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×Heucherella ‘Quicksilver’ in
the Dry Shade Garden by
Martha H. Oliver
(Charles Oliver of Primrose Path, Scottdale, Pa, is the breeder of ‘Quicksilver’) Gardeners are frequently baffled by the soils under trees, especially those under beech, apples or maples; these shallow-rooted trees seem to extract all the moisture and nutrients from their area, leaving little or nothing for perennials struggling to grow under their branches. But the trees themselves are so wonderful, offering shade, privacy, and noise reduction, that removing them is out of the question. Before you give up and plug in Ivy, Vinca or Pachysandra, however, visualize the shade garden that could grow there, using a group of plants specially suited to the seasonally moist but mostly dry conditions found under deciduous trees. Central to the planting is a new perennial ×Heucherella called ‘Quicksilver,’ a bi-generic hybrid between two plants: Coral Bells (Heuchera) and Foam Flower (Tiarella). The reason ‘Quicksilver’ succeeds where others fail is its vigor and endurance, which it gets from two of its parents: the Coral Bells of the West Virginia shale barrens (Heuchera pubescens) and the Foam Flower of the eastern woodlands (Tiarella wherryi). ‘Quicksilver’ has the added delight of being one of the loveliest plants to be introduced into cultivation in many decades. With silvery, metallic leaves that reverse to a rich, red-purple, ‘Quicksilver’ sends up many spikes of soft pink buds which open to starry white flowers in May and June. The leaves are evergreen, so they are present all through the winter. Under the winter sun, they turn a dark mahogany red, and the new spring leaves emerge with a purple cast as they unfold with their characteristic silver overlay. Other ×Heucherellas have been introduced recently, but they have other Heucheras as one parent, usually Heuchera brizoides, and these just don’t have the drought tolerance from the shale barrens parent. H. americana is part of ‘Quicksilver’s’ ancestry too and the toughness it brings can’t be outdone by any other plant on the market.
Some Eastern U.S. native woodland plants that make good companions are Stylophorum diphyllum, the Golden Wood Poppy, and Mertensia virginica, the Virginia Bluebells, for April flowers; Dryopteris felix-mas and Dryopteris marginalis, our Male Fern and Marginal Shield Fern, for summer foliage; and Eupatorium rugosum ‘Chocolate’, the lovely purple-leaved white Snakeroot, for flowers in October. The early leaves of this native are dark purple like those of ‘Quicksilver.’ I would also add Cyclamen hederifolium, the hardy Cyclamen, for small pink flowers in the autumn; Epimedium xversicolor ‘Sulphureum’ for yellow flowers in May; and Fritillaria meleagris, the Guinea-flower, for its mahogany hanging bells in spring. I would also put in some Lords and Ladies, Arum italicum pictum, for the lovely variegated foliage from October through the cold winter until it sends up its hooded pale green flowers in spring, always willing to share the space with Hostas (which produce leaves as the Arums are dying down for the summer). These aren’t native plants, but they have interesting leaves, and pay their way in the dry shade garden. A group of plants I saw in a friend’s garden under a Norway maple made me see the loveliness of these tough plants. It was late April, and she had planted Symphytum grandiflorum, with pale yellow hanging bells, Epimedium ‘Frohnleiten’ with soft yellow flared flowers, and Tulip batalinii ‘Bright Gem,’ with small species Tulip blooms in the same soft yellow. She had ‘Quicksilver’ near this group and the beauty of this early spring mix of soft yellow flowers, purple ‘Quicksilver’ leaves and the blue foliage of the Tulips was breathtaking. Another evergreen companion for ‘Quicksilver’ is Helleborus foetidus, whose narrow palmate leaves seem to glisten with a dark metallic sheen. The green flowers in January and February are interesting rather than beautiful, but they are welcome because of their earliness and hardiness. I also like to see the small grey-blue leaves of Sedum ternatum and S. nevii, both native to eastern U.S., and their starry white flowers in spring. Hardy Geraniums, such as G. macrorrhizum, G. phaeum, and G. endressii ‘Claridge Druce,’ share a willingness to bloom and thrive in dry shade, as does Liriope, the narrow leaved Lilyturf, which blooms in the late summer and fall. These, and all the plants mentioned in this article, enjoy a soil pH that is near neutral, which is also the soil preference of ‘Quicksilver.’ Don’t try to plant these in very acid soils, the types that suit Rhododendrons, Azaleas, Heathers and Blueberries.
Planting Tips Of course, establishing these plants in their challenging new home will be more successful with some soil preparation first. If the ground is absolutely undiggable, as is often the case under maples, it is easy to spread mulch to a depth of six inches, and, if it is very acidic, to add a bit of ground limestone. Just be sure to keep the mulch at least a foot away from the trunk of the tree to avoid suffocating the roots. Of course, aged mulch is greatly to be preferred to fresh, but unless you can order a truckload and allow it to rot, this will be hard to find. If the weather is dry, some water is necessary to establish the plants. You can use the rule that plants need an inch of water a week for the first three or four weeks. A small gauge or a straight-sided can will let you know how much water has fallen. After the plants are well rooted in, they should not need more water unless the summer is very hot and dry (as has been the case recently!). All of these plants will return each year, slowly increasing in size, blooming in their season but offering foliage textures, which change as they sprout, unfold, mature and wither. The shade garden, which uses the leaves of the plants as a focal point offers more to the gardener than one that is utterly dependent on flowers. Hostas are grown for their leaves rather than their flowers. What if there was a perennial, which had wonderful leaves, but had them all year? What if this plant also boasted lovely flowers for eight or ten weeks? Suppose this plant was unattractive to slugs and deer as well? And when the frosts of fall cut down the Hosta leaves, this plant just kept on going? This plant is ×Heucherella ‘Quicksilver.’ It is available from Blooms of Bressingham North America and from garden centers across the country. It won first prize at the Royal Society for Horticulture perennial plant exposition in Lisse, Holland, in September 1997. It was bred by Charles Oliver of The Primrose Path. It is destined to become one of the classic garden plants of all time. Shouldn’t it be in your garden?
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