''Rhododendron degronianum'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of rhododendron native to northern parts of

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island se ...

, the largest island of Japan, where it grows at altitudes of about .

Description

''Rhododendron degronianum'' is a shrub that grows to in height, with leaves that are narrowly to broadly

elliptic In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in ...

, or linear

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular ...

. 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 In biology, an indumentum (Latin, literally: "garment") is a covering of trichomes (fine "hairs") on a plant Davis, Peter Hadland and Heywood, Vernon Hilton (1963) ''Principles of angiosperm taxonomy'' Van Nostrandpage, Princeton, New Jersey, pa ...

* ''Rhododendron degronianum'' subsp. ''heptamerum'' * ''Rhododendron degronianum'' subsp. ''yakushimanum'' – flowers pink fading to white, leaves with white indumentum on top, white to tan indumentum on bottom Rhododendron degronianum 2

Yakushimanum hybrids

The highly variable subspecies ''R. degronianum'' subsp. ''yakushimanum'' (formerly ''R. yakushimanum'') is found wild only on the island of

Yakushima is one of the Ōsumi Islands in Kagoshima Prefecture, Japan. The island, in area, has a population of 13,178. Access to the island is by hydrofoil ferry (7 or 8 times a day from Kagoshima, depending on the season), slow car ferry (once or twic ...

, 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 tall and broad, but with large clusters of flowers and long narrow convex leaves, decoratively felted on the undersides. It gave rise to numerous

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s, which are still described as ''R. yakushimanum'' (often shortened to “yaku hybrids” or “yak hybrids”) in the horticultural literature. The following have achieved the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nor ...

’s Award of Garden Merit: *''R. degronianum'' subsp. ''yakushimanum'' *’Hachmann's Polaris' *’Hydon Dawn’ *’Koichiro Wada’

References

* "''Rhododendron degronianum''", ''Rev. Hort.'' 1869: 368 1869.

External links

The Plant List
{{Taxonbar, from=Q12067194 degronianum Endemic flora of Japan Taxa named by Élie-Abel Carrière