Like its relative Purging Buckthorn, this small tree is easily overlooked, though it has ornamental merit, bearing attractive red fruits that turn purple-black. Charcoal made from its wood has explosive potential, contrasting with the quiet nature of this diminutive tree.
This species has a very wide range across several biomes, native across the whole of Europe including Britain and Ireland, north-west Africa, and east to China and Siberia. It is uncommon across much of Scotland and Ireland (except the Midland Region), otherwise found on acid soils, often on heathland and wetland fringes, growing with Black Alder, hence its common name. Where introduced in parts of North America it is invasive, hard to control through prolific seeding and suckering.
Monoecious, hermaphrodite flowers. Insect-pollinated. Distributed by birds and small mammals.
Small (6m), often bushy with slender branches above a short trunk. Bark pale grey, smooth. Twigs noticeably straight and thornless, pale red-brown with distinctive pale elongated lenticels, soon glabrous, with tiny scaleless woolly alternate buds. Leaves 3-8cm, oval to obovate and fairly narrow, abruptly pointed, glossy green above, paler and slightly downy below, with 8-9 vein pairs running out to entire (untoothed) margins. Flowers tiny (5mm), star-like, green, clustered in leaf axils. Fruit a globular berry (10mm), red ripening purple-black, persisting into winter. Purging Buckthorn differs: alkaline soils, spined twigs, forward-curving veins.
A hardy tree that will grow under a wide variety of conditions. It is very shade-tolerant. Tendency to sucker can be a problem when growing in hedges.
A larval food plant for the Brimstone butterfly (Gonepteryx rhamni). Fruit remains on tree long into the winter, sustaining many birds, especially visiting Fieldfare (Turdus pilaris), Redwing (T. iliacus) and Bohemian Waxwing (Bombycilla garrulus).
Generally healthy, and notably resistant to honey fungus. Alder Buckthorn is a host in the life cycle of crown rust fungus (Puccinia coronata), which affects some cereal crops, including oats and barley.
Its timber is brittle and hard (its genus name from the Latin frango, 'to break'), traditionally used for shoe lasts, wooden pegs and other low-value items, and its stems were favoured for charcoal used in gunpowder. It is still used to produce Swiss black powder for fireworks, fuses and military applications, and its straight shoots once made butchers' skewers. The bark yields a yellow dye. Many parts are poisonous yet long used in traditional medicine as a gentle laxative, best dried before use to avoid vomiting from anthraquinones.
