The National Garden Bureau has selected heuchera as its perennial plant to promote this year. Accordingly, 2012 has been dubbed the "Year of the Heuchera" by that organization. Not only are these plants aesthetically pleasing, they have been improved recently to be stronger, fuller, and more disease resistant. With relatively few pests, great adaptability to containers and a seemingly unending number of forms and leaf colors, heuchera should be in everyone's garden.
The genus Heuchera is a member of the Saxifragaceae family and contains nearly 50 species. Most heuchera (the word is both singular and plural) are native to the United States. Their habitat ranges from the coastal islands of California, to the Rocky mountains, and south to the Gulf of Mexico. The genus was named in honor of Johann Heinrich von Heucher, a German professor of medicine and botany and a friend of Linnaeus, the father of plant taxonomy. Common names include coral bells and alum root. The latter alludes to the medicinal use of certain members of the genus as an astringent to stop wounds from bleeding.
Although a species of heuchera was offered for sale in seed catalogs as early as 1804, for decades it remained a rather utilitarian plant for shady spots that failed to excite the senses. Breeders in America and Europe worked with heuchera to develop a wide array of plants with amazing flower and foliage forms. A milestone was reached in 1980 when Heuchera villosa 'Palace Purple' was released. At about the same time, a strain of Heuchera americana called 'Dale's Strain' was released. Heuchera soon was accepted by gardeners as a desirable foliage plant for shady areas and its popularity continues to grow.
As previously stated, there are nearly 50 species of heuchera inhabiting various regions of the United States. The flowers of most are dainty with a color range of whites, pinks and reds. There are a few cultivars with flowers that have a very pale yellow tone. Although the flowers of some cultivars are quite showy, heuchera are grown primarily for their foliage. The latter can vary in size from the ½" wide leaves of H. pulchella to the 11" wide leaves of H. villosa. Foliage can be matte or glossy, hairy or smooth, and can have contrasting veins which change color with the seasons.
Before the new wave of hybrid heuchera, many claimed a heritage that included only one species, H. sanguinea. This species is the coral bells your grandmother grew. Today, however, in order to give gardeners stronger, more attractive plants, breeders are combining species so the newest coral bells provide a mix of outstanding characteristics. The common species used in today's hybrids are H. sanguinea, H. americana, H. micrantha, H. villosa, and H cylindrica. 'Chocolate Ruffles', for example is hybrid between H. micrantha and H. americana and 'Velvet Night' is a hybrid between H. micrantha and H. americana. The very colorful, striking variety 'Electra,' reportedly is a mix of three species: H. americana, H. micrantha, and H. villosa.
By taking Heuchera, with its many forms and leaf colors and crossing it to Tiarella (another genus in the Saxifragaceae family), whose beauty is defined by leaf-shape, zonation and growth, a vast array of new hybrids referred to as "Heucherella" have resulted. They tend to exhibit the best qualities of both of their parents, having brightly-colored foliage with dark leaf patterns with unique shapes. Their culture is similar to that of heuchera.
When using heuchera in the landscape, they are best triangulated with most cultivars planted 24 inches on center. Look at the plant label to determine the spread and best spacing. Heuchera require well-drained soil. If you've had problems with them in the past, most likely you've tried to plant them in soil that's too wet or "heavy". Incorporation of organic matter such as compost into the soil will help lighten it and improve drainage. Additionally, planting in raised beds, on berms or in containers can help to solve drainage problems.
Other than keeping the soil well-drained and mulched, heuchera have very few maintenance needs. Allow them to dry between watering and refrain from using excess fertilizer. Heurchra prefer a neutral or slightly acidic soil (the ideal pH is 5.8 to 6.3) but most are tolerant. Most varieties are drought-tolerant as well.
Many heuchera do well in part-sun exposures, however, hot afternoon sun should be avoided. Foliage will often fade, wilt, or scorch under intense sunlight. Instead, provide shade during the hottest times of the day, or plant heuchera in full or filtered shade.
Heuchera are remarkable for needing little care. When flowers fade, they can be removed with little effort. If stems get too long they can be cut off; the resulting stub will re-sprout and the piece that was removed can be replanted to form a new plant. This helps keep heuchera compact. It's best to divide them every two to three years, with the spring being the best time to perform this task.
While many heuchera are initially propagated by tissue-culture, they can be divided by a sharp shovel in early spring when the soil has thawed. A two-year-old plant can easily be divided into as many as six plants. Place the divisions buried to the crown in a good garden soil and water in. Foliage may have to be removed if any wilting is observed.
Heuchera have relatively few pests but they do suffer from attack by strawberry or black vine weevil. Plants whose tops "fall off" in the spring most likely were being eaten underground by weevil larvae. These are creamy-white grubs somewhat crescent-shaped. Weevil control involves a twofold approach. The brown or black adults emerge in late May to early June and can be treated with an insecticide that has some residual activity such as acephate. In fall, beneficial nematodes can be applied to the soil around the plants to help control weevil larvae.
There are two diseases especially troublesome for heuchera: mildew and rust. Mildew tends only to attack varieties of Heuchera sanguinea. Organic controls such as baking soda in water can provide some prevention. Mancozeb can be applied as both a preventative and a remedy. Rust can be a severe problem if the plants are moist and the temperature is cool. Infected plants will appear dark-spotted from above and, when a leaf is turned over, orange patches are evident. Preventative measures for rust include clean, dry facilities (for growers) and fungicide application. Mancozeb, thiophanate-methyl or chlorothalonil can prevent rust infestation and provide long-term control. Once a plant has been attacked, remove the affected leaves and apply one of the above sprays. Clean and disinfect equipment after use.
Credit: This article was adapted from a publication of the National Garden Bureau.
REVISED: July 2, 2012