Rehmannia, “the yellow of the earth”

Di Huang, the Chinese name for rehmannia, reads “the yellow of the earth”. The Ben Cao Gang Mu gives its origin: the fresh roots were plunged into water to sort them, and those that sank, the best ones, were called “yellow of the earth”; even today, a good dried root sinks in water. Rehmannia glutinosa is a low perennial whose leaves, covered in glandular hairs, are sticky to the touch, hence its species name. Its reference growing region is Henan, around the former prefecture of Huaiqing, where it ranks among the “four great Huai herbs”. Sheng Di Huang refers to the dried, unprocessed root.

Clearing Heat, nourishing Yin

In traditional Chinese medicine, the raw root is cold, with a sweet and bitter flavour. Sweetness nourishes and moistens, bitterness and cold clear Heat: the whole root lies in this balance. It is associated with the Heart, which governs the Blood, the Liver, which stores it, and the Kidney, where tradition places the deepest reserves of Yin. It is traditionally used to clear Heat and cool the Blood, and to nourish the Yin and generate the Fluids. When Yin is lacking, tradition speaks of an “empty” Heat: what cools is missing. Cooling without drying, nourishing without warming: that is what makes it precious when Heat and a lack of Yin go together.

Raw or prepared: two different roots

Tradition speaks of “one source, three natures”. Fresh, the root is at its coldest; dried, it is Sheng Di Huang, which nourishes the Yin and generates the Fluids while cooling the Blood; steamed with rice wine until black and glossy, it becomes Shu Di Huang, slightly warm, which nourishes the Blood and the Essence. Li Shizhen sums it up: raw, it cools the Blood; prepared, it supplements the Kidney. The two are not interchangeable. The raw root is readily combined with Xuan Shen and Mai Dong to generate the Fluids. Modern research is particularly interested in catalpol, more abundant in the root from Henan.

Key benefits

Yin nourished & Fluids preserved

Sweet and moistening, the raw root nourishes the Yin and generates the Fluids, reaching the body’s deep reserves through the Kidney.

Coolness & Heat cleared

Cold and bitter, it clears Heat and cools the Blood, without drying.

Dryness soothed

When Heat has dried out the Fluids, it gives moisture back to the body and moistens the Intestines, according to Chinese tradition.