Japanese barberry

not listed

NNA - Not applicable

SNA - Not applicable

not listed

Restricted Noxious Weed

Japanese barberry was introduced in the 1800s as an ornamental and landscape plant. It was popular due to its colorful foliage, adaptability to urban environments, and resistance to deer browsing. It escaped cultivation and is now naturalized in Minnesota woodlands.

In favorable conditions it can create a monoculture that crowds out native species. Its dense foliage creates a microclimate favorable for black-legged ticks, making it a health concern to humans.

UPL - Obligate upland

FACU - Facultative upland

FACU - Facultative upland

Japanese barberry is an exotic, invasive, thorny shrub. It is native to Japan and has been cultivated around the world as an ornamental. It occasionally escapes cultivation and is now widely naturalized in Europe, China, and North America. It was introduced into North America in the 1800s. In the United States it is now common from Maine to Minnesota south to North Carolina and Missouri, with scattered populations in the west. In Minnesota it is common in the eastern half of the state with scattered populations in the western half. It is found in open, bottomland and upland woodlands; woodland edges and openings; pastures and meadows; yards; old fields, roadsides, and other disturbed places. It grows in well-drained, moist to dry soil under full sun to medium shade. It is a restricted noxious weed in Minnesota. The state recognizes – and prohibits – 25 cultivars in addition to the parent species.

Japanese barberry is a deciduous, woody, perennial shrub. It rises on multiple stems from a shallow root system that consists of underground, horizontal stems (rhizomes), a root crown, and many fine roots. It can be 1′ to 10′ in height, though in Minnesota it is rarely more than 6′ tall and usually no more than 3′ tall. It sometimes forms large, impenetrable thickets. The shrubs are dense, compact, and mostly wider than tall.

Two kinds of stems are produced, long stems and spur stems. Long, spiny, densely branched stems rise from the root crown. These stems are erect near the center of the shrub to lying on the ground with just the tips curved upward (decumbent). Additional young stems (shoots) rise at intervals along the rhizomes. Second-year stems are purple or brown, hairless, angular, and ridged. Older stems are striped in shades of brown. On large shrubs the oldest stems have rough, gray bark. Most of the leaves on long stems are replaced by single spines. The spines are stiff, about ½″ long, and usually unbranched, sometimes 3-branched. Short, leafy, spur stems are produced in the upper angle (axil) where each thorn attaches to the long stem. Two to six leaves are clustered at the end of each spur stem.

The leaves are alternately arranged but very closely spaced on the stem and usually do not appear alternate. They are widest toward the end, inversely egg-shaped or spatula-shaped, ½″ to 15 ⁄16″ (12 to 24 mm) long, and ⅛″ to ⅜″ (3 to 10 mm) wide. They may be stalkless or on 1 ⁄32″ to 5 ⁄16″ (1 to 8 mm) long leaf stalks. The leaf blade is thin, flexible, unlobed, long-tapered at the base, and rounded or broadly angled at the tip. The upper and lower surfaces are green, dull, and hairless. The margins are flat and untoothed.

The inflorescence is usually an umbrella-like cluster (umbel) of 2 to 5 flowers, sometimes just a single flower, at the end of each spur stem. The umbels are ⅜″ to ⅝″ (10 to 15 mm) long and are produced along the entire length of the long stem. Each flower droops at the end of a short stalk. At the base of each flower there are 3 small modified floral leaves (bracteoles). The bracteoles are membranous and narrowly angled at the tip. There are 6 outer floral leaves (sepals), 6 petals, 6 stamens, and 1 style. The sepals are petal-like, yellow, curved inward, widely spreading, and ⅛″ to 3 ⁄16″ (3 to 5 mm) long. The sepals and bracteoles are shed immediately after the flower fully opens. The petals are yellow and ⅛″ (2.3 to 3.0 mm) long. They are erect and curved inward, forming a protective cup around the reproductive parts of the flower.

The fruit is a bright red, juicy, globe-shaped or elliptical, ⅜″ (9 to 10 mm) long berry with 1 to 10 seeds. The berries remain on the plant throughout the winter.

1′ to 10′

Yellow

Moist to dry. Open, bottomland and upland woodlands; woodland edges and openings; pastures and meadows; yards; old fields, roadsides, and other disturbed places. Full sun to medium shade.

May through early June

Sources

2, 3, 4, 5, 7, 22, 28, 29, 30.

Native to Japan. Introduced, escaped cultivation, and and widely naturalized.

Common

Plant

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Inflorescence

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Cultivar