Ku Shen, the bitterest root

Ku Shen reads “the bitter shen”: the first character names its flavour, the second is the one borne by several great roots of the pharmacopoeia. It is the root of Sophora flavescens, a subshrub of the legume family, with pale yellow butterfly-shaped flowers and pods like strings of beads; its leaves recall those of the Japanese pagoda tree, hence its other names. It grows in almost all of China, with no single reference terroir. The name exaggerates nothing: it is one of the most bitter substances in the whole Chinese pharmacopoeia, and a root that is not frankly bitter is suspect, because bitterness follows the alkaloids.

Clearing Heat, drying Dampness

In Traditional Chinese Medicine, the root is cold and bitter, a single flavour pushed to the extreme. Bitterness dries Dampness and makes things descend, coldness clears Heat, and it does both more strongly than almost any other. Its channels map out its territory: the Large Intestine and Stomach in the Middle, the Bladder and Liver below, that is, the whole route by which tradition lets Damp-Heat out, and the Heart. Tradition directs it above all towards the lower body, where Dampness and Heat mingle and settle, and credits it with promoting the flow of urine.

A root for the skin, to be used with measure

A classical adage holds its logic: Heat generates Wind, Dampness generates what swarms; removing both removes what they produce. Tradition thus credits it with dispersing Wind from the skin, the kind that moves about, and it is among the most used plants of Chinese external medicine, as a wash or a compress. Its harshness means it is used as an assistant rather than as the main plant, and often in pills or powder, so sharp is its bitterness. Modern research is particularly interested in matrine and oxymatrine.