Japanese barberry

Japanese barberry is reported frequently throughout the Great Lakes region. USDA reports Japanese barberry as being hardy to a minimum temperature of -28^oF (Zone 4a), though a few isolated verified reports in northern Minnesota indicate it may occasionally be able to establish in Zone 3b as well. It is most commonly reported in the Midwest, the Mid-Atlantic, and in New England. Particularly dense infestations can be expected in areas where the species has been or still is popular as an ornamental landscape plant. 

Additional invasive species distribution data for specific Great Lakes jurisdictions are available via:

• Midwest Invasive Species Information Network (Michigan)
• iMapInvasives (New York and Pennsylvania)
• EDDMapS Ontario

Although birds can eat and transport Japanese barberry fruit and seeds over long distances, it is not usually a preferred food. Many of the fruits are not eaten and fall close to the parent plant resulting in thicket-like populations. However, distribution significant distances from known populations does occur (Michigan Natural Features Inventory 2012). Japanese barberry can also spread locally through vegetative reproduction, both by sprouting from rhizomes and by growing new roots where stems come in contact with the ground (Zouhar 2008).

Japanese barberry invades open and forested areas, including old fields, edge habitats, woodlands, transport and utility right of ways, and streambanks. It is very shade tolerant and can dominate forest understories. Japanese barberry also tolerates a broad range of soils and moisture levels. It is more prevalent in disturbed sites and secondary growth (e.g., reforested agricultural land) than in remnant ecosystems (Zouhar 2008).

Its high level of seed production and vegetative spread enable Japanese barberry to form impenetrable thickets within natural habitats where it out-competes desirable shrubs and herbaceous plants. Research has indicated that Japanese barberry can increase soil nitrogen and carbon cycling rates while increasing soil alkalinity in invaded ecosystems, further impacting native plant communities (Ehrenfeld 2003). 

Thickets of Japanese barberry create ideal cover for rodents, including white-footed deer mice (Peromyscus leucopus). These mice often host and contribute to the spread of black-legged ticks (Ixodes scapularis), which carry the bacteria responsible for Lyme disease. Dense growth of the Japanese barberry contributes to a humid microclimate near the ground, which increases tick feeding activity and overall survival leading to notably larger populations. A study from Connecticut found higher numbers of ticks infected with the bacteria that causes Lyme disease in areas infested with Japanese barberry than in both uninfested areas and areas where the invasive shrubs had been controlled (Williams & Ward 2010).

Japanese barberry was first introduced to North America in the early 1800s. However, it didn’t become popular in horticulture until more than 100 years later, when it was promoted as a disease-resistant alternative to common barberry (Zouhar 2008). Today, Japanese barberry is still a popular landscape plant and dozens of cultivars have been produced and marketed (Dirr 2008). It is used as a foundation planting (close to buildings or other hardscaping), as a mass planting, and as a low-maintenance hedge that serves as a barrier to foot and animal traffic due to its dense growth and thorns.

Plant propagators have developed and released several less seedy cultivars of Japanese barberry. However, cultivars may exhibit low-fruit production for the first few years of the plant’s life (the typical duration of cultivar trials), but as the plants age, they become capable of producing considerably more fruit and seed (Brand et al. 2012). Other research has found that seeds produced from these cultivars do not retain this low seed production trait (Knight et al. 2011). Thus, the next generation of plants may be as capable of contributing to invasions as the high seed producing varieties. Research suggests that long-lived species, such as Japanese barberry, can contribute to invasive population growth over time even if they are low seed producing cultivars (Knight et al. 2011). The Great Lakes jurisdictions have taken different approaches to regulating Japanese barberry cultivars, with one state regulating all cultivars, one state exempting a handful of relatively new cultivars tested as functionally sterile, and two states exempting all but the highest seed producing cultivars. 

Please see our Landscape Alternatives pages for more information about how the WIGL Collaborative selected alternatives.

^a Not all Japanese barberry has purple foliage – the variety ‘atropurpurea’ does, as do cultivars bred from this variety. Other types are typically light to dark green.
^b Species is dioecious (male and female parts occur on different plants), and only female plants form fruit. The recommended cultivar is female, but will need to be paired with a male to produce fruit.
^c Listed cultivars have the indicated trait, but the straight species may not. The straight species of native plants may provide better pollinator benefits.
^d Only male cultivars, such as the one listed, are recommended due to improved disease resistance.

Green = native to part of the Great Lakes Basin
Yellow = native to the United States but not to the Basin
Blue = not native but not invasive

Please see our Landscape Alternatives landing page for more information about how the WIGL Collaborative selected alternatives for each species.

