Frangula alnus aka European Alder

Frangula alnus is known as alder buckthorn or glossy buckthorn. It belongs to the buckthorn family, Rhamnaceae. Its native range spans Europe, central Siberia, Xinjiang, and northwestern Africa. It is native to Britain and Ireland too. It grows in damp woods, swamps, and other wet places. This deciduous shrub can also form a small tree. Several stems support an upright, spreading crown.

Garden plants often reach 10–16 feet [3–5 metres] tall. Some tree forms reach 20 feet [6 metres]. RHS gives a broader height range of 13–26 feet [4–8 metres]. Spread is often 8–13 feet [2.5–4 metres], though some plants grow wider. Older bark is grey, with a rough or wrinkled surface. Young brown branches carry many pale lenticels. The simple leaves grow mostly in an alternate pattern. They are oval, glossy, and dark green above. Their curved side veins stand out against the leaf blade. Fall leaves turn yellow, sometimes with red tones.

Small cream-green flowers appear in late spring and early summer. They grow beside the leaves, alone or in small groups. Bees visit them, though the flowers make little visual impact. The round fruits are drupes, each holding one to three seeds. They pass through green, yellow, and red before turning dark. Fruit can ripen at different times along one stem. Birds eat the fruit and carry seeds to new sites. Leaves feed the larvae of the yellow brimstone butterfly.

Grow this shrub in moist soil that drains well. It accepts full sun or some shade. Clay, loam, sand, and chalk can all suit it. It also grows across acid, neutral, and alkaline soils. Avoid soil that stays waterlogged. NC State lists USDA zones 2–7; RHS rates it H7. It suits hedges, screens, and woodland or wildlife gardens. It needs little routine pruning; trim hedges in early spring. Its wood supplies veneer, wooden nails, and charcoal for artists. Bark has a history of use as a laxative. This does not make the plant safe to eat.

Suckers and bird-carried seeds help it spread beyond gardens. It is invasive in parts of northeastern and midwestern North America. RHS reports few usual pest or disease problems. Other sources list aphids, scale, beetles, leaf spots, rust, and cankers. Root nematodes can also cause damage. The fruit can cause nausea, vomiting, and diarrhoea in people. RHS also warns that eating it can harm dogs. No edible uses are reported.