Acacia

Acacia is a group of flowering trees and shrubs in the legume family, Fabaceae. The name covers hundreds of species, especially in Australia, where acacias grow in dry forests, woodlands and open landscapes. Many acacias have small flowers gathered into dense balls or spikes, followed by seed pods.

In several Australian species, the true leaves are greatly reduced and green, flattened stems called phyllodes carry out photosynthesis instead. This adaptation can reduce water loss in hot, dry climates. Acacias are important members of their ecosystems.

Their roots can live in partnership with soil bacteria called rhizobia, which convert atmospheric nitrogen into forms the plant can use; in return, the bacteria receive nutrients and shelter. This process can enrich nitrogen-poor soils. Flowers provide food for insects and other pollinators, while seeds and foliage are eaten by various animals.

Some species have sharp spines, and some have relationships with ants that protect the plant in exchange for food or shelter. Acacias are also cultivated for shade, timber, fuel, soil restoration and ornamental planting. However, a useful species can become invasive when introduced elsewhere, so planting should consider local ecological risks.