Red rhododendron - Red rhododendron

...Akebono azaleas have five leaves that grow in whorls at the end of the branches, and the corolla is broad bell-shaped and opens wide. Akebono azalea R. pentaphyllum Maxim. is found in the mountains on the Pacific side of Honshu from the Kii Peninsula westward, Shikoku, and Kyushu, and its variant, Akayashio, is found on the Pacific side of the Chubu region to southern Tohoku. Compared to the above species, Renge azaleas have leaves that grow scattered on the branches, and the lower part of the corolla is thin and tubular, with only the upper part opening wide. ...

*Some of the terminology that mentions "Akayashio" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…アケボノツツジ類は5枚の葉が枝先に輪生し，花冠は広鐘形で広く開く。本州の紀伊半島以西，四国，九州の太平洋側の山地に分布するアケボノツツジR.pentaphyllum Maxim.と，その変種であるアカヤシオが中部地方から東北地方南部の太平洋側に分布する。レンゲツツジ類は葉は上記の種類と比較すると散らばって枝につき，花冠の下部は細い筒形で上部のみが広く開く特徴をもつ。…

※「アカヤシオ」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報