Zao Jiao

Zao Jiao is the dried mature pod of Gleditsia sinensis Lam. (Fabaceae), the Chinese honey locust, a large deciduous tree 15–30 m tall native to China and widely planted in temperate East Asia. The trunk and lower branches bear conspicuous, stout, simple or branched, reddish-brown thorns 5–20 cm long (separately used as Zao Jiao Ci). Leaves are once-pinnately compound with 6–14 ovate-lanceolate, finely crenulate leaflets. Small greenish-white flowers are borne in narrow racemes. The legume is a flat, slightly twisted, dark brown to purplish-black pod 12–30 cm long and 2–4 cm wide, woody, with a thick, sticky, saponin-rich mesocarp enclosing several hard, ellipsoid, dark brown seeds. Pods are collected in autumn and sun-dried. In TCM they powerfully open the orifices, expel phlegm, and dispel obstruction; they are saponin-rich, irritant, and contraindicated in pregnancy and in cases of weakness or bleeding.