CATALPA WORMS eat only catalpa foliage and do not kill the trees.

Catalpa worms get their name from the catalpa tree that they host on.

There are two native species of catalpa in America, Catalpa bignoniodes (southern catalpa) and Catalpa speciosa (northern catalpa). Both are common in Texas. Northern catalpas make tall trees with straight trunks and are just finishing blooming while southern catalpas are more spreading with multiple branched trunks and bloom several weeks later.

Although they are not popular in modern landscapes or the nursery trade, they were once commonly planted for fence posts, their showy flowers and their fishing worms. Both species are fairly prized in Europe, with beautiful specimens in all the fine botanical gardens.

Although considered a bit “trashy” in the U.S., I’ve always enjoyed and admired them. Catalpa, along with Sassafras, are the two native trees that kept their American Indian names for their Latin names. Among country folks you also hear the catalpa referred to as the Catawba tree or catawbie tree, while in books you’ll also see it called Indian bean for its long beans.

I’m often asked if the worms will kill the trees. The answer is no. Catalpa worms are the larva of the catalpa sphinx moth. They feed on nothing in the world but catalpa foliage. The moths are attracted to the trees, pollinate the flowers and lay their eggs on the underside of the foliage. The two have evolved together. The pollinated flowers help the tree set seed to spread the species around while the caterpillars gain toxic alkaloids from the leaves to make them distasteful to the birds. After eating their fill of leaves, they then drop to the ground, pupate and ultimately re-emerge as moths. The trees always sprout new foliage with as many as two to three defoliations per season. It wouldn’t make sense for the worms to kill the trees, as they require them for their survival.

Catalpas make large bold trees in the landscape, with huge trunks as they age. The state champion northern catalpa has a trunk diameter of 268 inches, while the champion southern catalpa sports a girth of 265 inches.

In East Texas I’ve actually seen a few catalpa “orchards” where the trees are topped annually, making worm-harvesting easier. I once saw one where the trees weren’t topped but had inverted tin cones around the trunks to trap the worms on their way down. In East Texas, folks are serious about fishing!

Although they are often maligned, or forgotten about entirely, catalpas are interesting natives with a fascinating story.

Greg Grant is the Smith County horticulturist for the Texas A&M AgriLife Extension Service. You can follow him on Facebook at Greg Grant Gardens, read his “Greg’s Ramblings” blog at arborgate.com or read his “In Greg’s Garden” in each issue of Texas Gardener magazine (texasgardener.com). More gardening information from the Texas A&M AgriLife Extension Service can be found at aggie-horticulture.tamu.edu.