acacia

Acacia is a genus of flowering plants in the legume family (Fabaceae) that includes trees and shrubs. It comprises more than 1,000 species, with high diversity in Australia and Africa and representatives in other continents. Taxonomic revisions in some classifications have moved many species to Vachellia and Senegalia, but the name Acacia remains widely used in horticulture and industry. The name is commonly linked to Greek akis, meaning thorn, reflecting many spiny forms.

Characteristically, Acacia species exhibit a range of leaf forms. Some have true bipinnate leaves; many Australian species instead bear phyllodes, flattened leaf stalks that perform photosynthesis. Thorns or spines are common on older branches, though some species are spineless. Inflorescences are typically yellow or cream and appear as spherical heads or elongated spikes. Fruits are pod-like and contain several seeds.

Ecologically, acacias are adapted to warm, often dry habitats and poor soils. They frequently form symbiotic relationships with nitrogen-fixing bacteria in root nodules, contributing to soil enrichment. They attract pollinators and provide shelter for insects, birds, and other animals; their dense canopies and rapid growth can influence savanna and woodland structure.

Uses include the production of gum arabic, harvested mainly from Acacia senegal and Acacia seyal, used as a stabilizer in foods and beverages and in pharmaceuticals. Wood, tannins from bark, and ornamental plantings are other important values. Some species yield edible flowers or nectar, and bees produce Acacia honey from their blossoms.

In some regions, several Acacia species have become invasive when introduced outside their native ranges, altering local ecosystems and outcompeting native vegetation. Management typically involves containment, restoration, and, where appropriate, mechanical or ecological controls.