Thunberg's barberry is better known in the United States as Japanese barberry, a garden shrub that has spread into eastern forests. Its small smooth-edged leaves, single spines, and red berries make it recognizable through much of the year.
Appearance
Growth form
This dense deciduous shrub is often 3–6 ft (0.9–1.8 m) tall. Most stem nodes carry one sharp spine.
Leaves
The small spoon-shaped leaves have smooth edges. Garden forms may have green, purple, or yellow foliage.
Flowers
Creamy yellow flowers appear alone or in small groups in spring.
Fruit
Bright red berries can remain on the branches into winter. Birds eat the fruit and spread the seeds.
Common barberry has clearly toothed leaf edges and usually three-part spines. Japanese barberry usually has smooth leaf edges and one spine at each stem node.
Why they get mixed up · Both are thorny shrubs with yellow flowers and red fruit.
Allegheny barberry has toothed leaves and usually three-part spines. Japanese barberry has smooth-edged leaves and single spines.
Why they get mixed up · Both can look like low, thorny barberry shrubs.
Where it lives
Typical habitats
Garden hedges
Forest understories
Range
Native to Japan, it is introduced across parts of the United States. It is considered invasive in North Carolina and has spread into Pennsylvania woods.
Name and classification
About the name
Ottawa barberry (Berberis × ottawensis) is a hybrid between Japanese barberry and common barberry (Berberis vulgaris).
Varieties and forms
Purple-leaved 'Atropurpurea' and yellow-leaved 'Aurea' are cultivated forms of this species. Some newer cultivated lines are bred to produce few or no seeds that can sprout.
Conservation
IUCN Red List
NENot Evaluated·Not yet assessed
Threats
In eastern U.S. forests, dense stands can crowd out native plants. Research in the Northeast has also found more blacklegged ticks in barberry thickets.