Description from Flora of China
Herbs, perennial. Rhizomes present. Stems erect, simple or branched from base. Basal leaves rosulate, stem leaves alternate and petiolate; leaf blade varying in shape, often hairy, margin toothed or lobed. Inflorescences sometimes scapose. Flowers axillary and solitary or in terminal racemes, pedicellate. Bracteoles present or absent. Calyx 5(-7)-lobed. Corolla purple-red or yellow, tubular; tube slightly curved or straight, dorsiventrally compressed, with 2 plaits from tube base to throat; limb 2-lipped, 5-lobed. Stamens 4, didynamous, rarely 5 and 1 smaller than other 4, included; anthers coherent in pairs, locules fertile. Ovary base with a disc, 2-loculed, rarely 1-loculed; ovules numerous. Stigma 2-lamellate. Capsule with persistent calyx, loculicidal. Seeds minute; seed coat reticulate.
Six species: endemic to China.
Also see post-FOC publication: Li, Xiao-Dong et al. 2011. Taxonomic revision of the genus Rehmannia. Plant Sci. J. 29: 423-431.