By Burt Glover
July 20, 2025

The Southern catalpa tree, Catalpa bignonioides, was once a common sight in southern yards. Native to the southeastern US, this old-fashioned favorite has something for every season — large panicles of exotic and delicately-scented flowers in the spring, followed in the summer with a generosity of cool shade from the tree’s oversized, heart-shaped leaves. In autumn, the leaves turn yellow, then fall to reveal the curious-looking seed pods that decorate the tree in the winter landscape. What’s not to love? 

Turns out, it’s the flowers, the leaves, and the seed pods that modern tastes so abhor. These are actually what earned its reputation as a “trash tree,” due to the tree’s habit of “littering” the ground year-round with spent flowers, brown seed pods and leaves as big as dinner plates. For people requiring a tidy, well-manicured landscape with not a leaf out of place, the catalpa is a nightmare. Some consider the tree invasive due to the prolific sprouting of seedlings from those brown pods. Worse still is the tree’s fast growth habit and easy-going nature, which makes it amenable to growing in a variety of soils and conditions. 

There was a time, though — especially during the days before air conditioning — when these fast-growing shade trees were considered indispensable. In the old mill villages of Aiken County, with many houses dating back to the 1870s, there is no shortage of catalpa trees. My own catalpa tree was not planted on purpose, however. It arrived by accident, the winged seed perhaps blown by wind and landing in no-man’s land — in that narrow strip of earth lying between the sidewalk and the busy road in front of my house.

When I took up residence in this house, the catalpa was already a small tree. It has never had an easy life. Seems that every time the tree sends out new growth toward the road, it is quickly “trimmed” by the large semis and cars passing by. A couple of years ago, it was even side-swiped by a hit-and-run that took my mailbox and part of the catalpa with it, the vehicle leaving in its wake a trail of broken truck fragments. By this point, my catalpa tree had to be about the sorriest, skinniest specimen in all of Aiken County. I couldn’t help but admire the tree and its tenacity to survive. I also wondered: what is the worst that could happen, now? I watched from my porch and sent it my well wishes. 

In a cruel answer to my question, Hurricane Helene hit. The storm left the catalpa undamaged; however, the giant oak tree in my front yard was not so fortunate. The cut-rate tree service I hired to remove the fallen oak piled the mess into that narrow strip of earth right next to the catalpa. When FEMA workers arrived to remove the storm debris from our area, the truck’s giant claw chewed out a 6-inch depth of soil at the base of the catalpa and, in the process, mangled and broke off some of the lower branches. I was not hopeful for its recovery.

This spring, I watched. I watched as those large, heart-shaped leaves appeared and grew to a profusion on the bare branches. My tree was back! That amazement was amplified when, in late spring, large clusters of flowers appeared in masses, up and down the tree — fragrant, trumpet-shaped blooms with creamy-white, papery petals and patterned purple dots and yellow spots on their insides. It was all too overwhelming. I watched as the bees and hummingbirds relished its flowers.

Catalpa flowers are followed by the long, green bean-like seed pods characteristic of the tree. Those pods eventually turn from green to brown, which earned catalpas two of its common names — bean tree and cigar tree.

ABOVE: Green catalpa “beans” which mature to cigar-brown in late summer.

As youngsters, my friends and I indulged in the fantasy of pretending to be proper barons of wealth with the pods, tho not actually lighting them up. As happened last year, I expected to see the spring flowers followed by green beans, then cigars. I was not prepared for what happened next.

At the start of July, my tree was green, healthy and surviving. Three days later, the tree was bare. No leaves, no green bean-like pods. Nothing but scraggly, bare branches. What happened?

I went out to investigate.

ABOVE: Catalpa caterpillars on a defoliated tree. Photos courtesy of the author.

The tree was full of caterpillars, who had reduced those enormous, heart-shaped leaves to a heavy scattering of caterpillar poop on the ground.  My hope for a flock of hungry birds to come and dispense with the caterpillars came and went. With nothing else to eat, the caterpillars dropped off to the steamy sidewalk below, squirmed a bit, and then crawled off.  I was sure that this was finally the death knell for my tree — but maybe not! 

