This name is a synonym of Rhododendron mucronulatum Turcz..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50054217) with original publication details: Mém. Acad. Imp. Sci. Saint Pétersbourg, Sér. 7 16(9): 44 1870.
This name was in version 1 of The Plant List, record tro-50054217, and has not been changed.