Frangula alnus

Native to Europe, Asia, and northern Africa. Introduced and naturalized in North America.

Invasive. Restricted noxious weed.

Wet to moist. Forest margins, river banks, lake shores, calcareous wetlands, ditches. Full sun to partial shade.

Late May to mid-August

Yellowish or greenish

up to 23′

This is a fast-growing tall shrub or small tree that rises on 1 or more stems. It can be up to 23′ tall and up to 4″ in diameter at breast height, though in Minnesota it is usually no more than 18′ in height.

The crown is open and spreading.

The bark is smooth, thin, gray or grayish-brown, with prominent, warty, slightly raised lenticels. On older stems the bark may become shallowly fissured.

First-year twigs are slender and greenish and/or reddish-brown. They are covered with minute, fine, gray hairs, at least on the last ½″, though this may require a hand lens to see. Second-year twigs are brown with a gray, flaky outer layer. There is no thorn at the tip of the twig. Buds are tan or rust-colored. They have no scales but are instead covered with a shriveled up leaf. Leaf scars have 3 bundle scars.

The leaves are alternate, deciduous, inversely egg-shaped to elliptical, 1½″ to 3″ long, and 1″ to 1½″ wide. They are on hairy, 3 ⁄16″ to ¾″ long leaf stalks. They are tapered at the base and abruptly pointed or occasionally rounded at the tip. There are 6 to 9 lateral veins on each side of the midrib. The veins are straight and parallel but curve up near the margin and follow the margin. They are depressed on the upper side of the leaf and stand out on the underside. The upper surface of the leaf blade is dark green, hairless, and glossy, giving this plant its common name. The lower surface is somewhat paler green and dull. It is sometimes hairless, more often covered with minute hairs at least along the main vein, though this may not be visible without a hand lens. The margins are untoothed. The leaves stay green into late fall.

The inflorescence is a stalkless, umbrella-like cluster (umbel) of 1 to 8 flowers rising from the leaf axils of the current year’s twigs.

The flowers are bell-shaped, small and inconspicuous, ⅛″ to 3 ⁄16″ wide. They have 5 yellowish or greenish petals. Each flower is on a ⅛″ to ⅜″ long, usually hairy flower stalk. They appear in late May to mid-August after the leaves have formed.

The fruit is a berry-like, ¼″ to 7 ⁄16″ in diameter drupe. It is green at first, soon turning red, eventually turning purplish-black at maturity. It matures in early August to late September and falls to the ground before winter. The flowering period is very long. It is not unusual to see flowers and fruits at various stages of maturity on the same twig.

Common buckthorn (Rhamnus cathartica) has thorns at the end of many of its twigs. The leaves are usually sub-opposite or opposite, only occasionally alternate. There are 3 to 5 strongly curved lateral veins on each side that arch toward the tip. The upper surface is not glossy. The margins are finely toothed. The flowers and fruit are in clusters of no more than 5. The fruit remains on the twig long into winter.