Mu Zei, the “wood thief”

Mu Zei reads “wood thief”, and it is a workshop name: the stem of this horsetail is so rough that woodworkers used it to polish and smooth their pieces, Li Shizhen explains. It files the wood, stealing it in tiny shavings. Its ridges are impregnated with silica, which feels like sand under the teeth, and that is how an authentic stem is recognised. Also known as scouring rush, the plant belongs to one of the oldest plant lineages still living. The best material today is recognised as coming from Liaoning and north-east China.

Dispersing Wind-Heat upward

In Traditional Chinese Medicine, Mu Zei is neutral, sweet and bitter in flavour, and enters the Lung, Liver and Gallbladder. The sweet moderates, the bitter makes things descend; but it is its form that decides: its hollow, jointed, light stem tends to rise and disperse outward, towards the upper body, the head and the eyes. It is traditionally used to disperse Wind-Heat, a gentle dispersal without pungent heat. The Liver, the tradition says, opens into the eyes: it is through the Liver that the herb has its speciality.

Brightening vision

Brightening the eyes is its signature action, the one for which the pharmacopoeia keeps it. The tradition describes a Wind-Heat of the Liver and Gallbladder that makes Blood stagnate in the vessels of the eye; by dispersing it, horsetail lets Blood rise freely to the eye, and the texts make it an essential substance for brightening the eyes. It is readily paired with pipewort (Gu Jing Cao), the other plant pillar of this field. Rougher and more drying than pipewort, it is reserved for robust constitutions, in short courses.