The arching stems, decorative berries, and warmly hued, persistent fall foliage of barberry, plus the complete lack of deer browse on their twigs, are why they were brought to the U.S. as an ornamental plant in 1875. That was fine, until in the 1980s they started to spread out and displace native plants. Now Japanese barberry is considered invasive in 17 states, including Wisconsin, Minnesota, and Iowa.

A barberry thicket also provides a safe, fox-resistant haven for mice, and a shady, humid home for ticks. Deer ticks feed on mice, who are reservoirs for Lyme disease.