An evergreen shrub 6 to 7 ft high; young shoots scaly. Leaves oblong-elliptical, tapered at both ends, 3 to 6 in. long, 1 to 2 in. wide, glaucous and with numerous tiny dark scales beneath; stalk 1⁄2 to 1 in. long, not grooved. Flowers usually three or four in a cluster, very fragrant. Calyx large, 5⁄8 to 3⁄4 in. long, deeply five-lobed, the lobes oval, 1⁄3 to 1⁄2 in. wide; flower-stalk 3⁄4 in. long, very scaly. Corolla pure glistening white except for a pale yellow blotch at the base inside, funnel-shaped, five-lobed, 3 to 4 in. long and wide. Stamens ten, 2 in. long, downy on the lower half. Ovary densely scaly; style as long as the stamens, scaly on the lowest third. Seed-vessel 2 in. long, glandular, the calyx persisting at the base. Bot. Mag., t. 9612. (s. Maddenii ss. Megacalyx)
This beautiful species was discovered by Forrest in 1925 on the western flank of the Nmai Hka-Salween divide, upper Burma, growing as a shrub 6 to 7 ft high on the margins of open conifer forest and among scrub at 10,000 to 11,000 ft. He introduced it in the same year. Subsequently Kingdon Ward found it farther west in the Seinghku valley and in the Adung valley nearby, where it makes dense thickets along the river bank at 6,000 ft.
R. taggianum first flowered in the Edinburgh Botanic Garden in May 1930 (under glass), the plant, which had been raised from Forrest's 1925 seed, being then only 18 in. high. It has to be treated as a greenhouse shrub over much of the country, but is grown out-of-doors in a few favoured gardens in the Atlantic zone. A plant shown by the Marquis of Headfort on April 5, 1932, received an Award of Merit. It had been brought into early flower under glass. It was given a First Class Certificate on April 13, 1943, when shown by Murray Adams-Acton. At Brodick in the Isle of Arran, where it grows in the open, its normal flowering time is late May.
R. taggianum is very closely allied to R. lindleyi, but with a more eastern distribution. It differs in having the calyx-lobes without marginal hairs, and in other minor characters.
From the Supplement (Vol. V)
Although the species was described from a specimen collected by Forrest in 1925, Mr Davidian points out that it had been found some five years earlier by Farrer, in the Burma-Yunnan frontier region (Farrer 1825), though it was not introduced by him.
R. headfortianum Hutch., not mentioned in the main work, is now included in R. taggianum. The type was a plant raised at Headfort said to be from KW 6310, collected 'blind' in the early winter during Kingdon Ward's journey through the Tsangpo gorge. If this provenance is correct, R. taggianum extends further west than once supposed, almost into the area of the related R. lindleyi.