acacia

Thorn trees with Mount Kilimanjaro in the background, in Tanzania. Thorn trees, of the genus Acacia, are an important component of the plant life of the dry, subtropical African savannah.

Any of a large group of shrubs and trees that includes the thorn trees of the African savannah and the gum arabic tree (Acacia senegal) of North Africa, and several North American species of the southwestern USA and Mexico. The hardy tree commonly known as acacia is the false acacia (Robinia pseudacacia, of the subfamily Papilionoideae). True acacias are found in warm regions of the world, particularly Australia. (Genus Acacia, family Leguminosae.)

A. dealbata is grown in the open air in some parts of France and the warmer European countries, and is remarkable for its clusters of fluffy, scented yellow flowers, sold by florists as mimosa. The leaves of the genus are normally bipinnate (leaflets on both sides of each stem and stems growing on both sides of a larger stem), and the flowers grow in a head.

In America the fruits of the edible acacia are used as food; in the islands of Mauritius and Réunion the leaves of A. lebbek serve as soap. A. arabica is used in tanning and gives gum arabic, while gum senegal comes from A. senegal. The drug catechu is prepared from A. catechu.