Clematis meyeniana Walp. var. insularis Sprague

Family: Ranunculaceae
English: Clematis (sp)
Japanese: ヤンバルセンニンソウ (山原仙人草) [Yanbaru Senninsō]

Viney, semi-wild masses of white flowers bloom in the late summer. I feel like this should be more common than I find it. . .

References:
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）