Japanese Barberry

Common Name: Japanese Barberry
Scientific Name: Berberis thunbergii DC

Legal Status

Restricted

Propagation and sale of the following cultivars are prohibited in Minnesota.  Transportation is only allowed when in compliance with Minnesota Statute 18.82.  Although Restricted Noxious Weeds are not required to be controlled or eradicated by law, landowners are strongly encouraged to manage these invasive plants on their properties in order to reduce spread into new areas. 

Background

Japanese barberry was introduced to North America in the 1800s as a popular ornamental and landscape plant. Grown for its interesting foliage colors, deer resistance and adaptability to urban growing conditions, Japanese barberry has been discovered naturalizing in understory wooded areas in Minnesota.

Description

• Japanese barberry spreads by seed, and can be a prolific seed producer. Birds eat the seed-containing fruit, facilitating spread to new areas. Cultivars that produce less seed pose a lower risk than high-seeding cultivars, though research suggests that the only completely safe cultivars of long-lived woody species are completely sterile cultivars.
• Japanese barberry is a woody shrub with curving branches that have numerous sharp spines. The plant can grow six feet or taller.
• The leaves are small, rounded, and arranged in clusters above the spines. Japanese barberry cultivars can range in color from chartreuse, gold, maroon, and green. Most naturalized Japanese barberry plants found to date have green leaves in the summer followed by vibrant orange and red fall foliage.
• Small yellow flowers bloom in May, followed by red oblong berries that persist into winter.

Habitat

Japanese barberry is adapted to many soil types and can grow in full sun to shade. In Minnesota it has been found naturalizing in wooded areas, forming large, impenetrable thickets.

Means of spread and distribution

Japanese barberry seeds are spread by birds; plants also spread vegetatively by low branches that will root when they come in contact with soil. It is also spread through intentional ornamental and landscaping plantings.

Impact

Japanese barberry infestations cause many detrimental ecological and economic impacts. It has the unique ability to change the chemistry of the soil beneath the plant, which in turn makes the site more favorable for additional Japanese barberry plants. Over time, the change in soil pH and the higher nutrient levels can contribute to changes in the whole ecosystem of the area, resulting in a decrease of native plant and animal biodiversity. Because deer do not browse on Japanese barberry, they will also contribute to native species decline in infested areas by feeding on the easier-to-eat native plants in the area. The dense stands of Japanese barberry effectively become a monoculture, replacing the diverse, native understory with one species. Japanese barberry invasion reduces the carrying capacity of wooded pasture and limits the movement of livestock. Cattle and other large animals cannot move through the thorny thickets.

Dense stands of naturalized Japanese barberry could result in public health concerns as well. Research in Connecticut and Maine showed that black-legged ticks were twice as numerous in Japanese barberry infestations as in non-invaded areas. Dense Japanese barberry growth creates a microclimate with the ideal humid conditions that ticks prefer. As the carriers of the bacteria that cause Lyme disease, increased tick populations could lead to more cases of Lyme and other tick-borne diseases in humans, pets, and livestock.

Prevention and Management

• A two-step combination of mechanical and chemical treatments may be the most effective way to manage Japanese barberry. Mechanical (hand-pulling, cutting, mowing, or using brush saws) methods can be used as an initial treatment, but to be most effective, they need to be followed by herbicide treatments.
• Foliar or cut-stump herbicide applications can be effective. For specific herbicide recommendations, contact your local University of Minnesota Extension agent or check Midwest Invasive Plant Network Control Database recommendations. Resprouts should also be treated with an herbicide application.
• Controlled burning may also be effective. Make sure to contact the Minnesota Department of Natural Resources to learn more about control burning practices and regulations.