Oh, deer. Every Adirondack gardener has had a run in with this long-legged herbivore snacking on our annuals and perennials, otherwise known as ephemerals when they are deer approved. Many gardeners likely have repeatedly searched the Internet for deer-resistant plants and deer repellents and quizzed fellow gardeners and nurseries about which plants have the highest likelihood of survival. I am one of those gardeners. Now I nurture a mostly toxic, noxious and inedible garden, but even this is not foolproof.
Sometimes at garden centers or talking with homeowners, I hear their recommendations for one of the only tried and true deer resistant plants: Japanese barberry (Berberis thunbergii). This decorative, woody shrub has sharp pines, making it one that the deer avoid and thus one that is desirable to gardeners and landscapers. Unfortunately, this unpalatable ornamental comes at a price.
Japanese barberry is one of the most popular landscaping plants, but it doesn't stay put. It spreads beyond our plantings, often assisted by birds or small animals, and invades our forests and, I'm told, even shorelines. I see baby barberries growing in my woods, springing up under their mother plants in ornamental hedgerows in town and maturing into dense thickets in forests. Infestations are well established in natural areas elsewhere in the state, and numbers are on the rise in the Adirondacks, particularly in the Champlain Valley, Old Forge and other communities around the periphery of the Park.
Japanese barberry is a popular ornamental that can invade forests and harbor deer tick populations.
(Photo — Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)
Japanese barberry poses risks not only to the environment but also to human health. Besides crowding out native forest vegetation, degrading food and habitat available for wildlife and preventing tree seedling regeneration, dense infestations of barberry are now linked to increased outbreaks of Lyme disease. Scientists from the Connecticut Agricultural Experiment Station investigated the relationship between Japanese barberry, ticks that carry Lyme disease and deer overpopulation.
Deer don't browse thorny barberry plants; deer preferentially feed on natives and drive those plant populations down, decreasing their ability to compete and increasing the likelihood of barberry survival and expansion. When barberry thickets form, they create a cool, moist microclimate that is favored by ticks.
The research conducted in Lyme, Conn. - the location of the first case of Lyme disease in the 1970s - shows that deer ticks are 67 percent more likely to be in areas infested with barberry than those areas that have native plants, and a higher percentage of ticks in infested areas carry the Lyme bacteria than those in areas that are barberry-free - 126 infected ticks per acre versus 10 per acre. When managers removed barberry plants, the number of ticks dropped up to 80 percent - a compelling outcome.
Communities and homeowners can help stop the spread of Japanese barberry. Since barberry is such a popular ornamental, particularly in areas where deer populations are high, the best place to focus on removing plants is in areas where they were not intentionally planted, such as in forests, along river corridors and along shorelines.
Treatments should occur prior to when seeds are set in the fall. Medium-sized to small plants are easier to uproot with a pitchfork or hand pull in the spring or after rains when the soil is loose. Make sure to remove all of the roots. Plants can be left root-side-up to dry out and then disposed of in the trash or burned. Larger plants can be cut, and then an approved herbicide can be applied to the cut stumps. Using a propane torch can also be effective, but be sure to learn the proper technique. Find out more about this control method at www.ctforestry.uconn.edu/JapaneseBarberryControl.html.
Japanese barberry is still available for sale in New York; however, a new law instituted this summer will regulate the sale of invasive species in the state and will clamp down on the availability of the worst invasives. In the meantime, landowners, landscape designers and nursery owners can help by considering replacing Japanese barberry with alternative ornamentals such as winterberry, ninebark and bayberry.
For more information about starting a local invasive plant control project, or for information about alternative choices to invasive ornamentals, contact the Adirondack Park Invasive Plant Program at 518-576-2082.