The plant genus x Heucherella is a human-created genus. Botanists accredit it to Alan Bloom, an English plant breeder who crossed plants from the genus Heuchera, or coralbells, with plants from the genus Tiarella, or foamflowers. The resulting plant hybrids generally are small, evergreen plants that gardeners select for their colorful foliage and bloom stalks. Generally, various cultivars vary in hardiness and color sustainability; therefore, gardeners need to research the plants before purchasing them.
Technically, the name is xHeucherella or x Heucherella. Generally, in botanical writings, experts universally use the x to denote that a plant is a hybrid. The x before the plant name denotes that the plant results from a cross between plants from two different genera. In this case, both Heuchera and Tiarella belong to the Saxifrage family. Often people eliminate the x, especially non-plant writers or copy editors; both spellings are acceptable.
Generally, gardeners grow the x Heucherella plants for their boldly veined leaves. Typically, the leaves have seven to nine lobes around the edges of heart-shaped or ovate leaves. Depending on the hybrid, the leaf color varies widely from light colors like yellow to deeper greens, and some have a frosty appearance, such as the cultivar pink frost foliage. The markings usually follow the vein lines and may range from darker greens to bronze to red, especially maroons. On average, the foliage is only about 10 inches (25 cm) tall and wide.
The flowers of x Heucherella plants typically ascend high above the foliage on leafless stalks that may measure up to 18 inches (about 45 cm) tall. The stiff stalks usually are maroon, brown, or reddish brown, and the buds often match the stalk color. Generally, the flowers are small, bell-shaped, and pink or white and may bloom all summer, depending on the cultivar. Most of the flowers are about one quarter of an inch (6 mm) in diameter or smaller. They are borne in short, loose panicles — branched stalks with the youngest flowers at the tip.
Depending on the cultivar, x Heucherella plants may not be hardy in areas of hard frost. Usually they thrive in regions that have temperate climates where there are distinct seasons, but not extreme temperatures. Most of the cultivars do not survive in areas where there is not a cool or cold winter. Although they usually tend to prefer partial shade, some cultivars do well in sunny areas.
One of the popular cultivars, H. tiarelloides, has larger leaves than many x Heucherella plants. They may measure more than 3 inches (about 7 cm) long, whereas many cultivar leaves are between 1.5 and 3 inches (4 and 7 cm) long. Sometimes hybrid plants with light-colored or yellow leaves tend to lose their special foliage color, and the color reverts to plain green. Landscapers usually research a hybrid's performance history before planting it.
Growers plant x Heucherella hybrids as ground covers and edging plants and as specimen plants. They are one of the few plants that often thrive in woodland gardens. Sometimes gardeners use it as a container plant. Growers propagate the plants through division of the stolons.