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 Carrière
Synonyms[citation needed]
Azalea degroniana (Carrière) Makino Rhododendron metternichii Siebold & Zucc.

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, south of Kyushu Island 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]

• 
  Rhododendron degronianum ssp yakushimanum -Leuven Botanical Garden, Belgium- (9227006945)
• 
  Rhododendron degronianum subsp. heptamerum var. hondoense - Hillier Gardens - Romsey, Hampshire, England
• 
  Rhododendron japonoheptamerum var hondoense2