There are two types of non-native, invasive barberry, Japanese barberry (Berberis thunbergii) and common barberry (Berberis vulgaris). They are both sun and shade tolerant and can therefore grow in many places including closed canopy and open woods, forest borders, fields, wetlands, and roadsides. In Vermont, barberry is most prevalent in Chittenden and Windsor counties.
Barberry is a shrub between 1 and 6 ft. tall. It is most easily identified by its spatula-shaped leaves that appear early in the spring. The leaves vary in color from a bluish green to reddish purple. Japanese barberry leaves have smooth edges while common barberry has serrated leaves. Barberry has small, yellow flowers that hang below the stem and appear between April and May. Its fruit is bright red, small, oblong berries that mature later in the summer and into fall and last throughout the winter. Japanese barberry has single spines along its branches. Common barberry has three-branched spines at the base of each cluster of leaves. Barberry has yellow inner bark, seen when cut or scratched.
Barberry grows and spreads rapidly and can quickly form dense stands in the habitats it invades. It crowds out native shrubs and other plants.
Deer avoid eating barberry, which helps it out compete native vegetation. Barberry stands are also linked to increased rates of Lyme disease. Higher densities of deer ticks and deer mice, the larval host of these ticks, have been found under barberry compared to native shrubs.
Control and Prevention
Mechanical removal is quite effective in controlling barberry infestations due to the plants’ shallow root systems. Plants can be pulled throughout the year whenever the ground is soft enough. Small plants can be hand pulled, but use caution to avoid the spines. Larger plants can be removed using a weed wrench or shovel. If a plant or infestation is too large for easy removal, mowing before seed production can limit population growth.
Herbicides have also been found effective in controlling barberry populations either by applying them to cut stumps or spraying on leaves. For large infestations or populations near sensitive areas like waterbodies and wetlands, a professional should be contacted for chemical treatment.
The most important prevention method is to avoid an initial introduction of barberry. Carefully choose what shrubs to plant when landscaping and do not plant barberry in yards or gardens. Barberry may seem tempting to plant because deer do not eat it, but the consequences of a barberry infestation far outweigh a few lost shrubs.
Barberry is on the Vermont Noxious Weed Quarantine list and so is illegal to purchase, plant, and transport barberry in the state.
Native Plant Sources
Check out Native Plant Sources for places to purchase plants native to Vermont.