Rehmannia is a small genus of seven species of perennial flowering herbs in the family Orobanchaceae, order Lamiales, native to China and Japan. The genus is notable within its family for being non-parasitic — the vast majority of Orobanchaceae are parasitic plants, making Rehmannia an unusual exception. It has been placed as the sole member of the monotypic tribe Rehmannieae, though molecular phylogenetic studies suggest it forms a clade with the closely related genus Triaenophora.
Sometimes called Chinese foxglove because of a superficial resemblance to the genus Digitalis, Rehmannia species are perennial herbs bearing large, showy, tubular flowers. They are cultivated as ornamental garden plants in Europe and North America and hold considerable importance in Asian traditional medicine.
The most economically and medicinally significant species is Rehmannia glutinosa, known in Chinese as dìhuáng (地黄). Its root is a central herb in traditional Chinese medicine, used as the primary ingredient in si wu tang (four substance decoction) — a foundational formulation traditionally considered to support the production of blood, prepared alongside Angelica sinensis (dang gui), Chinese peony (bai shao yao), and Ligusticum striatum (chuan xiong).
Etymology
The genus name Rehmannia honours Joseph Rehmann (1788–1831), a physician who worked in St. Petersburg.
Distribution
Rehmannia is native to China and Japan. The genus is cultivated more broadly as an ornamental in gardens across Europe and North America.
Cultural Uses
Rehmannia glutinosa (dìhuáng, 地黄) has been used in traditional Chinese medicine for centuries. It is the primary ingredient in si wu tang (four substance decoction), prepared with dang gui, Chinese peony, and Ligusticum striatum, a formulation regarded as a fundamental tonic for supporting blood. A related preparation, tao hong si wu tang, adds peach kernel and safflower and is used traditionally for fatigue.
Taxonomy Notes
Rehmannia has been placed as the sole member of the monotypic tribe Rehmannieae within Orobanchaceae. Molecular phylogenetic studies indicate it forms a clade with Triaenophora. Unlike the overwhelming majority of Orobanchaceae, Rehmannia is not parasitic. As of February 2025, Plants of the World Online recognises seven accepted species.
