Rehmannia glutinosa is a perennial herb that is native to China and is commonly used in traditional Chinese medicine. It is typically grown in well-drained, loamy soils with a pH between 6.0 and 7.0.
Rehmannia plants prefer full sun exposure, but can tolerate partial shade. They require moderate to high amounts of water and can tolerate drought conditions. They can grow in a wide range of temperatures, but prefer temperatures between 60-80°F. They are also frost-tolerant, and can survive temperatures as low as -22°F.
Rehmannia plants can be propagated from seed or from root cuttings. They typically take 2-3 years to reach maturity, at which point they will produce flowers and seeds. The root of the plant is the part used for medicinal purposes. The root should be harvested when the plant is 2-3 years old, ideally in the fall, when the plant is dormant. The root is washed, dried and then used for medicinal purposes.
It's important to note that the plant is considered as endangered in the wild, and the cultivation of the plant is considered as a way to preserve the species. Additionally, the plant is sensitive to pollutants, so it should be grown in an organic and sustainable way.
In Traditional Chinese Medicine (TCM), Shu Di Huang (Rehmannia glutinosa, cooked) is typically prepared by first cleaning and drying the root before use. The root is then sliced and then cooked with other herbs such as Shan Yao, and Shan Zhu Yu. This process is called "prepared Rehmannia" or "prepared Rehmannia root" which is believed to make it more easily digestible and also to enhance its medicinal properties. It is also said to make it less cooling and drying to the body, so it can be safely used by people with a yin deficiency.
Another way is to make a tincture, where the root is soaked in alcohol to extract its medicinal properties. This tincture can then be taken as a liquid extract, or added to other formulas.
Shu Di Huang is believed to nourish the blood, support the liver and kidneys, and improve the functions of the heart and brain. It is commonly used to treat a variety of health conditions, particularly those related to blood deficiency, such as anemia, fatigue, and menstrual disorders.
It's important to note that Di Huang Shu is considered a relatively mild herb, and should be taken under the guidance of a qualified practitioner of TCM.