Institute Feature

The UT Experiment Station's newest dogwood cultivar 'Appalachian Joy' features blossoms with more than four bracts. Download this photo (359 KB)

Will they be spectacular this year? It’s the million-dollar question posed by those anticipating the annual display of one of nature’s finest flowering trees, the dogwood.

Known the world over for its full, cascading display of white, pink, or red blossoms, flowering dogwood is experiencing a popular resurgence after sales declined due to the chronic presence of two diseases that destroy the trees – powdery mildew and dogwood anthracnose. Researchers with the Tennessee Agricultural Experiment Station helped drive the new interest by developing cultivars that are resistant to these diseases.

“During the early 1990s, dogwoods comprised more than 20 percent of nursery sales, “ says Mark Halcomb, a nursery production specialist with University of Tennessee Extension, “but when an epidemic of powdery mildew affected almost all flowering dogwoods in 1994 and 1995, sales plummeted.”

Powdery mildew and dogwood anthracnose attack foliage, stunt growth, and can result in early mortality. Infected trees require frequent treatments with expensive fungicide sprays. When the diseases hit, nurseries were burdened with elevated production costs, and the higher cost of ownership and required maintenance of infected trees detracted from the dogwood’s popularity with homeowners.

A drop in consumer interest translated into trouble for the state’s economically important nursery industry. Tennessee ranks third in the nation with more than $27 million in annual sales of flowering deciduous trees (including dogwoods), and Warren County bills itself as the world’s nursery capital. Roughly 650 plant nurseries are scattered throughout the county.

Researchers with the Experiment Station addressed the problems by developing several patented cultivars of dogwoods that are naturally disease resistant. Named for the researcher’s wives and mothers, ’Kay’s Appalachian Mist,’ ’Jean’s Appalachian Snow,’ and ‘Karen’s Appalachian Blush’ are the only white-bracted cultivars known to be highly resistant to powdery mildew.

Another UT cultivar, ‘Appalachian Spring,’ has proven resistant to dogwood anthracnose, but not to powdery mildew. Appalachian Spring is now available through retail suppliers, and the other cultivars may be available as early as next spring.

“Meanwhile, the dogwood breeding team continues to pursue the holy grail of flowering dogwood – a tree that has resistance to both diseases,” says Mark Windham, a professor of plant pathology and member of the UT Dogwood Research Group. “Efforts have been underway for the last eight years to combine resistance to both diseases into one cultivar.”

The team’s newest cultivar, ‘Appalachian Joy’ (patent pending), is also highly resistant to powdery mildew; however, disease resistance may not be its most marketable trait. The new cultivar’s blossoms have extra bracts. ”Anywhere from four to seven bracts appear on different branches on the same tree,” says Bob Trigiano, also a professor of plant pathology and member of the research team.

“Since normal dogwood blossoms feature only four bracts, the increase in bracts makes for a more spectacular display,” Trigiano adds.

Developing these new cultivars should be a boon to the state’s nursery industry. A study by UT Extension and Experiment Station researchers maintains that promoting disease-resistant trees in Tennessee creates an estimated $7.8 million in additional revenues for nursery producers.

Of course, the beauty of the blossoms helps sell trees, too.

— Carolyn Corley

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Contact:

Patricia McDaniels, UTIA Marketing and Communications
(865) 974-7141 or pclark@utk.edu

Many flowering dogwood cultivars are on public display at the UT Arboretum in Oak Ridge. For more information, see http://forestry.tennessee.edu/arbpage.htm