Plant profile: epimediums
New introductions in epimediums are increasing their popularity as well as reinvigorating enthusiasm for the more established cultivars
With pretty spring flowers and interesting foliage these woodland plants are a useful addition to a shady corner
Every year at Chelsea there seems to be some must-have plant to beguile us – the latest bearded iris; the newest geranium – making its debut to a fanfare of praise. But only very occasionally do new species emerge. Yet, somehow, over the past ten to 20 years a deluge of new epimediums have slipped into commerce almost unannounced. They’re being introduced by western plant hunters who are, exploring the remote valleys of the Sichuan and Yunnan provinces of China. The resulting plants are dramatic with larger flowers in different forms and myriad colours: a world away from the epimediums that traditionally fill those difficult spaces in dry shade. Their introduction has inspired garden designers to try out and use not only some of these new forms, but to re-assess those old, useful plants whose delicate spring flowers hover above and below bronze, evergreen foliage that few weeds can penetrate.
In the early 19th century the German botanist Philipp Franz von Siebold sent some of the epimediums he had collected while living in Japan to the Hortus Botanicus at Leiden and the Ghent University Botanical Garden, which today holds the reference collection for all epimediums. Modern breeders have developed these acid-loving Japanese species to produce new forms with larger f lowers. The delicate, bell-shaped flowers are predominantly pink, purple or white, although Epimedium grandiflorum ‘Yellow Princess’ has lemon and white f lowers: an exception that proves the rule.
Epimedium grandiflorum crossed with E. diphyllum, produces the hybrid E. x youngianum. These exquisite f lowers look like little silk tassels with few, if any, spurs, and they too are acid lovers. Plants such as E. x youngianum ‘Niveum’ have entirely white f lowers like snowf lakes, on wiry red stems, and those of E. x youngianum ‘Tamabotan’ have tousled, double, pink f lowers. They, too, are herbaceous, but the leaves often flush red in autumn before dying away.
Gardeners on alkaline soils have found that the Japanese species grow very well in pots of ericaceous compost, in a shady corner of the terrace. They only need to be tipped out and divided every few years, and friends are made with gifts of the surplus plants.
However, it’s the new Chinese species and their hybrids that are currently wowing the horticultural world. Twenty years ago the late William Stearn began systematically to rationalise the entire genus, and although, he found many anomalies, his work resulted in naming 54 species. There have been very many more additions since, not least from the great Japanese plant collector, Mikinori Ogisu, and American planthunter Darrell Probst. Probst has also bred some spectacular crosses, including ‘Pink Champagne’ (right), with wide, pink sepals over deeper pink centres like hang-gliding spiders over a mat of dark, mottled foliage.
In this country, many of the new species were distributed through plantsman Roy Lancaster to a handful of British growers, including Robin White of the former Blackthorn Nursery. His crosses resulted in glorious plants, such as the marmalade-coloured E. ‘Amber Queen’ and E. ‘Pink Elf’ whose swarms of two-tone pink flowers often repeat throughout the summer. In the Netherlands and Belgium, a number of enthusiastic nurserymen are developing startling new hybrids, such as Koen Van Poucke’s E. ‘Red Maximum’. They are all selecting for large flowers that are held well above their gorgeously marked young leaves, and are also developing new colours: soft apricot and lavender, browns and reds, and two-toned flowers. In the UK nurserymen are crossing the large-flowered Chinese hybrids with the spreading forms. All are working on making these exciting new plants available to an appreciative gardening world. • Author Sally Gregson is the owner of Mill Cottage Plants in Somerset, and the author of The Plant Lover’s Guide to Epimediums ( Timber Press, 2015). Her recommendations for the best epimediums can be found over the next five pages.
Cultivation
Epimediums are happiest in well-cultivated soils that hold some moisture but are well-drained. They appreciate a mulch of leaf mould in winter. All prefer light shade, preferably from overhead, but that provided later in summer by hydrangeas, roses and other deciduous shrubs is excellent. Most traditional types grow happily in dry soil under trees, but let them loose in the rest of a shady garden and you risk a bid for world domination.
The Japanese species – E. grandiflorum, E. sempervirens, E. x youngianum – prefer a rich, acid soil, and effectively fill in the gaps between rhododendrons and camellias. The new, evergreen Chinese species and their hybrids are happy in both acid and alkaline soils but prefer a rich, free-draining soil in shade, and steadily make bigger clumps without becoming invasive. The familiar, groundcovering forms should be trimmed over with shears in February before the flowering stalks extend. The over-wintered leaves of the Chinese species and hybrids can be cut back with more restraint in spring.
All epimediums are self-sterile, which means that any seed that forms is the result of hybridisation with its neighbours. It’s important to cut off the seedpods to prevent seedlings arising in the crown of the mother plant. Lift and divide the mature plants after they have finished flowering during cool, damp weather. Replant them where they are to flower in ground that has been well prepared, preferably with leaf mould.
Epimediums are relatively disease-free, although they are prone to damage by vine weevils and at the first signs you should apply nematodes. Plants with thick, malformed or spotted leaves, or those with a yellow or cream mosaic pattern, may have tobacco rattle virus, which is transmitted through soil-living nematodes – although not those used to control vine weevils. If you spot any signs you'll need carefully to dig up the infected plant, and the plants around it, and dispose of all plants completely in a plastic bag. Don’t replant epimediums in that space for at least five years. In country gardens it may also be worthwhile installing rabbit-proof fencing around the planted area as rabbits find epimedium leaves delicious.