|Disease issues:||Viruses can be a problem|
|Bloom season:||Early Spring|
Epimedium, also known as Barrenwort, Bishop's Hat, Fairy Wings, Horny Goatweed, or Yin Yang Huo (Chinese: 淫羊藿), is a genus of about 25 species of herbaceous flowering plants in the family Berberidaceae. They are native to southern Europe, and central, southern and eastern Asia.
Epimediums are low-growing perennials which form dense colonies over time through spreading rhizomes. The leaves are basal, evergreen or deciduous, 2-3 ternate or pinnately compound, held upright on slender but stiff petioles
The flowers are held on delicate racemes or panicles, perfect, bisexual, 4 petals and 8 sepals are distinct and in imbricate rows. The flowers of many species and cultivars have a "spidery" appearance.
About 25 species, including:
- Epimedium acuminatum
- Epimedium alpinum
- Epimedium diphyllum
- Epimedium grandiflorum
- Epimedium leptorrhizum
- Epimedium perralderianum
- Epimedium pinnatum
- Epimedium pubigerum
- Epimedium sagittatum
- Epimedium sempervirens
- Epimedium setosum
- Epimedium sutchuenense
There are also numerous hybrids grown in the garden.
Growing conditions 
Many species, hybrids, and cultivars are grown for ornament, particularly as ground covers for partial shade. They prefer a well-drained, humus-rich soil, but are somewhat adaptable to poorer soils if the drainage is good.
Epimediums need little or no maintenance, but many gardeners cut down the previous year's foliage (even on evergreen species) because the old foliage hides the flowers on many species and cultivars. For this purpose the foliage needs to be cut (not pulled), and care should be taken not to disturb the new growth, which is quite tender. Late freezes can also cause damage to new growth, so some shelter (such as conifer branches) should be applied if a hard freeze is expected.
The evergreen species are particularly good at keeping down weeds; and most species have attractively colored new foliage in spring. One of the more popular cultivars is the Persian barrenwort E. x versicolor 'Sulphureum' (a hybrid of E. grandiflorum x E. pinnatum ssp. colchicum), also known as the Bicolor barrenwort, which produces soft yellow flowers in the spring.
Many species of Epimedium are reported to have aphrodisiac qualities. 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 or pill form and sometimes blended with other supplements. The "active ingredient" in Epimedium is icariin, which can be found in standardized extracts to be from 5% up to 60% potent. Strengths above that are usually reserved for lab use.
In addition to this mechanism, it also acts as a mild PDE-5 inhibitor. PDE-5 is an enzyme which is produced in a 'negative feedback" loop. As more blood flows to the genitals, PDE-5 metabolizes the nitric oxide almost as fast as it is being produced to keep it in check. If the body does not produce enough of this enzyme, damage to the erect penis could result from too hard of an erection. This is called priapism. Viagra, a popular pharmaceutical, works by blocking the production of the PDE-5 enzyme. Horny Goat Weed produces small amount of PDE-5 inhibitors within safe levels.
Pests and diseases 
- Black Vine Weevil: Otiorhynchus sulcatus
- Alternativehealing.org's page on use in traditional Chinese medicine
- IronMagazine's page on Epimedium as a supplement
- Discovery Health Article By Chris Kilham
- William T. Stearn, The Genus Epimedium, revised edition 2002, ISBN 0-88192-543-8