Epimedium
Epimedium grandiflorum
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Ranunculales
Family:	Berberidaceae
Genus:	Epimedium L.
Species
About 60 species in cultivation, including: Epimedium acuminatum Epimedium alpinum Epimedium brachyrrhizum Epimedium brevicornu Epimedium campanulatum Epimedium chlorandrum Epimedium davidii Epimedium diphyllum Epimedium dolichostemon Epimedium ecalcaratum Epimedium elongatum Epimedium epsteinii Epimedium fangii Epimedium flavum Epimedium franchetii Epimedium grandiflorum Epimedium ilicifolium Epimedium latisepalum Epimedium leptorrhizum Epimedium lishihchenii Epimedium membranaceum Epimedium mikinorii Epimedium myrianthum Epimedium ogisui Epimedium pauciflorum Epimedium perralderianum Epimedium platypetalum Epimedium pinnatum Epimedium pubescens Epimedium pubigerum Epimedium rhizomatosum Epimedium sagittatum Epimedium sempervirens Epimedium setosum Epimedium sutchuenense Epimedium truncatum Epimedium wushanense

Epimedium, also known as Rowdy Lamb Herb, Barrenwort, Bishop's Hat, Fairy Wings, Horny Goat Weed, or Yin Yang Huo (Chinese: 淫羊藿), is a genus of about 60 or more species of herbaceous flowering plants in the family Berberidaceae. The large majority are endemic to southern China, with further outposts in Europe,^[1] and central, southern and eastern Asia.

Epimedium species are hardy perennials. The majority have four-petaled "spider-like" flowers in spring. Many are believed to be aphrodisiacs, particularly horny goat weed.^[2]

Cultivation[link]

Some varieties and hybrids have been in Western cultivation for the last 100 to 150 years. There are now a wide array of new Chinese species being cultivated in the west, many of which have only recently been discovered, and a number of which have yet to be named. There are also many older Japanese hybrids and forms, extending the boundaries of the genus in cultivation. Few genera of plants have seen such a dramatic increase in new species, primarily thanks to the work of Mikinori Ogisu of Japan and Darrell Probst of Massachusetts. The majority of the Chinese species have not been fully tested for hardiness or indeed for any other aspect of their culture. The initial assumption that the plants would only thrive where their native conditions could be closely replicated have proven to be overly cautious, as most varieties are proving extraordinarily amenable to general garden and container cultivation.

Epimedium x versicolor

Hybrids include Epimedium versicolor (see illustration).

Propagation[link]

While they can be successfully propagated in early spring, Epimedium are best divided in late August, with the aim of promoting rapid re-growth of roots and shoots before the onset of winter. Several breeders (in particular Darrell Probst, Tim Branney & Robin White) have also undertaken their own hybridization programmes with the genus Epimedium. Various new nursery selections are gradually appearing in the nursery trade, the best of which are extending the colour and shape range of the flowers available to the gardener.

Wikimedia Commons has media related to: Epimedium

Garden uses[link]

Hugely popular as garden plants for centuries in Japan, Epimedium are only just beginning to garner attention in the West. While they vary somewhat in their respective hardiness, all are essentially dwellers of the forest floor, and, as such, all require fundamentally similar conditions of moist, free draining, humus rich soil and cool shade, with some shelter for the newly emerging leaves. Some of the more robust varieties are often recommended as plants for dry shade, and whilst their tough foliage and stout rhizomes can allow them to grow successfully in such conditions, (and in more open, exposed positions too, in some instances) they will certainly not give their best. Furthermore, dryness and exposure will pretty much guarantee the early death of many of the newer and more delicate species.

Given suitable conditions most Epimedium will form beautiful ground cover plants, often with magnificent new leaves tinted in bronze, copper and reds combining with a huge variety of flower colours and forms in spring. Handsome and dense-growing foliage remains present for much of the year, with the leaves often turning purple, crimson and scarlet in autumn in some forms, and remaining evergreen in others. With all varieties, however, the foliage is best cut off at ground level shortly before new leaves emerge, so as to fully reveal their beauty of form and colour. Ideally, a mulch should then be applied to protect the new growth from frosts.