^a Not all Japanese barberry has purple foliage – the variety ‘atropurpurea’ does, as do cultivars bred from this variety. Other types are typically light to dark green.

^b Species is dioecious (male and female parts occur on different plants), and only female plants form fruit. The recommended cultivar is female, but will need to be paired with a male to produce fruit.

^c Listed cultivars have the indicated trait, but the straight species may not. The straight species of native plants may provide better pollinator benefits.

^d Alpine currant is dioecious (male and female parts occur on different plants), and only female plants form fruit. However, generally only male cultivars, such as the one listed, are recommended due to improved disease resistance.

Green = native to part of the Great Lakes Basin
Yellow = native to the United States but not to the Basin
Blue = not native but not invasive

The WIGL Collaborative’s decision trees are designed to help site users, who are perhaps newly discovering that plants that are part of their home landscaping are invasive, prioritize which species should be removed first based on risk to the surrounding environment, economy, and occasionally, to human health. In a perfect world, everybody would remove all invasive plants from their landscaping right away, but in reality, removing mature woody plants involve a hefty investment of time and/or money. These diagrams can help people with multiple woody invasives in their landscaping prioritize to get the most benefit for their efforts.

To learn more about the methodology and information used to develop the decision trees and for helpful hints on how to answer the questions, please see the full report here (PDF).

The following is a brief overview of management techniques shown to be effective on Japanese barberry. For more detailed information on how to use these techniques, please visit our Management and Control page. For technical assistance on managing woody invasive species, please get in touch with a local cooperative invasive species management group.

Timing and spread concerns: Early detection is an advantage in managing any invasive species. Individual plants should be controlled before they fruit in order to prevent spread. If control is undertaken after plants have fruited, it is best not to remove the plants from the site to avoid spreading seed. 

Physical control: Small plants are easily hand-pulled from moist soil and larger plants can be dug or pulled using equipment. Roots must be removed to prevent resprouting, but the root system is relatively shallow compared to many other invasive shrubs, especially when it is growing in a shaded habitat (Michigan Natural Features Inventory 2012). Cutting, mowing, and other practices that do not impact the root are not effective as stand-alone practices, but can be combined with herbicide treatment or directed heating. Managers in New England have documented success using directed heating with specialized propane torches to flame girdle Japanese barberry on relatively small ecologically sensitive sites (Ward and Williams 2011). Similarly, prescribed fire is effective at controlling this species when applied repeatedly in fire-adapted habitat types (Zouhar 2008).

Chemical control and combined approaches: Cut stump and basal bark herbicide treatment are effective and can be applied year-round with limited exceptions, though basal bark treatment may not be feasible on extensively multi-stemmed individuals. Foliar spray may be the most feasible control method for a large, dense infestation, and is effective when plants are actively growing, including early spring and late fall while most desirable herbaceous plants are dormant. In all cases, herbicide should be selected carefully based on site conditions, and label directions read and followed carefully. 

With any treatment it will be necessary to monitor for and treat regrowth and new seedlings in subsequent years.

Resources on management of Japanese barberry:

• Michigan Natural Features Inventory
• Midwest Invasive Plant Network Control Database
• University of Connecticut
• University of Wisconsin Extension
• University of Wisconsin Extension – Woody Invasive Plant Management Demos

• Brand, MH, Lehrer, JM, and JD Lubell. 2012. Fecundity of Japanese barberry (Berberis thunbergii) cultivars and their ability to invade a deciduous woodland. Invasive Plant Science and Management. 5(4): 464-76.
• Dirr, MA. 1998. Berberis thunbergii. In: Manual of Woody Landscape Plants, Fifth Edition. Champlain, IL: Stipes Publishing. pp122-125.
• Ehrenfeld, JG. 2003. Effects of exotic plant invasions on soil nutrient cycling processes. Ecosystems. 6(6): 503-23.
• Knight, TM, Havens, K, and P Vitt. 2011. Will the use of less fecund cultivars reduce the invasiveness of perennial plants? BioScience. 61(10): 816-22.
• Lehrer, JM and MH Brand. 2010. Purple-leaved Japanese barberry (var. atropurpurea) genotypes become visually indistinguishable from greenleaved genotypes (Berberis thunbergii DC.) at low light levels. Journal of Environmental Horticulture. 28(3): 187-189.
• Michigan Natural Features Inventory. 2012. Japanese barberry (Berberis thunbergii). In: Invasive Species – Best Control Practices. 2/12/2019.
• 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): 1911-21.
• Zouhar, K. 2008. Berberis thunbergii. In: Fire Effects Information System (Online). U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. 1/7/2019.