Epimediums are hardly commonplace plants in the United States, but they should be. As more and more new species and varieties are being discovered in Asia, a few of us nurserymen are doing what we can to make this genus more of a presence in American gardens. I recently returned from China, where I spent a month exploring hillsides in search of epimediums.
Although often mistaken for orchids because of their flowers, epimediums are members of the barberry family (Berberidaceae). These spring-blooming perennials combine well with ferns, hostas, lungwort (Pulmonaria spp. and cvs.), hardy gingers, and other shadegarden plants. Depending on the species, the number of flowers produced per plant can vary from just a few to literally hundreds covering a single stem. Flower color runs the gamut from white, pink, rose, and purple to yellow, orange, and red. And the flowers can be solid, bicolored, or a combination of several colors. Individual flowers last for three days, then shatter, to be replaced by new flowers along the stem. Epimedium foliage can be deciduous, semi-evergreen, or truly evergreen, depending on the species or hybrid and the climate in which it is grown. The leaves are made up of leaflets, which can range in number from 3 to 50 and in size from as tiny as a sparrow’s egg to 6 inches long. They are generally heart-shaped, but can range from round to arrow-shaped. Epimediums vary in habit from clumping types, which reach 6 inches across after three years, to spreaders, which travel by rhizomes up to 12 inches in one year and form dense mats of impenetrable foliage. Before I attempt to grow an epimedium I’m unfamiliar with, I try to learn what I can about its native habitat. Of the 30 or so species of epimedium I have observed in the wild, most seem to thrive in rich, organic loam on gentleto- steep northeast- or northwest-facing slopes, in dappled shade. But I have also seen epimediums growing well in gravel and clay soils, in moist and dry sites, in the cracks of wet limestone cliffs in almost full sun, and in the deep shade of a Cryptomeria forest in highly organic soil.
When growing in deep shade, either in the wild or in the garden, plants are generally taller, have larger leaflets, and are slower to form large clumps than are those in dappled shade. They also have fewer flower stems per plant. In my garden in Massachusetts, epimediums that get four to five hours of direct sun are shorter, much more floriferous, and produce smaller leaflets. However, plants sited in direct sun require adequate moisture in the heat of summer, or the leaves may burn. In southern gardens, epimediums are best kept in the shade.
One of the best traits of epimediums is that they are relatively free of pests and problems. They are, however, susceptible to several foliar viruses that are usually transferred by unclean dividing practices. Plants with mosaic patterns of yellow or cream on the leaves are probably infected and should be discarded.
Unlike many perennials, epimediums can last for decades with minimal care. The one thing I may do is cut back the previous year’s foliage in early spring before the new growth emerges. But, if last year’s evergreen leaves are still attractive, they can be left, and the new leaves will rise above the old stems. A light dressing of an organic or slow release fertilizer low in nitrogen followed by a top dressing of organic matter each spring is about all they need. Epimediums are self-sterile (they won’t set seed unless pollinated by another plant), and breeding from seed is complicated. The plants cannot be rapidly propagated through tissue culture or stem cuttings, either. Division of a rhizome is the most effective method of propagation. On clumping varieties, however, this process is very slow, so these types of epimediums command higher prices. Deciduous species can be divided in either spring or fall, while evergreen species perform better when divided from late August into September. In the rush to cash in on the increasing interest in epimediums, some nurseries have resorted to buying wholesale quantities of plants from disreputable sources. They often end up with inferior plants that are incorrectly named or plagued by viruses. In the case of the newer Chinese species, they buy plants collected in the wild and immediately resell them to the public without propagating, evaluating their performance, and ensuring proper identification.
Being patient about propagating epimediums will help preserve wild populations and will ensure quality plants. As more gardeners fall in love with epimediums, as I have, they are destined to become garden staples.