Epimediums: Queens of the Woodland

[sidebar]Epimedium flowers demand close examination, as the floral interest of the various species is not always determined by the same flower part. Without exception, all Epimedium species possess two sets of four sepals, and four petals. The outer sepals, similar to bud scales, protect the flower in bud and are shed upon opening. In some species, the inner sepals are expanded and colorful (rarely spurred), whereas the petals are quite small. In others, the sepals are small while the petals are large and colorful, possessing a distinctive spur- or horn-shaped appendage that entices pollinating insects to the nectar produced inside.

Daniel J Hinkley, The Explorers’s Garden 1999 [/sidebar]

Among the most beautiful and charming perennials in the woodland is the epimedium. The delicate early spring bloom and the lovely, yet unobtrusive foliage are assets in any shady garden. Since the 1980s, these useful plants have undergone a transformation in variety and availability. New species have been introduced, and more are to come. The new selections and hybrids now appearing expand the range of color and form in flowers as well as in leaves. Variegation and mottling can now be enjoyed on dramatic elongated leaves with boldly serrate margins.

The Elisabeth C Miller Botanical Garden’s obsession with epimediums began with Mrs Miller’s strong interest in groundcovers. She found Epimedium xperralchicum, E. xversicolor ‘Sulphureum’, and E. xrubrum to be tough, drought tolerant, and attractive; their thick network of roots and rhizomes were ideal for keeping weeds under control. Since those early acquisitions, the garden staff has eagerly been seeking out new taxa in this genus. We now have around 130 named species and cultivars in our collection, as well as several promising seedlings yet to reach flowering stage. The performance of these plants in the Miller Garden has been variable. In recent years, we have begun to sort out the best from the indifferent, and to identify a few cultural quirks to get the most from this genus.

The natural distribution of Epimedium falls in two broad areas—the lands around the Mediterranean Sea, and Eastern Asia. Much of what has been in cultivation for years is derived from Mediterranean species. The winter rain and summer drought with which these epimediums evolved makes them good performers in many Western gardens. These species and their hybrids generally show excellent drought tolerance and have a carefree nature.

A multitude of new epimediums, recently introduced from Asia, has energized the genus. Colorful new growth, interestingly shaped leaves, and heavy flowering have lead gardeners to lust after these plants. These Asian species do not, however, share the drought tolerance and ironclad constitution of their Mediterranean counterparts; they prefer rich soils with regular moisture during the spring and summer growing season.

Cultural Tips

All epimediums thrive in dappled or open shade. In cooler climates, most will tolerate a half-day of sun without damage to the foliage. The more sun they receive, the more water they will need to prevent the leaves from yellowing or burning during dry weather. Although several species will tolerate poor soils, particularly those from the Mediterranean, it is best to provide rich, well-draining soil with plenty of organic matter.

Epimedium leaves may be evergreen or deciduous. Deciduous selections can be cut to the ground as soon as the foliage starts to fade. Evergreen types should be cut back in mid- to late winter to maintain a clean and tidy appearance; this will also allow the flowers to show at their best. At the Miller Garden, we often apply a light topdressing of compost in winter to protect the emerging flower buds.

The Best for Flowers

The early spring bloom of Epimedium is a delight. The slender, delicate stems sparkle with colorful spider-like flowers, generally held well above the foliage. The best flowering epimediums, from our experience at the Miller Garden, can be considered in two categories: those with big flowers, and those with prolific flowers. The flowers of E. brachyrrhizum, E. leptorrhizum, and E. latisepalum dwarf most others. Epimedium brachyrrhizum and E. leptorrhizum are similar in appearance, both low-growing evergreen spreaders. Their soft pink to pale rose flowers are held six to eight inches above the ground and are one-and-a-half to two inches across—huge by epimedium standards. A rare species, E. latisepalum bloomed for the first time for us in spring 2007. The flowers were simply enormous, reaching two inches across in soft white tones; wide sepals give an unusually full appearance to the flower. They were truly a spectacular sight.

