Rehmannia

Rehmannia original: 地黃 (Dihuang); Rehmannia glutinosa grows in the river valleys and marshes of Xianyang; those harvested from yellow soil are of the best quality. It is now found in many regions, though the variety from Tongchuan is considered the most superior.

In the second lunar month, the leaves emerge and spread across the ground. They resemble the leaves of the Plantain original: 車前 (Cheqian); a common medicinal weed, but the surface is wrinkled and not glossy. Taller plants reach over a foot in height, while shorter ones are only three or four inches tall. Its flowers resemble those of the sesame plant and are reddish-purple, though some plants produce yellow flowers. The fruit forms a capsule similar to that of Forsythia original: 蓮翹子 (Lianqiaozi); the seeds are very fine and brown in color.

The roots resemble human fingers and are entirely yellow, though their thickness and length are not uniform. The roots are harvested in the second and eighth lunar months. If the roots are steamed until they are thoroughly soft and then dried in the sun, they are called Processed Rehmannia original: 熟地黃 (Shu Dihuang). Those dried in the shade are called Raw (Dried) Rehmannia original: 生地黃 (Sheng Dihuang).

Physicians distinguish the quality of the roots by soaking the freshly harvested batch in water. Those that float are called "Heavenly Yellow" original: 天黃 (Tianhuang) and are unfit for use. Those that half-sink are called "Human Yellow" original: 人黃 (Renhuang) and are considered secondary in quality. Those that sink completely to the bottom are called "Earth Yellow" original: 地黃 (Dihuang) and are the very best.

The plant is also known as "Earth Marrow" original: 地髓 (Disui), Xia original: 芐, or Ba original: 芭. It is used to treat palpitations caused by fright, consumptive fatigue, the vomiting of blood, nosebleeds, and uterine bleeding or blood circulation issues in women.

When dried in the sun, the herb’s nature is balanced; when dried over a fire, its nature is warm. One must strictly avoid using iron vessels when preparing this medicine. Traditional Chinese pharmacy often warns against iron contact for certain herbs to prevent "tainting" the medicinal essence or causing adverse chemical reactions.