What is Epimedium?

Epimedium is a genus of about 60 flowering herbs, cultivated as a ground cover plant and an aphrodisiac. Many species are endemic to southern China, meaning they grow only there. Other species have a native habitat covering other parts of Asia and Europe. Epimedium plants have common names including bishop's hat, horny goat weed, and yin yang huo.

Plants in the Epimedium genus are very adaptable and grow well in gardens and containers. There are many cultivated hybrids, and the plant's popularity is growing in the West. In the wild, Epimedium grows on the forest floor, and the plants do best in similar environments, including moist, rich soil, cool shade, and shelter from strong winds.

The plants have long been used in Japan as a ground cover for their attractive foliage and flowers, which grow in a wide variety of colors. Most plants bloom in the early spring. The leaves of some species also change color in the fall, while other species retain their leaves year round.

Many species of Epimedium, particularly E. grandiflorum, are used as an aphrodisiac. The common name horny goat weed derives from a legend that the aphrodisiac properties of the plant were first noted by a Chinese goat farmer who noticed an increase in sexual activity in his flock after they ate the herb. The active ingredient in the herb is icariin, which is believed to work by increasing nitric oxide in the body, which leads to the relaxation of smooth muscle tissue, and consequently to increased blood flow to the penis. Unfortunately, the manufacture of horny goat weed supplements has led to over-exploitation of Epimedium populations, any many species are becoming endangered as a result. Instead of being cultivated for medicinal use, most Epimedium used in Traditional Chinese Medicine (TCM) or sold over the counter as a dietary supplement is harvested from the wild.

The herb may also be used to treat osteoporosis, fatigue, memory loss, heart or liver disease, and high blood pressure. Possible side effects include difficulty breathing, nosebleed, vomiting, and dry mouth or thirst. Such side effects are associated with long term or excessive use.

Pregnant women should avoid taking Epimedium. The herb may also have adverse interactions with medications used to treat high blood pressure and prevent clotting, so caution should be taken when combining these medications. It is always important to discuss any herbal supplements or over the counter drugs with one's physician before taking them.