Boxwood Blight, A New Menace to the American Landscape
Posted in Gardening Tips on May 14 2013, by Ann Rafalko
Imagine a landscape without boxwood. Some people—who see the shrub as an overused landscape crutch—would welcome it. But what about the home gardener on the hunt for a sturdy, reliable, trusty, deer-resistant shrub to provide their landscape with some backbone? Sure, there are alternatives, but boxwood really can fit the bill in the right design and place. Plus, if you’re a fan of the formal English garden, a world without boxwood is almost unimaginable.
But in the United Kingdom, it’s a real possibility. Home to such famous gardens featuring boxwood as Great Dixter, Sissinghurst, and Helmingham Hall, the gardens across the pond may soon lose one of their most famous plants. Boxwood blight is caused by a fungus known as Cylindrocladium buxicola in the U.K. where it was first found, but is also known as Cylindrocladium pseudonaviculatum or Calonectria pseudonaviculata. The disease was first described in the U.K. in the 1990s, and confirmed in the United States in 2011. It has now been seen in Connecticut, Maryland, Massachusetts, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, and Virginia.
Boxwood blight seems to affect different cultivars to varying degrees, with the most severe infections occurring in the classic English boxwood, Buxus sempervirens ‘Suffruticosa.’ The blight severely disfigures infected plants, first causing dark circles on the leaves and cankers on stems, ultimately leading to leaf drop. In potted box the blight will often only affect the lower branches causing the plant to become misshapen and top-heavy. Large swaths of boxwood, like hedges and topiary, may be affected only on the shadiest or most humid side.
Because of the manner in which boxwood is commonly propagated, young plants are especially vulnerable to boxwood blight. Despite possible total defoliation, the root systems of infected plants remain uninfected. Boxwood blight is not generally the source of plant death. Generally a secondary infection enters the weakened plant and kills it.
Boxwood blight is spread most commonly by transported plants, so much like many state forestry services (including New York’s) will ask you not to transport firewood from place to place in fear of spreading invasive insects like the Emerald Ash Borer, Hemlock wooly Adelgid, and Asian longhorned beetle, it is wise not to transport boxwood. The spores of the fungus can also be spread on tools and clothing, so it is important to maintain all tools and gardening clothing if they have come into contact with infected plants. In addition, should your plants become infected, do not compost them. Take them to your local solid waste depot, bury them, or burn them (though check with local authorities first to ensure there isn’t a burn ban in effect; New York’s lifts tomorrow).
In New York State, if you suspect you have boxwood blight, you can contact the Cornell University Plant Disease Diagnostic Clinic, the Rutgers Plant Diagnostic Laboratory in New Jersey, and the Connecticut Agricultural Experiment Station in Connecticut. And, of course, the Master Gardeners available to the public through the state Cooperative Extension Services are a fantastic resource.
It’s a tough season for gardeners who love both boxwood and impatiens, but a little smart thinking can keep your garden healthy and beautiful. Buy your plants from reputable nurseries, choose the correct plants for your unique gardening conditions, keep your tools clean, maintain vigilance, and keep yourself informed—do all of this, and your garden should remain beautiful well into the fall.
