Chicago Botanic Garden Evaluates Coral Bells

The Chicago Botanic Garden has released results of a six-year comparative study of coral bells, or Heuchera, in the 21st issue of the Chicago Botanic Garden’s “Plant Evaluation Notes: An Evaluation Study of Coral Bells.”

Coral bells are herbaceous, evergreen perennials with generally spreading habits. An astounding number of cultivars have been introduced since the early 1990’s, with exciting developments in foliage colors-purple, ruby, bronze and amber, as well as patterns with prominent or colorful veins, mottling and streaks. The bell shaped flowers come in shades of red, pink, coral and pure to greenish white. The small delicate blossoms appear in late spring clustered on wiry stems above the foliage.

Coral bells grow best in light shade and moist, well-drained organic soils. They will grow in full sun if the soil is consistently moist, but good drainage is essential to good health. Although coral bells are disease- and pest-resistant, crown rot may be a problem if soils do not drain adequately during winter.

Coral bells are used as accents or in groups in perennial borders, rock gardens and woodland gardens. They can be grown with other foliage plants that contrast or complement their leaf color; for example, Japanese painted ferns or spotted dead nettles are good companions with purple-leaved cultivars. They mix well with tulips and daffodils as well as hostas, ferns and other woodland perennials.

The Chicago Botanic Garden (USDA Hardiness Zone 5b, AHS Plant Heat-Zone 5) evaluated more that 60 species and cultivars of Heuchera from 1995 to 2000. The goals of the trial were to observe many of the new Heuchera cultivars that were commercially available at that time to determine the best coral bells for Midwestern gardens.

Each of the 64 taxa planted in spring of 1995 were observed through autumn of 2000 for winter injury, cultural adaptability to the soils and conditions of the test site, disease and pest problems, and ornamental traits including foliage and habit quality, plant size and floral display. The 43 taxa that completed all five years of the study are compared in a chart of characteristic and performance in the Plant Evaluation Notes. The remaining 21 taxa lived for two years or less and were not retested.

Significant problems included periodic rabbit damage in early spring, leaf spot and stem rot. Crown heaving due to age or frost is a common problem on coral bells, however, few plants were adversely affected by heaving or required division or replanting. Winter hardiness was not considered a problem for the coral bells in the trial.

The top-rated coral bells in the Garden’s trial were ‘Bressingham Bronze’, ‘Cappuccino’, ‘Molly Bush’, ‘Montrose Ruby’, ‘Palace Purple’ and Heuchera sanguinea ‘White Cloud’. Each of these coral bells received the highest marks based on good habit, healthy foliage, high flower production and winter hardiness. Heuchera ‘Molly Bush’ was the highest rated, with dark purple foliage and greenish white flowers from mid-July though early October and 80 percent flower coverage. Heuchera sanguinea ‘White Cloud’ was also highly rated, with light green foliage with silver flecks and white flowers from early June through late July and 80 percent flower coverage.

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