Citron (scientific name: Citrus medica L.), also known as citron or citron seed, is an irregularly branched shrub or small tree. Newborn shoots, buds and flower buds are dark purple-red. Leaves are simple, sparsely and concurrently single-complex, with elliptic or ovate-elliptic blades and shallowly obtusely lobed teeth on the leaf margins. Racemes with up to 12 flowers and 5 petals. Fruit ellipsoid, suborbicular or narrowly fusiform at both ends, weighing up to 2000 g, pericarp yellowish, rough, difficult to peel, flesh colorless, nearly transparent or pale milky yellow, crisp, sour or slightly sweet taste, fragrant; seeds small, smooth, cotyledons milky white, many or single embryo. Fl. April-May, fr. Oct-Nov.

Born in hot and humid environments from 350 to 1750 meters above sea level. It is more widely planted in Taiwan, Fujian, Guangdong, Guangxi, Yunnan, and other provinces and districts of China. It is also found in Vietnam, Laos, Myanmar, and India.

The citron is pungent, slightly bitter, sour, warm in nature; it belongs to the liver, lung and spleen meridians; it is fragrant and dispersing, and can be ascending or descending;

It has the function of dispersing the liver and regulating the qi, broadening the chest and resolving the phlegm, removing the dampness and neutralizing the middle;

It is used in the treatment of distension of the chest and hypochondrium, coughing with much phlegm, plumping in the epigastric region, stagnant appetite and vomiting, and oedema and foot pain.