This species is treated as follows in the Edinburgh revision:
var. phaeochrysum R. dryophyllum Balf.f. & Forr. (type only); R. cuprescens Nitzelius – The leading characters of this, the typical variety, are: leaves not bullate above, 3 to 51⁄2 in. long, elliptic to ovate-oblong, with a brown, densely felted, sometimes agglutinated tomentum beneath. Inflorescence rachis about 1⁄2 in. long. Calyx very small. Corolla funnel-campanulate, white flushed pink, with crimson markings in the throat, up to 2 in. long. Ovary glabrous or almost so. See further on page 652.
var. levistratum (Balf.f. & Forr.) Chamberlain – Syns: all those given under the heading R. dryophyllum on page 651. This variety is what was described as typical R. dryophyllum on that page. It differs from var. phaeochrysum only in its shorter leaves and smaller flowers.
var. agglutinatum (Balf.f. & Forr.) Chamberlain R. agglutinatum Balf.f. & Forr.; R. dumulosum Balf.f. & Forr. – Like the preceding, but the indumentum agglutinated, often splitting.
The species as a whole is of wide distribution in the less rainy parts of the Sino-Himalayan region, from western Szechwan through north-west Yunnan to south Tibet. It may have been introduced by Wilson, as R. taliense, when collecting for Veitch, but most cultivated plants are from later sendings by Forrest and by Rock (although some in Sweden are from seed collected by Harry Smith in the area of Kangding (Tatsien-lu), grown as R. cuprescens).
† R. alutaceum Balf.f. & Forr. – Near to R. phaeochrysum, the main key-difference being the relatively narrower leaves, 2 to 63⁄4 in. long and 1 to 15⁄8 in. wide (length:breadth ratio 2.2-6:1 against 1.7-3(4):1 in R. phaeochrysum) (Rev. 2, p. 337). There are two varieties apart from the typical one, not clearly demarcated from each other:
var. alutaceum R. glohigerum Balf.f. & Forr.; R. roxieanum var. globigerum (Balf.f. & Forr.) Chamberlain – Indumentum woolly, pale brown.
var. russotinctum (Balf.f. & Forr.) Chamberlain R. russotinctum Balf.f. & Forr.; R. triplonaevium and R. tritifolium Balf.f. & Forr. – Indumentum rust-coloured, not woolly, the upper layer discontinuous.
var. iodes (Balf.f. & Forr.) Chamberlain R. iodes Balf.f. & Forr. – Indumentum with a brown, felted upper layer.
† R. traillianum Forr. & W.W. Sm. – This species is allied to the preceding two, though clearly distinct in having a 'powdery' indumentum composed of a single layer of short- or long-rayed rust-coloured hairs. Bot. Mag., t.8900. A native of west Yunnan and south-west Szechwan, described from a specimen collected by Forrest in the Lichiang range.
var. dictyotum (Tagg) Chamberlain R. dictyotum Tagg – This replaces var. traillianum in north-west Yunnan. The indumentum resembles that of var. traillianum, though the component hairs are slightly different (Rev. 2, p. 354).
All these species and their varieties are worthy of cultivation, if they can be obtained, with attractive, though not showy, dense trusses of white or pink-tinted, spotted flowers, borne mostly in April. They are of interest as representing a type of rhododendron that is very common in the wild.