Native to eastern Asia, Japanese barberry (Berberis thunbergii) was introduced in 1875 in the United States as a popular ornamental shrub for making hedges and filling building foundation beds. The purple-leaf barberry Berneris atropurpurea increased the landscape appeal with its burgundy foliage that turns red and orange in autumn. The thorny branches bear small yellow flowers in mid-spring that yield to abundant production seeds that sprout up all over after being eaten by game birds and small mammals.
Japanese barberry wins favor as a garden plant because of its broad list of tolerances that allow it to prosper in locations where other ornamental plants falter. This species grows in both full sun and in partially shaded locations in alkaline and acidic soils. The plant's tolerance for high summer heat, winter cold and seasonal drought sets it up to be a low maintenance plant.
The problem with Japanese barberry centers around the copious production of seeds each summer that readily sprout to produce thickets. Suckers, or sprouting shoots, also may arise from roots at the surface of fertile garden soils. This shrub species is a noxious weed or invasive plant prohibited for use in Canada and at least 20 U.S. states. According to the Plant Conservation Alliance, this shrub creates dense stands in natural North American habitats including canopy forests, open woodlands, wetlands, pastures, and meadows and raises soil pH, lowers nitrogen levels and biological activity in soil. Deer avoid eating barberry's thorny branches and thus focus on eating away at native shrubs instead.
A very labor-intensive solution to controlling this barberry is the manual removal or mechanical weakening of plants. Digging out shrubs less than 3 feet in height or repeated severe pruning of shrubs robs the roots of food and eventually kills them. Be aware, though, that root remnants left in soil tend to resprout new plants. Pruning, chopping off or mowing away shrubs before the seeds ripen prevents wildlife from eaten them and dispersing them into new landscape areas.
Large infestations of Japanese barberry that cannot be efficiently eradicated by physical means are best treated with herbicides. Two chemicals demonstrate effectiveness: glyphosate and triclopyr. Both, unfortunately, are non-selective herbicides, meaning they will kill any plant they contact. Spray these chemicals cautiously, making sure the residue saturates barberry foliage and no nearby desirable ornamental or native plants.
Unfortunately, the Plant Conservation Alliance reports that there is no effective biological control for Japanese barberry. Trials on various insects, fungi and other natural organisms fail to reveal an effective, economical, natural way to kill the plants.
While many ornamental varieties of Japanese barberries continue to be sold at garden centers across North America, an effort to educate nurserymen and the gardening public can reduce the demand for these fast-growing and inexpensive landscape shrubs. Some jurisdictions restrict sale of the shrubs, while other efforts to offer non-invasive, comparable shrub alternatives to consumers can help limit the continued spread of barberry and need for time-consuming and costly removal of the shrubs from native ecosystems.