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Rhamnus

Family

Rhamnaceae

Common names

Buckthorn

There are few groups of trees and shrubs comprising so many hardy species as Rhamnus that possess so little garden value. They have scarcely any beauty of flower, the blossoms being small, and either green, yellowish green, or brownish. The fruits are more attractive, being often very abundant and reddish when approaching ripeness. When fully ripe they are usually black or very dark purple.

The genus contains about 160 species of evergreen or deciduous trees and shrubs, the hardy ones widely spread over northern temperate latitudes. The leaves are normally alternate, but occasionally opposite; the flowers perfect or unisexual, with the sexes on the same or separate trees. Flowers with a four- or five-lobed calyx and the same number of petals and stamens; petals sometimes absent. Fruit a drupe, roundish or top-shaped, usually from 16 to 13 in. in diameter, enclosing two to four seeds.

The genus is divided as follows:

subgenus rhamnus. – Winter-buds protected by scales. Flowers usually tetramerous, unisexual, with three or four styles.

subgenus frangula. – Winter-buds naked. Flowers usually pentamerous, hermaphrodite, with a single style. Here belong (of the species treated below): R. californica, R. caroliniana, R. frangula, R. latifolia, R. purshiana, and R. rupestris. This subgenus is sometimes separated from Rhamnus as the genus Frangula.

Useful characters for identifying the species are: the number of veins of the leaf, and whether they are parallel or converging; the absence or presence of marginal teeth; the arrangement of the flowers – whether in stalked or stalkless clusters; and the presence or absence of spines at the tips of the side twigs. Various members of the genus yield yellow or green dyes, and most of them have laxative or purgative properties in bark and fruit.

They are easily cultivated in any ordinary soil. Some do not strike root readily from cuttings, but can be layered; seeds afford the best means of propagation when obtainable. The best species for gardens are: R. alaternus, as a dense evergreen; R. fallax and R. imeretina, for fine foliage; R. pumila and R. rupestris, as dwarf shrubs; and R. purshiana, for its medicinal interest and as a handsome tree.

The gender of Rhamnus is a matter for dispute. The name derives from the Greek rhamnos, which is feminine and was taken unchanged into Latin. But the early botanists latinised the name to Rhamnus and treated it as masculine.

Species articles