Rehmanniaceae
Rehmannia glutinosa
Di huang · Chinese foxglove
- Part used
- root
- Native range
- China
- Morphology
- A low sticky perennial to about thirty centimetres with a rosette of wrinkled leaves and tubular reddish-brown flowers, over a fleshy orange root.
What is in it
Evidence
Very little controlled human evidence. Laboratory work on catalpol is extensive.
Safety
Generally regarded as well tolerated. Digestive upset is the commonest report. Quality and processing vary considerably, and the two forms are not interchangeable.
Regulatory: Permitted as a listed medicine ingredient in Australia.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
In the Shennong Bencao Jing. The distinction between raw and prepared forms is ancient and is treated as fundamental rather than as a detail of processing.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Rehmannia is the clearest case of a tradition treating processing as constitutive rather than incidental. Raw and nine-times-steamed root are not the same medicine, are given different names, have different classified natures, and are prescribed for opposite purposes.
Its family is disputed. APG places Rehmannia among the broomrapes, in Orobanchaceae, and most recent references follow that; GBIF and Kew keep it in a family of its own, Rehmanniaceae. This entry follows its stated authority, as it does for elder, and flags that the commoner label differs.
It is also a nomenclature curiosity. The English common name is Chinese foxglove and it is not remotely a foxglove, though the resemblance of the flower is real — and, following the molecular revision that moved Digitalis out of Scrophulariaceae, the two are not even in the same family any more. Rehmannia landed among the broomrapes, which are mostly parasites.
Nomenclature verified against GBIF backbone taxonomy.