Buckthorn, European, Rhamnus cathartica

Life Cycle

Perennial.

Propagation

Reproducing only by seed. Grows as a bushy small tree or several-stemmed shrub up to 6 m high.

Stems

Most branches older than one year are tipped with a short, sharp thorn, (hence "thorn" in its English name); this thorn often present in the fork of 2 branches.

Leaves

Leaves usually opposite (2 per node), but sometimes alternate (1 per node), elliptic or oblong usually with fine rounded teeth but sometimes nearly smooth, dark green above and lighter green or yellowish-green below; usually with 3 main branching veins (sometimes 2 or 4) on each side of the midrib that strongly curve or arch forward towards the tip of the leaf.

Flowers and Fruit

Flowers small, with 4 sepals and 4 petals, greenish to yellowish, short-stalked, in small clusters from the axils of leaves or on short twigs along the stem; each flower unisexual with either 4 stamens or 1 pistil but not both, and the sexes usually on different plants; berries round, 5 - 6 mm in diameter, purplish-black and very juicy with 4 very hard seeds (stones). Flowers during May and June but the berries, and often the dry leaves, persist on the tree long into winter.

Habitat

European buckthorn was introduced as an ornamental shrub, but its seeds have been widely scattered by birds and other animals so it is common in fence lines, woodland, pastures and abandoned farmyards throughout southern Ontario.

Distinguishing Features

It is distinguished by the sharp, thorn-tipped branches in contrast to the simple or compound thorns growing from the sides of branches in the Hawthorns, by the prominent forward-curved side veins of the leaves, the clusters of purplish-black berries along the stems and short twigs, and each berry usually with 4 hard seeds.

Toxicity

Because European buckthorn is an alternate host for the fungus which causes leaf and crown rust of oats, it must be destroyed to minimize this disease on oats. The juicy berries are very bitter and cathartic, and usually cause severe stomach cramps if eaten.

Legislation

Noxious under the Ontario Weed Control Act.


Figure #1.

European buckthorn.


Figure #2.


Figure #3.


Figure #4.


Figure #5.

Sharp thorn on tip of branch.


Figure #6.


Figure #8.

Branch in November, Southern Ontario.