Frangula alnus Mill.
Rhamnus frangula L. var. angustifolia Loudon
Rhamnus frangula L.
Rhamnus frangula L. ssp. columnaris hort.
Rhamnus frangula L. var. angustifolia Louden
European buckthorn, alder buckthorn
Alder buckthorn is native to Europe, Africa, and Asia. It was introduced to North America, where it has become naturalized. Frangula means “brittle wood,” and alnus means alders, which are often found in the same habitats. Alder buckthorn actually has no thorns, though relatives in the Rhamnus genus often do. In many areas it is considered an invasive.
Identification: This shrub reaches 9½-20' (3-6 m). It usually has multiple stems, rarely only one, becoming a tree. Dark brown-black bark covers a light yellow interior bark. Leaves are roughly oval, 1-2½" (3-7 cm) long and ⅞-1½" (2.5-4 cm) wide. Leaves have prominent veins and stems ¼-½" (8-15 mm) long. Flowers are ¹/₁₆-³/₁₆" (3-5 mm), 5-petaled, yellowish- or greenish-white, and inconspicuous. Clusters of shiny black berries, reddish or purplish before ripening, are each ⅛-⅜" (6-10 mm) in diameter.
Here are some similar-looking buckthorns:
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|Plant||This smaller shrub reaches up to 3' (1 m) in height.||Plants are rounded shrubs or small trees up to 33' (10 m) in height, with trunks that sometimes reach 10" (25 cm) in width. Outer bark is dark gray, while the inner bark is yellow and the heartwood is pink to orange in color. Stem tips are often tipped with a spine.||9½-20' (3-6 m) tall. It usually has multiple stems, rarely only one, becoming a tree. Dark brown-black bark covers a light yellow interior bark.|
|Flowers||Yellowish-green, 5-petaled, in groups of 1-3, nestled at the base of leaves, from May to July. Male and female flowers are on different plants.||Yellowish-green, with four petals, in dense clusters.||¹/₁₆-³/₁₆" (3-5 mm), 5-petaled, yellowish- or greenish-white, and inconspicuous.|
|Leaves||Alternate, elliptical, either rounded or pointed at the tip, smooth-edged, up to 4" (10 cm) × 2" (5 cm).||Elliptic (roughly oval), with several prominent veins roughly parallel to the leaf edges and fine teeth. They are ⅞-3½" (2.5-9 cm) × ⅜-1¼" (1.2-3.5 cm) in size. Leaves are mostly opposite, occasionally alternate, smooth on top and bottom.||Roughly oval, 1-2½" (3-7 cm) long and ⅞-1½" (2.5-4 cm) wide. Leaves have smooth edges and prominent veins and stems ¼-½" (8-15 mm) long.|
|Fruit||Round, up to ¼" (6.3 mm) in diameter, turning to light red and then to deep black. Each fruit contains three seeds.||Fruits are dense clusters of black berries ⅛-⅜" (6-10 mm) in diameter. Each berry contains 3-4 seeds.||Clusters of shiny black berries, reddish or purplish before ripening, are each ⅛-⅜" (6-10 mm) in diameter.|
Frangula alnus on Wikipedia
Frangula alnus on the USDA Forest Service's Fire Effects Information Database
Frangula alnus on Invasive.org, Center for Invasive Species and Ecosystem Health
Frangula alnus on Plants for a Future, a resource and information centre for edible and otherwise useful plants
Frangula alnus at Harvard Forest
Frangula alnus on Wikimedia Commons
Frangula alnus on the Ecology of Commanster
Petrides, George A., Peterson Field Guides: Trees and Shrubs, Houghton Mifflin Co., 1972, p. 267
Frangula alnus description by Thomas H. Kent, last updated 25 May 2020.