This species is placed in the subsection Argyrophylla, but is unique in that group in having a glabrous ovary and an inflorescence with twenty to thirty flowers. In many respects it recalls R. uvariifolium in subsection Fulva and the similarity even extends to the leaf indumentum, though the hairs composing it are of a different type. The possibility of confusion between the two species is shown by the fact that Kingdon Ward's 6311 from the Tsangpo Bend area, listed as 'R. coryanum var.' in the R.H.S. Handbook, has been re-identified as R. uvariifolium (Rev. 2, p. 445). Some plants grown as R. coryanum are from this source, and the true species is rare in cultivation.
R. coryanum was described from specimens collected by Forrest on the Salween-Kiuchiang divide near the border between north-west Yunnan and south-east Tibet, and was introduced by him under F.20322 and F.20832.