The flowers of Epimedium epsteinii and E. franchetii are a little smaller, only one to one-and-a-half inches across, but the plants bloom more prolifically. The sepals of E. epsteinii are pure white and one of the widest in the genus; the inner spurs are a rich red purple. The contrast is magnificent. Epimedium franchetii has luminescent pale yellow sepals and primrose spurs tinted with green. The flowers are held prominently above the apple green spring foliage, showing them to full advantage.

Some of the most prolific floral displays are from Epimedium grandiflorum and E. xyoungianum. Their individual flowers are not large, but they occur in profusion, often creating a cloud of color above the leaves. In the garden, they behave much the same, growing into tight clumps around twelve to fifteen inches tall. Most are deciduous, and the few that are semi-evergreen generally need to be cut back by early winter. In the last ten years, both species have had several cultivars introduced that are great improvements over older ones. Among our favorite cultivars of E. grandiflorum are ‘Album’, ‘Lavender Lady’, ‘Purple Prince’, and ‘Tama-no-genpei’. Epimedium xyoungianum is a hybrid between E. grandiflorum and E. diphyllum. Some of its best cultivars are ‘Benikujaku’ and ‘Murasaki-juji’ for rich rose purple flowers, ‘Tamabotan’ for pink flowers, and ‘White Star’ and ‘Yenomoto’ for a flurry of white flowers.

The Best for Foliage

Flowers are only half the story with epimediums. They are often listed among the best foliage plants for the garden. New spring growth may be bronzy, coppery, pink, or red; leaves with spotting, mottling, or white variegation are also available. Epimedium dolichostemon, E. membranaceum, E. myrianthum, E. pubescens, and E. rhizomatosum display eye-catching maroon mottled patterns on their new spring leaves. The patterns fade as the leaves mature, but will often return less intensely following a spell of cold weather in fall. I find E. lishihchenii particularly attractive; its new growth is a bronzy salmon, with sulfur yellow flowers floating above; the mature foliage deepens to dark green with a blue green underside. The rich purple chocolate leaves of E. grandiflorum ‘Dark Beauty’ and ‘Royal Flush’ are sensational; both cultivars produce two or three flushes of colored foliage from spring to mid-summer.

Drought Tolerant Selections

Epimedium xperralchicum is one of the toughest and most durable species. Bright yellow flowers herald spring; evergreen leaves and a spreading habit make it an excellent weed barrier. A vigorous grower, it will spread almost a foot a year. It is often mislabeled and sold under one of its parents’ names, E. perralderianum or E. pinnatum subsp. colchicum. Fortunately, there are only minor differences between these plants and they are all tough and resilient choices for drier situations. Now commonly available, the cultivar ‘Fröhnleiten’ has reddish bronze new growth with bright green veins.

Also known for its drought tolerance, Epimedium xversicolor is a garden hybrid between E. grandiflorum and E. pinnatum subsp. colchicum. The two most common cultivars, ‘Neosulphureum’ and ‘Sulphureum’, have soft yellow flowers that offer a contrast with the red-flushed new foliage. Less widely available are the cultivars ‘Cherry Tart’, ‘Cuprea’, and ‘Versicolor’; their flowers range from salmon pink to rose, with attractive new foliage.

At the Miller Garden, we have a fondness for Epimedium xrubrum ‘Sweetheart’. Hardy and rugged, it hides its toughness behind dainty rose red flowers and lovely, bright green leaves edged in red. This hybrid species is a great choice for a groundcover, so thick and dense that weeds can rarely push through. Flowers of an unusual orange color are the highlight of E. xwarleyense. Discovered at Warley Place in England, the home of Miss Ellen Willmott, this tolerant hybrid slowly forms somewhat open clumps. The cultivar ‘Orangekönigin’ (‘Orange Queen’) offers slightly paler flowers and tighter growth habit.

Looking to the Future

The allure of epimedium’s delicate flowers is undeniable. The general ease of culture and their usefulness in the garden makes them a must for anyone with a bit of shade. With such variety available to us, hybridizing is beginning to catch on with growers and collectors. We are going to see an explosion of new and better plants in our nurseries in the coming years. Epimedium ‘Amber Queen’ is an excellent example of a recent hybrid slowly finding its way into gardens. Its new foliage is heavily flecked in maroon, contrasting and highlighting the airy sprays of spidery, one-inch amber yellow flowers. The peak of bloom is in April, but repeat flowering occurs until mid-summer.

