Erythrina crista-galli is a small tree, the girth of its trunk measuring 50 cm (20 in). Normally it grows 5–8 m (16–26 ft) tall, although some individuals, such as in the Argentine provinces of Salta, Jujuy and Tucumán, can grow up to 10 m (33 ft). The root is a taproot with nodules produced by nitrogen-fixing bacteria. The bacteria live in symbiosis with the tree, facilitating the tree's absorption of nitrogen in return for organic substances which the bacteria need. The tree's trunk is woody with irregular, spiny branches. These branches form a layer without definite form and die after flowering.
Invasive in eastern Australia.