Zhi Ke

Citrus aurantium, the bitter or Seville orange, is an evergreen tree in the Rutaceae family, originally native to Southeast Asia and now widely cultivated in subtropical regions including the Mediterranean and southern China. It typically grows 4-10 meters tall with a rounded crown, smooth grey-green bark, and sharp axillary spines on younger branches. The alternate leaves are ovate to elliptic, 7-10 cm long, dark glossy green, with finely crenate margins and broadly winged petioles. Fragrant white flowers, 2-3 cm across with five petals, are borne singly or in small clusters; they are intensely aromatic. The fruit is a globose hesperidium, 7-8 cm across, with a thick, rough, orange-red rind and acidic, bitter pulp. In TCM, the nearly ripe or just-ripe fruit, dried and sliced (Zhi Ke), is used as a bitter, acrid, slightly cold herb that regulates qi, eases the chest, and disperses focal distention.