Heucheras are best grown in organically rich, humusy, medium moisture, well-drained soils in part shade. Parentage determines the best culture including optimum sun exposure. Unfortunately, the parentage of many hybrids in commerce today is unknown. Some hybrids will perform well in full sun, particularly in northern climates, but generally prefer some shade in the heat of the afternoon in southern locations. If grown in full sun, consistent moisture is very important. Scorch and general foliage decline may occur if soils are allowed to dry out. On the other hand, some hybrids perform well in shady locations, particularly if H. americana is a parent. Remove stems of faded flowers to encourage additional bloom. Foliage is essentially evergreen in warm winter climates. In cold winter climates such as St. Louis, the amount of retained foliage color in winter depends in large part upon the severity of the temperatures. A winter compost mulch applied after the ground freezes will help prevent root heaving. Divide clumps in spring every 3-4 years. Species plants may be grown from seed, but hybrids are usually divided in the garden.
Heuchera, commonly called coral bells or alumroot, is a genus consisting of about 55 species of evergreen to semi-evergreen herbaceous perennials which are all native to North America. Plants grow in a variety of different habitats including woodland areas, Appalachian seeps, prairies, rocky cliffs and alpine slopes. Plants range in size from dwarf alpine plants with flower spikes rising to only 5” tall to much larger woodland plants with flower spikes towering to 36” tall. Species plants are primarily native to the West, particularly in the Rocky Mountains, with a few species extending into northern Mexico. However, some important species are native to woodland areas in the East and Southeast.
The first significant hybrid heucheras were introduced into commerce around 1980, with the volume of new introductions increasing to almost avalanche proportions in recent years. Hybrids have now supplanted species plants in the marketplace. Species plants most frequently used in producing the hybrids of today are H. sanguinea, H. americana, H. micrantha, H. villosa and H. cylindrica. Leaves of hybrid plants are available in an expanded variety of colors including various shades of green, blue-green, violet, purple, maroon, bronze, silver-black, orange-yellow, yellow, or red, but often with a streaked, mottled or marbled variegation which sometimes includes bold contrasting veins. Flowers of hybrid plants are also available in a variety of different colors including various shades of white, pink, coral or red.
Genus name honors Johann Heinrich von Heucher (1677-1747), physician, botanist and medicinal plant expert at Wittenberg University, Germany.
Common name of coral bells is in reference to the red bell-shaped flowers produced by Heuchera sanguina. Common name of alum root is in reference to the medicinal use of some species plants as an astringent to stop bleeding.
‘Citronelle’ is a vigorous, clump-forming, compact coral bells cultivar that features cordate yellow-green leaves on rosy red petioles. It was discovered as a naturally occurring sport of Heuchera ‘Caramel’ in a nursery bed in Hantay, France in July of 2002. The lobed, crenate, rounded leaves (5-7 lobes per leaf) form a basal mound (to 6” tall) which may spread to 14” wide. Tiny, creamy white flowers appear in spires in summer (later than most heucheras) on slender stems rising above the foliage mound, typically to 10-12” tall. It is the foliage (not the flowers) that distinguishes this plant. ‘Citronelle’ is considered to be more tolerant of hot and humid summers than most other heucheras, in large part because it has H. villosa (SE US native) in its parentage. U. S. Plant Patent PP17,934 was issued August 21, 2007.
No serious insect or disease problems. Frost heaving of roots may occur when winter temperatures fluctuate widely. Potential disease problems include powdery mildew, rust, and bacterial leaf spot. Potential insect problems include weevils and foliar nematodes.
Mass as a ground cover or plant in groups. Rock gardens, borders and open woodland gardens. Effective as an edger along paths or walkways.