An evergreen shrub or small tree in the wild. Leaves elliptic or oblong-elliptic, rounded and mucronate at the apex, rounded to broad-cuneate at the base, 11⁄4 to 3 in. long, 13⁄8 to 17⁄8 in. wide, dull green and sparsely scaly above, densely scaly and glaucous green beneath; stalk about 1⁄2 in. long. Flowers opening in May, in terminal trusses of five to ten; pedicels up to 7⁄8 in. long. Calyx small, shortly lobed, densely scaly. Corolla creamy yellow or soft yellow, unspotted, tubular-campanulate, 1 to 11⁄2 in. long, with five slightly spreading lobes. Stamens ten, downy at the base. Ovary scaly; style glabrous, (s. Cinnabarinum)
R. xanthocodon was discovered by Kingdon Ward out of flower in July 1924, growing on the Nam La, a pass in S.E. Tibet under Namcha Barwa, the mountain which dominates the great bend of the Tsangpo river. He collected seeds in the autumn (KW 6026) and the species was described some ten years later after it had flowered at Bodnant. Unfortunately, Dr Hutchinson placed it in the Triflorum series, thus obscuring its affinity, which is with R. cinnabarinum and R. concatenans. It differs from both in having the leaves scaly above, and in its narrow-campanulate corollas, and from the former also in the colour of the flowers and their smaller size. That is true at least of the type-plant. But other plants raised from KW 6026 approach R. cinnabarinum in the shape of their corollas, and it may eventually prove that the presence or absence of scales on the upper surface of the leaves is not a reliable character.
R. xanthocodon is perfectly hardy in a sheltered place and makes a tall, laxly branched shrub. The colour of the flowers varies somewhat, but is always a pleasant and uniform shade of yellow.
R. concatenans Hutch. – This, another of Kingdon Ward's discoveries, was described in 1935 from a plant at Nymans in Sussex, raised from his seed no. 5874. He found this species (which he nick-named 'Orange Bill') in June 1924, growing in a tanglewood of rhododendrons on a steep slope above the torrent that runs from the Doshong La to the Tsangpo, and gathered seed in the following autumn. 'But I had a really desperate time getting seed of it. It grew, as I say, well up the steep slope and often out of reach on the cliffs above. I went after it on October 22nd during a heavy snowstorm and got a few capsules. On October 26th I tried again; by this time the bushes were well snowed up, but I got some more seed, and it is a relief to think that the seeds are germinating, considering the awful strain on my temper while struggling in that accursed cold muddle' (Riddle of the Tsangpo Gorges, p. 113).
R. concatenans is closely allied to R. cinnabarinum, indeed it is nearer to it than is R. xanthocodon. It differs in the shorter, campanulate corolla and, in the typical state, in its apricot-yellow flowers. A feature of the Kingdon Ward introduction is that the young leaves are verdigris-coloured and remain glaucous above for several months. As in R. cinnabarinum, they are without scales on the upper surface. R. concatenans is a hardy species, flowering in late April or May; it is best placed in a fairly sunny position, as the characteristic leaf-colouring is not developed in shade, or at least is less vivid. Bot. Mag., n.s., t. 634. It received a First Class Certificate when shown from Nymans on May 8, 1935.
R. concatenans was reintroduced by Ludlow, Sherriff, and Taylor in 1938 from the Lo La, some ninety miles to the south-west of the type-locality (L.S. & T. 6560). A plant raised from the seeds by Collingwood Ingram at The Grange, Benenden, Kent, produced flowers described as Chinese Coral suffused red-orange inside, brighter red outside. It received an Award of Merit when exhibited by him in 1954 under the clonal name 'Copper'. According to the field note, the wild plants had apricot-coloured flowers.
From the Supplement (Vol. V)
R. xanthocodon, with R. concatenans, becomes a subspecies of R. cinnabarinum.