Erythrina crista-galli is a small tree, the girth of its trunk measuring 50 cm. Normally it grows 5–8 m tall. 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. The tree flowers in the summer. The red flower, arranged in inflorescences of the raceme type, is pentameric, complete, and of bilateral symmetry. The flowers are rich in nectar and are visited by insects, which usually have to crawl underneath the carina and thus pollinate the flowers. The tree's fruit is a legume, a dry pod a few centimeters in length derived from a single carpel and contains about 8-10 chestnut-brown bean-shaped seeds.