Tree of the Week: Catalpa (Catalpa bignonioides)

Less than a month ago we were admiring the pretty white flowers of the catalpa trees (Catalpa bignonioides). Of the two individuals in the arboretum collection, we focused on the the larger individual for our tree of the week post. The smaller tree also had flowers at the time, and, today, both trees have the conspicuous 'Indian cigars,' or bean pods, hanging from their branches. This week we have photos of the smaller catalpa specimen. It is of special interest because it is playing host to the famous 'catawba worm'.

This catalpa is less than 5 years old. It germinated in the campus greenhouse from seeds collected at an old homestead outside Springhill, Louisiana. In 2015, it was planted in the arboretum, at the bottom of a steep slope near the Fitness Center.

The long, slender catalpa fruits are already noticeable, hanging from the branches.

The seedpods are very long, measuring approximately 16 inches. The fruits aren't ripe yet; they will most likely increase in length.

Catalpa leaves are large and heart-shaped. The leaf and the petiole measure over a foot in length.

The underside is light-green and fuzzy.

Some of the leaves have lost there heart shape. The tip of this leaf has been eaten by the catalpa 'catawba' (or even "catawbla") worm (Ceratomia catalpae), who is pictured inching along the leaf midrib.

The caterpillar is greenish-white to yellowish-white with a black head, black spots, and a black spike on the rump. It measures over an inch in length. These worms have a reputation for being a high quality fish bait.

There is variation among the caterpillars: some are more black than white, and their appearance also changes as they grow larger.

We aren't seeing too many caterpillars yet; only a few leaves have been eaten. But these catalpa worms are known to entirely defoliate their hosts, sometimes more than twice a season. If defoliation does occur, new leaves are expected to develop quickly.

For more information about this species consult the following:
United State Department of Agriculture - be sure to zoom in on the distribution map
Auburn University has an informative article about the catalpa worm. You can find it here.