Within the Rhododendron fastigiatum article...

R impeditum Balf. f.

R. fastigiatum of the 1st edition of this work, not Franch.
R. semanteum Balf. f., nom. inedit

This species was discovered by Forrest on the eastern and western flanks of the Lichiang range, Yunnan, in 1910, and was introduced by him in that year. It was at first considered to be R. fastigiatum, and went into cultivation under that name, but was described as a new species in 1916. Balfour wrote: ‘Like that plant [R. fastigiatum] in its cushion habit its foliage is very different, and one can distinguish the two plants at a glance. Rh. fastigiatum has a grey hoary appearance, Rh. impeditum dark green. Both the plants have discontiguous under-leaf scales, but whilst in Rh. fastigiatum the bare intervals of epidermis are greyish, often tinted slightly red, in Rh. impeditum the epidermis is mat green.’ This difference in leaf-colouring is especially noticeable in the young growths, and there is the further difference that in R. fastigiatum the scales on the blade beneath, seen under low magnification, are opaque, waxy and very solid in appearance, whilst those of R. impeditum are light brown and lustrous. But on year-old leaves of R. fastigiatum a few of the scales have lost their wax, and even on younger leaves the scales on the midrib beneath are like those of R. impeditum. Other distinctions are that the flowers are usually not more than three per truss and are mauve rather than purple. But the key-character relied on by Balfour – outside of corolla scaly in R. fastigiatum, not so in R. impeditum – does not hold good. There is no constant difference in size or shape of leaf.R. impeditum is not common in commerce, but is available from specialist nurseries (this, of course, applies to the true species, not to R. fastigiatum masquerading as R. impeditum). It received an Award of Merit in 1944 when shown by the Sunningdale Nurseries, who raised it from Rock 59263, collected in the type-area. Earlier, the same award had been given to a plant from seed of F.20492, collected in the Muli area of S.W. Szechwan and distributed under the unpublished name R. semanteum. No example of this form has been seen, but the name R. semanteum is given as a synonym of R. impeditum by Hutchinson in Species of Rhododendron.


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