Japanese barberry (Berberis thunbergii) is a perennial deciduous shrub native to Japan, now considered a serious invasive in the United States. This attractive plant was sent to Arnold Arboretum in 1875 as a suggested ornamental, and became a common cultivar for settlers in New England. When the European barberry (Berberis vulgaris) was later found to host black stem grain rust (Puccinia graminis f. sp. tritici), a destructive wheat and grain fungus, a long federal and state eradiation campaign to control B. vulgaris began in 1918 and the USDA encouraged planting of the closely related Japanese barberry as a fungus-resistant and attractive substitute (USDA Agricultural Resource Service 2010; Swearingen 2005). As a result, Japanese barberry now grows throughout the northeastern United States as far west as western North and South Dakota (Zouhar 2008). A very adaptable drought- and shade-resistant plant with very low rates of mortality, it grows in a range of habitats from open fields and meadows to wetlands to deep shaded forest, growing up to 8 feet (2.5 m) high, often in dense impenetrable thickets (Grebenstein 2013; Swearingen 2005; Ehrenfeld 1999). Its prolific and readily germinating bright red berries are widely spread by birds and small mammals, but white-tailed deer avoid eating the plant, giving it a competitive advantage over native species, which it easily and completely displaces. In addition to growth from seed, the branches of B. thunbergii root when they touch the ground and root fragments readily sprout to form new individuals, so it is persistant difficult to remove once established. As well as altering native wildlife habitat, Japanese barberry changes the ecology around it by raising the soil pH, altering nitrogen levels and biological activity in the ground, and reducing leaf litter depth in forests (Swearingen 2005; Kourtev et al. 1999; Silander and Klepeis 1999). The Plant Conservation Alliance’s working group lists it as one of the least wanted alien plant invaders of natural areas and recommends against planting it, however it has many popular cultivars and nurseries in the US commonly sell it for landscaping purposes (Swearingen 2005).
- Ehrenfeld, J. G. 1999. Structure and dynamics of populations of Japanese barberry (Berberis thunbergii DC.) in deciduous forests of New Jersey. Biological Invasions 1: 203-213.
- Grebenstein, E. 2013. Escape of the invasives: Top six invasive plant species in the United States. Research Topics, Smithsonian Science. Retrieved July 25, 2013 from http://smithsonianscience.org/2013/04/top-six-invasive-plant-species-in-the-united-states/.
- Kourtev, P.S., W. Z. Huang, and J. G. Ehrenfeld. 1999. Differences in earthworm densities and nitrogen dynamics in soils under exotic and native plant species. Biological Invasions 1: 237-245.
- Silander, J. A. and D. M. Klepeis. 1999. The invasion ecology of Japanese barberry (Berberis thunbergii) in the New England landscape. Biological Invasions 1: 189-201.
- Swearingen, J.M. 2005. Fact Sheet: Japanese barberry. National Park Service. Plant Conservation Alliance, Alien Plant Working Group. Retrieved July 25, 2013 from http://www.nps.gov/plants/alien/fact/beth1.htm.
- USDA Agricultural Resource Service, 2010. Barberry. Cereal disease laboratory. Retrieved July 25, 2013 from http://www.ars.usda.gov/Main/docs.htm?docid=9747
- Zouhar, Kris. 2008. Berberis thunbergii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Retrieved 2013, July 25 from http://www.fs.fed.us/database/feis/.