The Southern Catalpa tree (Catalpa bignonioides) is easy to recognize because of its very large leaves, its beautiful mid-summer flowers and its extremely long slender fruits that persist from late summer through the winter.
It is called “southern” because it is native to the southeast United States (Florida, Georgia, Alabama and Mississippi) where it also is called the Catawba tree. However, it can withstand frost and is fairly hardy (wet or dry soils, sun or shade) and so has naturalized widely (USDA Hardiness zones 5-9). The Catalpa is liked for its shade and mid-summer flowers and disliked because it drops a huge flower load in the late summer, big leaves that are hard to rake in the fall and tons of seedpods in the late winter and early spring. The naturalists among us love it because it is such an interesting tree!
The Catalpa is a deciduous tree that reaches anywhere from 25 to 60 feet at maturity. There is a specimen in Mississippi that reached 88 feet. The crown is often forked which may account for its name. Catalpa is derived from the Muscogee word for the tree “kutuhlpa” which means “winged head.” At maturity, the grey-brown bark has irregular ridges with reddish brown scales.
The heart-shaped leaves are very large, 5-12 inches long and 4-6 inches wide, with a long petiole (stem). Another interesting characteristic of these leaves is that they secrete nectar from their undersides which is unusual for leaves. This nectar plus that from the flowers attract honeybees that are necessary for catalpa pollination. The leaves also are the sole food source for the larvae (caterpillars) of the Catalpa sphinx moth (Ceratomia catalpa). When caterpillars are numerous, they can defoliate the entire tree. Damaged leaves secrete more nectar. The increased nectar secretion attracts predatory insects such as ants and ladybird beetles that then attack or remove the eggs and larvae of the catalpa sphinx moth. Thus, both the tree and the insects benefit from the increased nectar secretion. Sometimes the trees are planted just to harvest the caterpillars which make great catfish bait, resulting in another name for the tree: the fish bait tree.
The flowers appear in mid-summer in clusters at the ends of stems. They have been described as orchid-like or iris-like. The individual flowers are white, trumpet-shaped, 1 to 1.5 inches across and have yellow and purple markings inside. They make for a very attractive display when other trees are not in bloom. The seed pods (fruits) are long (10-24 inches), green and slender during the summer, resembling greatly elongated green beans. They are the reason the tree is also known as the Indian Bean Tree, supposedly called that because they were seen growing in fields of the Cherokee. The seed pods are not edible, however. The fruits mature in the fall and turn brown. Seeds are released when they split longitudinally. Winds often blow the pods off the tree.
I hope you agree that this a very interesting tree!