No matter how long a gardener has been putting trowel to earth, there's always interest in perennials that excel in shade. And therein lies an important distinction, for although many plants can tolerate shade or can be coaxed into a half-hearted shadow display, few actually relish the low light. A list of plants requiring shade to demonstrate their best attributes would be short indeed, but barrenwort (Epimedium spp.) would certainly be front and centre in the shade parade. Naturalized colonies of barrenwort grow best in moist woodlands under the dappled shade of deciduous trees, where the soil is undisturbed and enriched with leaf mould. Their carpet abruptly halts where shade gives way to brighter light. (When grown in full-day sunlight, a martyring regimen of daily irrigation is necessary to keep them happy.)
Before the 19th century, barrenwort proliferated only in China—which escaped the huge glacial flows that obliterated the plant from most of the European and American continents—in shady valleys and on north-facing mountain slopes, breeding themselves through centuries of seclusion. (The shy Vancouveria is its only North American cousin, and represents a prehistoric relationship to Epimedium.) Some specimens were sent back to Europe by adventurer-botanists in the early 1800s, when plant travel from Asia to Europe took six months by boat (shipments of 1,200 plants leaving China were reduced to 260 live specimens on arrival in England). Victorian gardeners filled their dark corners with the obliging barrenworts; Gertrude Jekyll grew Epimedium pinnatum, with its orchid-like spikes of pale yellow bloom that she found “very useful for combining with greenhouse flowers of delicate texture.” It wasn't until after 1979, when the Chinese Cultural Revolution ended, that new species and hybrids began to appear in the West. Of the recognized 44 species of Epimedium, 36 were discovered and documented after 1975.
“Barrenwort” refers to the plant's pharmaceutical properties and association with human fertility. In medieval times it was thought to prevent conception and suppress the breasts of virgins, while in other centuries barrenwort was considered a stimulant to the libido, hence the species known as horny goat weed (E. sagittatum), which explains its use in herbal medicine—and leaves little to the imagination. But gardeners are more likely to know Epimedium as bishop's hat (E. grandiflorum), describing the racemes of charming, mitre-like flowers that dangle and dance about in early spring breezes. Like other perennials with thin, wiry stems (coral bells, columbines, Siberian bugloss), bishop's hats seem to hover, ethereally suspended in flight over their clumps of arrow- or heart-shaped leaves.