An evergreen shrub up to 12 ft high; branchlets stout, at first floccose and glandular, soon glabrous. Leaves oblong or oblong-elliptic, acuminate at the apex, rounded at the base, 3 to 5 in. long, 11⁄2 to 13⁄4 in. wide, glabrous above, covered beneath with a thin brown indumentum which gradually falls away, leaving the underside almost glabrous by late summer; petiole 5⁄8 to 11⁄2 in. long, glabrous. Flowers about ten together in a lax truss, opening in May; pedicels up to 2 in. or slightly more long, glandular and floccose. Calyx about 1⁄8 in. long, with five oblong or roundish lobes. Corolla funnel-campanulate, pink with carmine speckling in the throat, five- to seven-lobed, about 3 in. wide. Stamens ten to fourteen, filaments downy in the lower third of their length. Ovary cone-shaped, glandular; style glandular except near the tip. Bot. Mag., t. 9359. (s. Taliense ss. Adenogynum)
R. detonsum was discovered by Forrest in N.W. Yunnan in 1917 on the eastern flank of the Sungkwei range, just west of the Yangtse, and was probably introduced by him from the same area in the same year. It first flowered at Edinburgh in 1917. At its best, as figured in the Botanical Magazine, this is one of the finest species for flower in the Taliense series. The truss figured there is from the Edinburgh plant.
From the Supplement (Vol. V)
A probable natural hybrid of R. adenogynum. A plant raised from seed of typical R. adenogynum matches the type of R. × detonsum (Rev. 2, p. 341).