An evergreen shrub 6 to 8 ft, sometimes 10 ft high, of loose habit; young shoots at first very hairy. Leaves leathery, oval-ovate, slenderly pointed; 31⁄2 to 5 in. long, 11⁄4 to 21⁄2 in. wide, dark green and ultimately glabrous above, but sprinkled with long hairs when young and hairy on the margins; scaly beneath; stalk about 1⁄4 in. long and clothed with shaggy hairs like the young shoot. Flowers rich yellow, seven to ten of them closely packed in a terminal cluster, opening in April and May. Calyx membranous, deeply five-lobed, the lobes broadly ovate, rounded, 1⁄4 in. long, sparsely hairy on the margins. Corolla 1 to 11⁄2 in. wide, bell-shaped at the base, separating into five broad, rounded lobes; scaly outside. Stamens ten, their stout stalks very hairy at the lower half; anthers standing just clear of the corolla-tube. Ovary 1⁄4 in. long, conical, closely covered with scales, surmounted by a glabrous, thick, much decurved style. Bot. Mag., t. 7149. (s. and ss. Boothii)
A little-known species, discovered by Thomas Booth on December 16, 1849, in an outer range of the Assam Himalaya, north-west of Tezpur, growing epiphytically on oaks at about 5,000 ft, and introduced by him. R. camelliiflorum and R. edgeworthii also grew as epiphytes in the same locality. He wrote in his journal: 'found many on old decayed and blown down trees on the ground, destitute of seeds or flower buds. With great difficulty and delay I obtained seed of these species by climbing such trees as were practicable, and cutting off the boughs on which they were located' (Gard. Chron., 1862, p. 406). It was found again in the same area but farther north by Kingdon Ward in 1935 (fruit) and 1938 (flower), between Tembang and Lagam (Assam Adventure, p. 266; Gard. Chron., Vol. 102 (1937), p. 143).
R. boothii is not hardy near London, but has been successfully grown in the open air in the south-west. It is however very rare in cultivation. Its flowers and trusses are small, but attractive in the uncommon colour.
R. mishmiense Hutch. & Ward – It is doubtful whether this rhododendron is really specifically distinct from R. boothii, though it differs in having the pedicels villous, instead of bristly as in that species. It was introduced by Kingdon Ward from the Mishmi Hills, Assam, in 1928. An Award of Merit was given in 1940 to a plant under this name but Kingdon Ward, who saw it, appears to have doubted whether it was his R. mishmiense. He described it (the plant exhibited) as having flowers 'of a muddy or pasty margarine-yellow, with a dull crimson rash of measles' (Gard. Chron., Vol. 107 (1940), p. 323). The plants he saw in the wild had lemon-yellow flowers.
From the Supplement (Vol. V)
[R. mishmiense]. – Included in R. boothii.