🔴 Invasive - Remove
Japanese Barberry
Berberis thunbergii
This is an invasive species that harms native ecosystems. It should be removed when found to protect local plant and wildlife habitats.
Berberis thunbergii
This is an invasive species that harms native ecosystems. It should be removed when found to protect local plant and wildlife habitats.
A dense, thorny shrub with small oval leaves, single sharp spines at each node, and bright red berries that hang on all winter. Escaped from foundation plantings into the forest understory, where it forms thickets that shelter black-legged ticks.
Native to: Japan
Introduced through the Arnold Arboretum in 1875 as a replacement for common barberry, which spread wheat rust. It became a standard landscaping hedge and is still sold in many colours.
Forms thickets that shade out native shrubs and wildflowers and change soil chemistry. Its humid microclimate is prime habitat for the ticks that carry Lyme disease; studies find several times more infected ticks in barberry stands. Birds spread the berries.
Colour and texture: Small, smooth-edged, spoon-shaped leaves in tufts along the stem, green or deep burgundy depending on the cultivar. Single sharp spines at each tuft, and the inner wood is bright yellow when you cut it.
Leaves: small, oval to spoon-shaped, smooth-edged, in clusters; green or purple-red depending on the cultivar. Leafs out in March before most natives.
Spines: a single sharp spine at the base of each leaf cluster (native barberry has three-pronged spines).
Berries: bright red, oblong, hanging singly along the stems from autumn through winter.
Wood: the inner bark and wood are bright yellow.
Berries September through the winter.
Small, bright red, oval berries hanging singly along otherwise bare stems. They are still there in February, which is the easiest month of the year to spot the shrub.
Why it matters: Barberry thickets hold humidity and are reliably the tickiest ground on a site. Winter is both the best time to find it and the safest time to work it.
A woody crown too big to pull and too stubborn to cut: wineberry, multiflora rose, barberry, bush honeysuckle, tree seedlings.
Avoid: Do not clamp halfway up the stem. It snaps, and the crown stays in the ground and re-sprouts.
It can stay on site. Wrenched crowns can stay, piled off the soil with the roots up.
American barberry, Berberis canadensis, is native but rare here; it has toothed leaves and three-branched spines. Japanese barberry leaves are smooth-edged and its spines are single.
Before the first cut: Barberry thickets are tick country. Long sleeves tucked in, and check yourself when you get home.
Wrench the whole shrub. Barberry roots are shallow, so a or a firm pull on a small plant lifts the entire root ball.
Best window: early spring, when it is the only green shrub in the woods, or after leaf-fall. Check yourself for ticks afterwards regardless.