Rhododendron brachycarpum var. brachycarpum is an evergreen shrub, sometimes resembling a small tree in habit but only about 1-4m high. Its natural range covers central and northern Japan, including the Russian-administered island of Kunashiri. The robust and large-leafed form growing in Korea is sometimes considered a subspecies, sometimes a race, and is known in Finland as Mustila Rhododendron.
Because they are geographically isolated from each other, the various populations of this rhododendron show large variations. Those growing in Japan are usually smaller than those on the continent, and especially in full light are dense shrubs. The shiny leaves are smaller, 10-15 cm long, with thin reddish hairs on the undersides. The smallish white (sometimes with red) flowers are among the latest rhododendrons to open at Mustila, usually not till after mid-June.
As a mountain species, this rhododendron is adapted to cool summers and is hardy in cold winters. Because it begins growing early, the new growth is often damaged in places susceptible to spring frosts. Its multiplicity of habit can be observed at Mustila, where shrubs vary from low ground-cover to almost tree-like forms.
In Western literature, several subspecies are recognized, e.g. subsp. fauriei, whose leaf undersides are hairless. This form does not grow at Mustila, though several plants have been received under the Rhododendron fauriei name. This is due to the Asian naming system, in which Rhododendron brachycarpum and Rhododendron fauriei are synonyms and Rhododendron fauriei has priority, regardless of any – or no - hairiness.