JAPANESE BARBERRY (Berberis thunbergii) is an invasive woody shrub that invades meadows, forest, wetlands and other natural areas. Native to Japan, the shrub was introduced to the U.S. as an ornamental in 1875. It escaped cultivation and is now is widespread in the northeastern United States. The shrub is found from northern Quebec south to Georgia, west to the Dakotas and Wyoming, and in two counties in Washington (Figure 1).
Japanese barberry is listed as prohibited in Michigan and Massachusetts (USDA-NRCS 2017), and is considered invasive in about 20 states and five Canadian provinces (Ward et al. 2013a). The plant continues to be a popular landscape ornamental with several varieties sold to the public.
IDENTIFICATION AND SPREAD
Japanese barberry is a compact, deciduous, spiny shrub from two to eight feet tall. Branches have a single sharp spine at each node. Leaves are oval, bluish-green to reddish and are ½ to 1 ½ inches long. Pale yellow flowers about ¼ inch in diameter hang in clusters along the stem (Figure 2). Fruits are bright red berries about 1/3 inch long and mature from late summer to fall, persisting on stems through winter (Figure 3). Japanese barberry reproduces primarily by seed that is dispersed by birds and small mammals. Most seed germination occurs the growing season following seed maturity. Vegetative reproduction occurs when branches touching the ground root and form new plants.
Barberry is drought resistant, grows in full sun to shade, and is capable of occupying a wide range of ecological sites. The plant forms dense stands that inhibit forest regeneration and native herbaceous plants, alter soil structure and function, and can impact human health by creating an environment that supports high populations of blacklegged tick (Ixodes scapularis). [SIDEBAR 1]
Japanese barberry infestations are favorable habitat for blackleg ticks, providing a humid, buffered microclimate that increases tick survival. Ticks can transmit several diseases including Lyme disease Borrelia burgdorferi, anaplasmosis, and human babesiosis. The shrub also provides nesting areas for white-footed mice and other rodents, which are primary sources for larval ticks’ first blood meal, and reservoirs for Lyme disease. The number of blackleg ticks averaged 120 per acre in barberry infested forests compared to 10 per acre in forests without barberry present. (Image from Ward et al. 2013b).
Lyme disease quiz http://www.emedicinehealth.com/ticks/article_em.htm
For additional information on high volume foliar and basal application methods for woody plant control go to http://techlinenews.com/prairieguide/2015/woody-plant-control-in-northern-prairies.
Barberries generally leaf-out earlier and retain their leaves longer than many native shrubs. This trait aids in early detection and management. The most effective landscape-level control for Japanese barberry is early detection and control of small, newly expanding populations.
Foliar Spray Method: Best suited to large Japanese barberry infestations. Applications should be made with a coarse spray to reduce drift and thoroughly wet all leaves.
Remedy® Ultra herbicide and Vastlan™ herbicide are selective for broadleaf plants and can be applied to barberry in areas with a desirable grass understory. Field trials conducted from 2004 through 2006 showed that either Remedy at 0.5 to 1 percent solution or Vastlan at 1 gallon per acre (1 percent solution) plus 0.5 percent non-ionic surfactant, provided 100 percent control of Japanese barberry one year after application.
Glyphosate (Accord® XRT II herbicide and other trade names) is a non-selective herbicide that may cause significant injury to desirable grasses and broadleaf vegetation. If damage to desirable non-target vegetation can be tolerated, apply a 2 percent solution of glyphosate in water (Table 1) plus a 0.5 percent non-ionic surfactant. [See Table 1. Rates for percent herbicide solution]
Cut Stump Method: Cut stump treatments selectively control individual Japanese barberry plants and can be used as long as the ground is not frozen.
Cut barberry stems horizontally at or near ground level. Immediately apply a 25 percent solution of either Remedy® Ultra herbicide mixed with water to the cut stump.
Hand Pulling: Japanese barberry is one of the first plants to leaf out in spring making it easy to distinguish from other shrubs. Hand digging with a shovel or weed wrench effectively removes individual Japanese barberry plants and can be done any time ground is not frozen. Wear heavy gloves to protect hands from spines. Remove as much of the root as possible since barberry can resprout. Barberry plants with fruits present should be bagged and removed from the site to prevent establishment from seed. Minimize soil disturbance during the removal process to reduce invasion of other undesirable plants.
Mowing/Cutting: Small barberry populations or those growing in sites where herbicides cannot be used can be mowed or cut to prevent seed production. Cutting at least one time per growing season will stop seed production; however, even repeated cutting may not kill established plants. Hand-cutting established populations is difficult and time consuming due to the long arching stems and prolific thorns.
Directed flame/torch: Field studies have shown that individual barberry plants can be controlled with direct intense heat from a propane torch or flame weeder. Basal buds on the plant crown must be killed to control the plant. A two-step process that combines fire or mowing to reduce above ground biomass followed by herbicides to control resprouts can be effective. Labor costs for follow-up treatments with the torch were at least four times higher than for herbicide applications, although both were equally effective at controlling barberry (Ward et al. 2013a).
Appollonio, Jennifer, “Regeneration Strategies of Japanese Barberry (Berberis thunbergii DC.) in Coastal Forests of Maine” (2006). Electronic Theses and Dissertations. Paper 433. http://digitalcommons.library.umaine.edu/cgi/viewcontent.cgi?article=1399&context=etd.
DeGasperis BG and G Motzkin. 2007. Windows of opportunity: historical and ecological controls on Berberis thunbergii invasions. Ecology 88(12):3115-3125.
DowAgroSciences. 2017. Internal data from herbicide field trials.
EDDMapS. 2019. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/. Accessed June 7, 2019.
Silander JA and DM Klepeis. 1999. The invasion ecology of Japanese barberry (Berberis thunbergii). Biological Invasions 1: 189–201 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.530.6006&rep=rep1&type=pdf.
USDA, NRCS. 2019. The PLANTS Database (http://plants.usda.gov, 07 June 2019). National Plant Data Team, Greensboro, NC 27401-4901 USA.
Ward JS, TE Worthley, and SC Williams. 2009. Controlling Japanese barberry (Berberis thunbergii DC) in southern New England, USA. Forest Ecol. Manag. 257: 561–566.
Ward JS, SC Williams, and TE Worthley. 2013a. Comparing Effectiveness and Impacts of Japanese Barberry (Berberis thunbergii) Control Treatments and Herbivory on Plant Communities. Invasive Plant Science and Management 6(4):459-469. http://www.bioone.org/doi/abs/10.1614/IPSM-D-13-00004.1.
Ward, JS, SC Williams and TE Worthley. 2013b. Japanese barberry control methods. Univ. Connecticut Coop. Ext. Special bulletin. Available online at http://www.ct.gov/caes/lib/caes/documents/publications/special_bulletins/special_bulletin_feb_2013_ward.pdf.
Williams SC and JS Ward. 2010. Effects of Japanese Barberry (Ranunculales: Berberidaceae) Removal and Resulting Microclimatic Changes on Ixodes scapularis (Acari: Ixodidae) Abundances in Connecticut, USA. Environmental Entomology 39:6 1911-1921.
Published in April 2017; reviewed and updated June 2019.
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Active ingredients for products mentioned in this article. Product (active ingredient): Accord XRT II (glyphosate); Remedy Ultra (triclopyr-ester); Vastlan herbicide (triclopyr-amine).