Native heucheras, also called alumroot or coral bells, have always been high on my list of favorite perennials. I know the ones grown for flowers well from my years in California. Then I moved East and discovered the numerous new hybrids grown primarily for their bold, showy foliage. Here's what I've recently learned about this increasingly popular genus.
There are approximately 50 species in the genus Heuchera. All are natives of North America and Mexico. Natural habitats range from rocky cliff faces on California's coastal islands, where you'll find H. maxima, to seeps of North Carolina's Great Smoky Mountains, home of H. americana. Few of the species are grown as ornamental perennials. But there are now many hybrids and selections of them.
Because Heuchera species come from different climates and habitats, there are many regional distinctions. In the West, coral-flowered H. sanguinea is native to Arizona, New Mexico and Mexico and is very successful and popular in gardens there. It won't tolerate the extreme heat and humidity in the Southeast, however. In that region, two of the best are H. villosa var. macrorhiza (pale green leaves and late-blooming tiny white flowers) an, the rock geranium (green mottled with white leaves and greenish white to purplish flowers).
Beyond guesswork and experimentation based on hybrid parents' native ranges, it's hard to know exactly where different heucheras will grow well. Most garden varieties have not been tested nationally. According to Horticulture Director Bart O'Brien at Rancho Santa Ana Botanic Garden, Claremont, California, "People are experimenting with heucheras now more than ever, seeing what's available and learning what grows best for them."
There are regions where several kinds of heuchera grow well and are widely appreciated. In Oregon and Colorado, for instance, both foliage types (Heuchera americana) hybrids and showy flowering types (H. sanguinea) hybrids flourish side by side.In other regions, either flowering or foliage types predominate.
In California gardens, showy flowering types are best known. Gardeners there are excited by new crosses between Heuchera sanguinea and California natives such as H. maxima and H. rubescens. These produce bright pink and red blossoms.
In the Pacific Northwest, the Midwest and much of the East, foliage varieties have taken gardeners by storm. "They are hot and trendy in this area," says Rick Darke, curator of plants at Longwood Gardens in Pennsylvania. He especially values their year-round beauty and uses them extensively as ground covers.
One reason for the growing popularity of heucheras is their stunning array of leaf colors, shapes, sizes and textures. Those with showy foliage (often called alumroot) are striking as small-scale ground covers, in perennial borders and in containers. The leaves are also attractive in floral arrangements. These foliage heucheras are evergreen in all but the most severe climates. Foliage does deteriorate as winter progresses, however. Still, these rank high for adding color highlights through much, if not all of the year.
Top varieties to look for include the following:
Heuchera 'Palace Purple' (also called H. micrantha diversifolia 'Palace Purple') was the first to be widely grown for its dramatic foliage. It was introduced to American gardens in 1986 and remains popular for the way its rich purple maple-leaf foliage contrasts beautifully with greens and golds.
Heuchera americana 'Garnet' is notable for leaf color that changes with the seasons from garnet tones to dark green marked with deep wine red.
H. americana 'Dale's Strain' is a variable seed-propagated variety with silver blue marbled foliage.
Recent introductions of foliage heucheras from Oregon nurseryman and plant breeder Dan Heims are making a big splash. Some of the top picks among the many he offers are listed here (all are hardy in USDA zones 4 through 9).
H. americana 'Pewter Veil' has pewter purple leaves with charcoal gray veining. The entire 20-inch-wide mound of foliage has a metallic sheen. Individual leaves grow 6 inches or more across. It combines beautifully with Japanese painted fern (Athyrium nipponicum 'Pictum')," raves horticulturist Kelly Grummons of Paulino's Gardens in Denver. It complements the purple, lavender and silvery greenish gray of the fern's leaflets.
H. 'Chocolate Ruffles' has ruffled leaves to 9 inches wide. They are chocolate colored on top and burgundy below. The burgundy peeks through the ruffles, giving a two-tone effect. The mounding plant, topped with thousands of tiny white flowers on purple spikes, spreads slowly to about 20 inches wide.
H. micrantha 'Ruffles' forms a 30-inch-wide mound of incredibly ruffled woolly green leaves. Flowers are small and white.
H. sanguinea 'Splish-Splash' is one with showy foliage and bright, showy rose flowers. The variegated 3-inch-wide leaves are marbled white over green with pink veins. The plant grows to 18 inches wide.
Heucheras with airy clusters of tiny bell-shaped flowers (usually called coral bells) are much cherished as cut flowers. And hummingbirds love them, too! Most start blooming in May or June and continue into July or August. They brighten woodland gardens and perennial beds, and are useful container plants. For a shower of heavenly blossoms, plant groups of the same variety together.
Neighborhood nurseries specializing in perennials may be the best indicators of which of the dozens of varieties will perform well in your area.
Heuchera brizoides (hybrids of H. sanguinea, H. micrantha, and perhaps H. americana). There are many named varieties in a range of flower colors. Some to look for include deep rose 'Chatterbox', cardinal red 'Mt. St. Helens', pure white 'June Bride' and in mixed colors, 'Bressingham Hybrids'. In flower, plants reach approximately 18 inches.
Among the outstanding choices for western gardeners are hybrids developed by the late Dara Emery at Santa Barbara Botanic Garden. These include Heuchera 'Canyon Pink' (bright pink flowers with light centers) and H. 'Canyon Delight' (rose pink flowers).
There are several excellent introductions of Heuchera sanguinea and H. maxima hybrids from Bart O'Brien at Rancho Santa Ana Botanic Garden. One is 'Genevieve' with deep pink, white-centered blossoms on stems to two feet. The attractive two- to three-inch leaves are green mottled with gray. Others most readily available in California are H. 'Santa Ana Cardinal' (red flowers) and H. 'Susanna' (pink flowers).
Generally available at retail nurseries and botanic gardens, the California heucheras are still hard to find outside the West, and are not generally available through mail-order catalogs.
Depending on where you live and the varieties you grow, planting and maintenance needs vary. Generally, heucheras grow best in reasonably well-drained soils that are rich in organic matter. In northern gardens and mild coastal areas, some can handle full sun. More often, heucheras look best grown in partial shade. To help prevent mildew, space plants to allow good air circulation between them. Once established, heucheras require moderate to little watering.
Heucheras usually need dividing every four or five years, though some need it when younger and others can look great even at nine years without dividing. When the stem becomes woody, the plant falls open at the center or flowering is reduced, it is time to divide. The best time is in spring just before growth begins in earnest.
One of the few insect pests of heuchera is the small beetle known as the strawberry root weevil. The larvae feed underground on plant roots. Extensive feeding will eventually cause the plant's crown to die and break off at the soil level. One nontoxic control for the weevil larvae is parasitic nematodes. Mealybugs may also be a problem. Treat infested plants with insecticidal soap. Consult your local nurseryman for more information about these pests and their management.
Photography by Suzanne DeJohn/National Gardening Association
Article published on June 23, 2008.