Rhododendron yakushimanum Nakai

Family: Ericaceae
English: Yakushima Rhododendron
Japanese: ヤクシマシャクナゲ (屋久島石楠花) [Yakushima Shakunagé]

Voted the world's Top Rhododendron by the RHS Rhododendron Group, these rhododendrons are Yakushima's best known flowers. Every rainy season (late May to early June) they blanket the Interior Mountains in bright pink that fades into white. There are even flower hikes arranged by the Tourism Association. Traditionally, they are revered as the embodiment of the mountain god. At elevations up to around 1500 meters, forests are dominated by var. intermedium, while the central mountains are dominated by var. yakushimanum, but I don't think plants grown by seed have been compared.

References:
Hayward, S. The Top 100 Rhododendrons for the Centenary. The Rhododendron, Camellia & Magnolia Group. Refer to: http://www.rhodogroup-rhs.org/centenary/top100/
米倉浩司・梶田忠 (2003-)　「BG Plants 和名－学名インデックス」（YList），http://ylist.info（ 2019年8月14日）
Tropicos.org. Missouri Botanical Garden. 01 Jun 2014 http://www.tropicos.org/Name/40024927