Flower forms[link]

Epimedium alpinum flower

From the gardeners point of view Epimedium flowers comprise two main parts, the inner sepals, which are petal-like and four in number (the four outer sepals are small, insignificant, and rapidly shed as the flowers open) and the petals, which are held within the sepals. In some species these petals have developed long spurs and in such plants they greatly exceed the size of the surrounding sepals, producing a flower shaped like an inverted crown, and also giving rise to one of the common names for Epimedium- bishops hat. In other species, however, (such as E. perraldianum) the petals are reduced to tiny spurs, and it is the greatly enlarged and highly coloured sepals that have expanded to catch the attention of the wandering insect.

Medicinal uses[link]

Aphrodisiac[link]

Many species of Epimedium have aphrodisiac qualities associated with content of icariin. According to legend, this property was discovered by a Chinese goat herder who noticed sexual activity in his flock after they ate the weed. It is sold as a health supplement; usually in raw herb, tablet, or capsule form and sometimes blended with other supplements. The over-exploitation of wild populations of Epimedium for use in traditional Chinese medicine is having potentially serious consequences for the long-term survival of several species, none of which is widely cultivated for medicinal purposes.

The "active ingredient" in Epimedium is icariin,^[3] which can be found in standardized extracts from 5% up to 60% potent. Strengths above that are usually reserved for lab use.

Icariin is purported to work by increasing levels of nitric oxide, which relax smooth muscle. It has been demonstrated to relax rabbit penile tissue by nitric oxide and PDE-5 activity.^[4] Other research has demonstrated that injections of Epimedium extract directly into the penis of the rat results in an increase in penile blood pressure.^[5]

Like sildenafil (the erectile dysfunction drug commonly sold as Viagra), icariin, the active compound in Epimedium, inhibits the activity of PDE-5. In vitro assays have demonstrated that icariin weakly inhibits PDE-5 with an IC₅₀ of around 1 μM,^[6][7] while sildenafil has an IC₅₀ of about 6.6 nM (.0066 μM) and vardenafil (Levitra) has an IC₅₀ of about 0.7 nM (.0007 μM).^[8] Measured differently, the EC₅₀ of icariin is approximately 4.62 μM, while sildenafil's is .42 μM.^[9] With the weak potency of Epimedium, and its unknown oral bioavailability, the amount of Epidemium extract necessary to have any effect is unclear from the literature.

A recently published Italian study modified icariin structurally and investigated a number of derivatives.^[10] Inhibitory concentrations for PDE-5 close to sildenafil could be reached. Moreover, the most potent PDE-5 inhibitor of this series was also found to be a less potent inhibitor of phosphodiesterase-6 (PDE-6) and cyclic adenosine monophosphate-phosphodiesterase (cAMP-PDE), thus showing it to have more specificity for PDE-5 than sildenafil.

Epimedium has been shown to up-regulate genes associated with nitric oxide production and changes in adenosine/guanine monophosphate balance in ways that other PDE5 inhibitors do not. Epimedium may have potential to help sexual dysfunction and osteoporosis.^[11]

Epimedium was used in a patent infringement case to rescind parts of the U.S. Viagra patent based on historic use in Chinese medicine. The specific claim was that Viagra was the first medical example of a PDE5 inhibitor which treated erectile dysfunction and therefore claimed patent protection from all similar PDE5 inhibitors. Patent examiners used Epimedium as an example of prior use and rescinded those portions of the patent, however, the Viagra patent still protects the manufacturing process and/or chemical formula for sildenafil. ^[12]

Osteoporosis[link]

Animal studies indicate that Icariin also stimulates osteoblast activity in bone tissue, leading to the development and marketing of medicinal products based on Epimedium extracts for treatment of osteoporosis.^{[13][14][15][16][17][18]}

Chemistry[link]

Epimedium wushanense,contains a number of flavanoids. A total of 37 compounds were characterized from the underground and aerial parts of the plant. Among them, 28 compounds were prenylated flavonoids. The predominant flavonoid, epimedin C, ranged from 1.4 to 5.1% in aerial parts and 1.0 to 2.8% in underground parts.^[19]

Literature[link]

• Epimedium Care and Culture(Heronswood Nursery)
• William T. Stearn, The Genus Epimedium, revised edition 2002, ISBN 0-88192-543-8
• An Overview of Epimedium, in The Plantsman, March 2010, by Tony Avent of Plant Delights Nursery

References[link]