Berberis thunbergii DC.
Berberis thunbergii DC.
Author: Scott A. Mori and Jim Nordgren
Family name: Berberidaceae (Barberry Family)
Scientific name: Berberis thunbergii DC.
Etymology: Named after Carl Pehr Thunberg, a student of Linnaeus.
Common name: Japanese barberry
Description: Deciduous shrub, ranging from 0.5-2.5 m tall. Roots of two types: a taproot penetrating deeply into the soil, with a distinct yellow wood, and a wide network of diffuse roots just below soil surface. Stems sulcate (channeled), armed with thorns. Leaves arising from short shoots, simple, alternate but clustered: blades 1.3-3.8 cm long, obovate to narrowly obovate, the blade base tapered to base of petiole, the margins entire, the apex obtuse to rounded. Inflorescences with 1-4 flowers arising from apex of a peduncle. Flowers actinomorphic (radially symmetrical); petals with two yellow, large, nectaries at bases; stamens 5, the filaments grading into anthers, the anthers opening by lateral valves. Fruits red, single-seeded berries.
Ecology: A shade tolerant shrub that has invaded deciduous forests and many other habitats (including wet areas). Not found at higher elevations. This species is able to out compete native plants because of the following reasons: 1) it is one of the first shrubs to flush new leaves in the spring which allows it to photosynthesize before the leaves of trees create shade, 2) the shade produced by the barberry inhibits the photosynthesis of spring wildflowers and tree seedlings that grow under them, 3) the tap root makes it very difficult to eradicate the plants, 4) the diffuse and extensive fine root system of this invasive facilitates the uptake of water and nutrients that could be used by spring emphemeral wildflowers and seedlings of native trees, 5) the flowers, mostly because of the nectar they produce, attract a pollinators, 6) abundant fruits are produced and these are consumed and dispersed by small mammals and birds. According to (Ward et al., 2013) forests infested with barberry can impact human and pet health because the bushes create an environment favored by the mammal hosts of blacklegged ticks (Ixodes scapularis) which transmit Lyme and other diseases.
Distribution: Widely spread in the northeastern and midwestern United States as far west as the Rocky Mountains. It is not yet established in the extreme southern and western parts of the United States. This invasive species is found in high numbers throughout Westchester County..
Origin: Japan. Berberis thunbergii was introduced to North America in 1875 because of its resistance to wheat rust.
Phenology: Flowers from April to May and fruits in the late summer and fall.
Similar species: A closely related species, European barberry (Berbaris vulgaris), was introduced into North America by European settlers as an ornmental and for use in medicine and for the production of jam and dyes. Because it serves as an alternate host for wheat rust (Puccinia triticina) it was removed from areas where wheat is grown by the United States Department of Agriculture. Berberris japonica is not an alternate host for wheat rust so it was introduced into the United States as an ornamental that has now turned into an invasive plant that threatens the native flora. The two species are easy to distinguish from one another as the Japanese barberry has entire leaves and flowers that arise from the apex of the peduncle--whereas European barberry has serrate leaves and has flowers that are not clustered at the apex of the penduncle (see images). Unfortunately not all plants of the European barberry were eliminated and, as a result, some hybridization between the European and Japanese barberries takes place.
Control: In a limited area Japanese barberry is relatively easy to eradicate.Young plants can be removed by pulling them out without breaking their tap roots. When this is done the entire diffuse root system plant is removed along with the tap root. Once the plant gets bigger it is more difficult to remove without breaking the tap root which can subsequently resprout. The most important control methods are to refrain from planting species of barberrry as an ornamental plant. It is critical to remove plants from trail heads before they ripen fruit. Some invasive plant workers use a circular blade on the end of a weed wacker to cut barberry plants at ground level. Within 20 minutes after cutting they spray a very small amount of Roundup at a 5% concentration on the cut barberry stems. This method has been successful and uses 75% less herbicide than foliar spraying. Roundup has to be used with caution because of the health proplems it may cause to those who handle it as well as the negative ecological impacts it may have on native plants and animals. In addition local, county, state, and federal laws regulating herbcides must be followed before they are applied. Control of the Japanese barberry is reviewed in a bulletin published by the Connecticut Agricultural Experimental Station and the University of Connecticut (Ward, J. S., S. C. Williams & T. E. Worthley. 2013. Japanese barberry control methods for foresters and professional woodland managers. Special Bulletin of the Connecticut Agricultural Experiment Station and the University of Connecticut).
Floras and Monographs
Berberis thunbergii DC.: [Book] Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.