I did a bit of reading and consulting with other local catalpa tree owners and learned that these fancifully-decorated yellow and black caterpillars, Ceratomia catalpae, are the “catalpa worms” I’ve heard about over the years. Serious southern fishermen actually plant groves of catalpas in their yard solely for the purpose of harvesting these ‘worms’ for fish bait. While catfish, bass and bream find the caterpillars irresistible, most birds do not. Apparently, a compound in the catalpa leaves renders the caterpillars distasteful to many birds. Not so for certain species of braconid wasps, which parasitize the developing caterpillars by laying eggs inside them. These wasps are probably the most effective predators for keeping the caterpillar populations in check. 

ABOVE: Catalpa caterpillars molt through multiple stages of growth, as seen in the various arrangements of dots, stripes and ikat patterns on this Graniteville, SC catalpa tree from a recent summer. Note the distinctive black “horn” at the end of abdomen. Photos courtesy of Wren Dexter, whose catalpa tree survived Hurricane Helene but was unfortunately destroyed during the removal of large, damaged trees nearby.

Having solved that mystery, I wondered where the caterpillars had crawled off to after defoliating the tree and thumping down onto the sidewalk. It turns out that those caterpillars were looking for a nice soft spot in the soil to dig into the ground, where they will pupate over the winter. In spring, they will emerge as catalpa sphinx moths — large, gray moths with a wingspan of 3” that will take to the night air and be drawn back to the catalpa tree to repeat the life cycle.

The male catalpa moth, Ceratomia catalpae. Image shared via Wikipedia Creative Commons license. Muséum de Toulouse, CC BY-SA 4.0.

Like so many flowers pollinated by moths, Catalpa flowers draw night pollinators with their white coloration and enhanced night-time scent and nectar production. After feeding, the female moths mate, then lay hundreds or thousands of eggs on the tree, from which hordes of hungry caterpillars will emerge to devour the leaves and, in some cases, completely defoliate the tree.

The good news is that catalpa trees have somehow adapted to this. In the probable 60 million years of coevolution between moth and catalpa, the two species have apparently reconciled some benefit to the occasional destruction. Healthy trees have been known to survive repeated defoliations in a season. Catalpas may be the only tree that can do this. Interestingly, not all catalpa trees play host to the caterpillars. Also, some trees play host every year, while others do it only some years. It seems the more I learn about the catalpa trees, the more questions I have.

One unexpected find in my reading was the news that the Southern catalpa is falling back into favor, due in part to the greater understanding of the integral role of native plants in a healthy ecosystem. Perhaps future generations will find, as past generations knew, that the “littering” of leaves and flowers (compost!) is a small price to pay for a tree’s beauty, its shade value, and importantly, those catalpa worms that arrive just in time for the June fishing season. 

Catalpa wood was also valued as a rot-resistant option for making fences and posts, and has a long tradition in furniture-making, wood turning and musical instruments, notably guitars. The wood is said to be lightweight, easy to work with, and carries a beautiful tone.

For earlier generations that drew their subsistence from the land — through home gardens, a backyard flock of hens and a bounty of bream, bass and catfish from the local fishing hole — a bucket of catalpa worms was a princely gift. It’s all a matter of perspective.

Speaking of which, here it is July 20, and, much to my amazement, new leaves have already appeared on the denuded tree. If not for my story, you’d never know the tree had suffered such an assault less than three weeks ago.

ABOVE: My catalpa tree, recovered in less than three weeks!

Given its location, my catalpa will most likely continue to live a hard-scrabble existence and will never grow to be a grand, centuries-old specimen, (see photo below), but the tree is nonetheless part of a functioning ecosystem, providing food and shelter for other native species. For my part, I will be watching from my porch and, as always, hoping for the best. I do love that tree.    

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Contributor Burt Glover became an accidental naturalist during his earliest childhood days exploring the dirt roads, backyards, polo field and barns of the Magnolia-Knox-Mead neighborhood of 1950s Aiken. Birds are his first love, and he can identify an impressive range by song alone. He asserts that he is an observer, not an expert, on the topics of his writings, which range from birds, box turtles, frogs and foraging, to wasps, weeds, weather and beyond.

An old Catalpa bignioides said to be 200 years old.
Photograph from Dreamstime. Photographer: Gunold.