Looking at the seedling beds of a few Northwest enthusiasts has only confirmed that the world of epimediums is going to get even better. Imagine hundreds of plants combining heavy flowering, larger blooms, tight clumpers, slow spreaders, and a fantastic array of foliage—a veritable bed of oysters waiting for the pearls to be plucked from their shells.

Recommendations from the Miller Garden

After years of cultivating and observing Epimedium species, hybrids, and cultivars at the Elizabeth C Miller Botanical Garden, the staff has assembled the following lists of recommended epimediums. The majority of them are adapted to Sunset zones 2-9 and 14-17, and are considered hardy in USDA zones 5-9; exceptions are noted below. This essentially covers most of the West Coast from San Francisco north to British Columbia. Those selections that are reliably drought tolerant are so noted. Most of the epimediums listed are clumpers; the ones best used for ground covering purposes are noted as “spreader.”

The best epimediums for all around garden use

Epimedium ‘Black Sea’ (drought tolerant, slow spreader)
Epimedium grandiflorum ‘Irene’
Epimedium grandiflorum ‘Queen Esta’
Epimedium grandiflorum ‘Tama-no-genpei’
Epimedium grandiflorum var. higoense ‘Bandit’
Epimedium grandiflorum var. higoense ‘Saturn’
Epimedium grandiflorum var. thunbergiana ‘Yubae’ (also sold as ‘Rose Queen’)
Epimedium pauciflorum (spreader)
Epimedium xperralchicum (drought tolerant spreader)
Epimedium perralderianum (drought tolerant spreader)
Epimedium pinnatum subsp. colchicum (drought tolerant spreader)
Epimedium platypetalum × pauciflorum (spreader)
Epimedium xrubrum (USDA 4-9; drought tolerant spreader)
Epimedium sempervirens ‘Okuda’s White’ (slow spreader)
Epimedium sempervirens ‘Rose Dwarf’
Epimedium stellulatum (USDA 4-9)
Epimedium xversicolor ‘Cherry Tart’ (slow spreader)
Epimedium xversicolor ‘Neosulphureum’ (drought tolerant spreader)
Epimedium xversicolor ‘Sulphureum’ (drought tolerant spreader)
Epimedium xversicolor ‘Versicolor’ (drought tolerant spreader)
Epimedium xwarleyense (drought tolerant spreader)
Epimedium xwarleyense ‘Orangekönigin’ (drought tolerant spreader)

The best epimediums for foliage

Epimedium brevicornu (USDA 4-9)
Epimedium dolichostemon
Epimedium grandiflorum ‘Dark Beauty’
Epimedium grandiflorum var. violaceum ‘Bronze Maiden’
Epimedium lishihchenii (USDA 4-9)
Epimedium myrianthum ‘Mottled Madness’
Epimedium pubescens (USDA 6-9)
Epimedium xrubrum ‘Sweetheart’ (USDA 4-9; drought tolerant, slow spreader)
Epimedium sagittatum
Epimedium sempervirens ‘Cherry Hearts’
Epimedium sempervirens ‘Variegata’
Epimedium ‘Starlet’
Epimedium xyoungianum ‘Copper Charm’
Epimedium xyoungianum ‘Freckles’
Epimedium xyoungianum ‘Jenny Wren’

The best epimediums for flowers

Epimedium brachyrrhizum (USDA 5-8; spreader)
Epimedium epsteinii (slow spreader)
Epimedium franchetii (USDA 6-9)
Epimedium grandiflorum ‘Album’
Epimedium grandiflorum ‘Lavender Lady’
Epimedium grandiflorum ‘Orion’
Epimedium grandiflorum ‘Purple Prince’
Epimedium grandiflorum ‘Red Queen’
Epimedium leptorrhizum (spreader)
Epimedium xyoungianum ‘Beni-kujaku’
Epimedium xyoungianum ‘Murasaki-juji’
Epimedium xyoungianum ‘White Star’
Epimedium xyoungianum ‘Yenomoto’