp degronianum". Hirsutum.info. Archived from the original on 2016-08-05.
  2. "More Information: Rhododendron degronianum ssp. degronianum". American Rhododendron Society.
  3. "More Information: Rhododendron degronianum ssp. heptamerum". American Rhododendron Society.
  4. "More Information: Rhododendron degronianum ssp. yakushimanum". American Rhododendron Society.
  5. Doleshi, Frank. "Rhododendron yakushimanum". Journal American Rhododendron Society. Virginia Tech. University Libraries. 25 (2). Retrieved 8 October 2018.
  6. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 85. Retrieved 7 October 2018.
  7. "RHS Plantfinder - Rhododendron yakushimanum". Retrieved 8 October 2018.
  8. "RHS Plantfinder - Rhododendron 'Hachmann's Polaris'". Retrieved 8 October 2018.
  9. "RHS Plantfinder - Rhododendron 'Hydon Dawn'". Retrieved 8 October 2018.
  10. "RHS Plantfinder - Rhododendron yakushimanum 'Koichiro Wada'". Retrieved 8 October 2018.
  • "Rhododendron degronianum", Rev. Hort. 1869: 368 1869.
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