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A hybrid between R. arboreum Sm. subsp. delavayi (Franch.) D.F.Chamb. and R. decorum Franch. Shrub or small tree, 1.5-3(-4)m. Leaves coriaceous, 6-11 × 2.5-5cm, upper surface glabrous, with slightly impressed veins, lower surface with a thin veil of dendroid hairs embedded in a surface film, with numerous red punctate hair bases overlying the veins; petioles glabrous. Flowers 10-15, in a dense inflorescence; calyx 2-3mm; corolla 6-7-lobed, rose-pink, usually with darker margins and at least a few crimson flecks, campanulate or tubular-campanulate, with nectar pouches, 40-50mm; ovary stalked-glandular, style glandular, usually almost to tip.
Distribution China (W Yunnan, ?Guizhou).
RHS Hardiness H3.
This hybrid has been mistakenly placed in Subsect. Irrorata, even though the collector of the type specimen, George Forrest, stated that he considered it to be a hybrid between R. delavayi and a species in Subsect. Fortunea. It may be distinguished by the 6-7-lobed corolla and by the leaves that are intermediate between those of the parents. Plants that are undoubtedly referrable to R. × agastum occur with the parents at or close to the type locality and are clearly of hybrid origin. Some plants in cultivation under the name R. agastum belong to R. papillatum.