This name is a synonym of Rhododendron mucronulatum subsp. sichotense (Pojark.) A.P. Khokhr..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12300090) with original publication details: Komarov, Fl. URSS 18: 722 1952.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:333350-1.
This name was in version 1 of The Plant List, record tro-12300090, and has not been changed.