Berberis thunbergii is a small deciduous shrub from 2-8 ft. (0.6-2.4 m) tall. The thin, grooved branches have thin, straight spines. Berberis thunbergii is very shade-tolerant and can form dense stands which shade out and displace native species.
Foliage
The leaves are up to 1 in. (24 mm) long and paddle-shaped.
Flowers
The pale-yellow flowers occur in drooping clusters of 2-5 and develop in mid-spring to early summer.
Fruit
The berries ripen to a bright red color and are 0.25-0.3 in. (7-10 mm) long.
Ecological Threat
Berberis thunbergii invades a variety of habitats from shaded woodlands to open fields and wetlands. Berberis thunbergii is rapidly spread by birds that eat the berries thus dispersing the seeds. It is native to Asia and was first introduced into The United States in 1864 as an ornamental. It is still widely planted for landscaping and hedges.