This month there will be many showy white flowers on the small catalpa in front of the condos on Revere Road in the Parkwood subdivision in southern Durham. There are actually two very similar species, Catalpa bignonioides, the Southern catalpa, and C. speciosa, the Northern or hardy catalpa. Southern catalpas grow naturally in the Deep South while Northern Catalpas grow in the region where the Ohio joins the Mississippi. The Revere Road tree is probably a Southern catalpa. The species difference is dramatically revealed in spring, when they bloom at different times, but there are some other differences. Southern catalpa flowers have more spots and fewer blossoms per cluster. They also don’t grow as tall as Northern catalpas and there are differences in the seed pods and bark patterns. Apparently the crushed leaves of Southern catalpas have a bad smell. Northern catalpas might be the only ones that have glands at the base of the leaves, perhaps to attract ants for defense. Catalpas resemble royal paulownia, Chinese natives with big leaves and clusters of pale blue flowers in March or April, and have round seed pods. Catalpas are related to native crossvine and trumpet creeper. The word catalpa is supposed to be a native term for this tree while bignonioides refers to a vine with similar flowers and speciosa means ornamental.
Catalpas self-seed here, but are still pretty rare. The only other specimens I can think of are a few at Sedwick and Prospectus Drive, one on Grandale, one growing beside Northeast Creek near Jordan Lake, and several individuals of both species in Chapel Hill and Carrboro. There is a towering Northern catalpa across South Road from Coker Hall at UNC. A week ago it was crowned with white blooms and is probably peaking or past peak by now. There were one or two large catalpas near the corner of Fayetteville and 54, by Crooked Creek. Catalpas stick out because of their peculiar yellowish green leaves and pagodalike canopy. In their native habitat, catalpas grow near waterways and in bottomlands. They seem to prefer full sun, which could be a reason they aren’t more abundant here.
Catalpas were probably planted so widely for their flowers, and sometimes to grow caterpillars for fishing bait. Catalpa wood is sometimes used indoors, but is mainly used for posts, railroad ties, and telephone poles, because it is rot-resistant though brittle. Bark tea has been used as an antiseptic, laxative, sedative, and to treat snake bites and worms, while the pods were also thought to be sedative and to have an effect on the heart. The leaves were used to treat flesh wounds, as was seed tea, which was also used for respiratory problems. Catalpas are also sometimes called Indian cigars, which could be because kids smoked the pods
The flowers are grouped in panicles on the ends of new shoots. When they open, the large frilly white flowers are tubular and have five asymmetrical petals. They have dark purple spots and two yellow lines inside to guide pollinators. Bumblebees, honey bees, moths, butterflies, and ants are among the insects attracted by the nectar and pollen, yet one source says the nectar is toxic to skipper butterflies and ants. Catalpas will probably bloom for a few weeks, and then the trees sprout long, thin green pods all summer.
Catalpas are noticeable again in summer when they attract catalpa sphinx moths. Apparently their only larval food is catalpa, and the adults don’t eat. Like other sphinxes, catalpa sphinx caterpillars are hornworms, with a ‘horn’ on the tail, and they have striking yellow, black, and white stripes from head to tail. They are unusual for hornworms in being social during most of their caterpillar stage, and groups sometimes defoliate even a tree the size of the one in Parkwood. If Wikipedia is to be believed, cropdusting was first used against catalpa worms. When irritated they vomit a green liquid and thrash.
Nothing else seems to eat catalpa leaves much, so the trees are quiet until the brown pods attract angular gray leaf-footed bugs in late fall. As the weather gets cool, the pods split in half lengthwise, releasing winged seeds, while the husks remain on the trees into winter.