Epimedium grandiflorum

Epimedium grandiflorum, the large flowered barrenwort, or bishop's hat, is a species of flowering plant in the family Berberidaceae, native to China, Japan and Korea. It is known as "dâm dương hoắc" in Vietnamese.
Description.
It is a deciduous perennial growing to , with bright red stems with green heart-shaped leaves (copper-tinged when young) which are slightly hairy on the bottom. In spring it produces pink, white, yellow or purple long-spurred flowers.
Cultivation.
Numerous cultivars have been selected for garden use, of which the following have gained the Royal Horticultural Society's Award of Garden Merit: 
Traditional Chinese medicine.
"E. grandiflorum" may have anti-impotence properties due to the presence of icariin, a relatively weak inhibitor of PDE5 in comparison to substances like sildenafil (viagra). Western peer-reviewed research into the efficacy of "E. grandiflorum" as an aphrodisiac is lacking; however, the herb has been used for this purpose in traditional Chinese medicine and is a common ingredient of herbal remedies for impotence. It is commonly packed in a capsule with other ingredients or sold as herbal flakes or powder with the name "horny goat weed".