CATALPA

I have often seen and heard catalpa referred to as a trash species, to be avoided. I disagree! Catalpa speciosa (northern catalpa) is a wonderful plant -- one of my favs -- although I know many people will think me crazy for saying so. After taking in this post, you may want to reconsider, perhaps even change your mind. All plants have some sort of potential negative issue, usually more of a problem we created by not understanding and using the taxon appropriately.

Northern catalpa (C. speciosa) is a medium to large deciduous tree originally native to a narrow zone along the Ohio and Mississippi rivers near their juncture. It has naturalized throughout much of the eastern U.S. and parts of Ontario. The genus is based on the Cherokee name for the plant (catawba), while the species means showy. Catalpa, like crossvine and trumpet vine, is a member of the Bignoniaceae, a primarily woody tropical family noted for impressive flowers. Catalpa is easily grown but shade intolerant, maturing into a tree that rarely exceeds 75 feet tall and generally is about twice as tall as wide, with lower limbs sometimes arching to elbow the ground. The top pic above is of a 4 feet tall one-inch caliper container specimen one decade after planting (15-inch DBH and 25 feet tall as of 2024) with many lower branches removed as the tree grew to (1) allow easy access underneath and (2) to prevent damming since the small stream in the foreground frequently floods. Note the abundance of browned shriveled interior leaves (pic taken in early October at the end of an extended dry period).

Northern catalpa's leaves are simple, large (to one foot diameter) and heart-shaped. The leaves turn yellow in fall assuming they do not get zapped by an early freeze and then abruptly forced to drop. Regardless, like ginkgo, the leaves mostly fall off in a single day. The flower buds are plump, burgundy, and remind me of tiny pomegranates. The flowers, which open in central Indiana the first week or so of June, are large, bell-shaped, zygomorphic and abundant. I have heard some refer to them as orchid-like.  Each flower is white with purple and yellow inner spotting (see pic above) and they are displayed in large trusses. The individual flowers are sightly fragrant but, when in full bloom, can be impressively so in mass. Anthesis lasts about two weeks. Catalpa is one of the last trees to throw leaves in spring owing to the family's tropical heritage. Curiously, and unlike most other trees species in the Midwest, the leaves have a whorled arrangement, typically three per node. The leaf scars are sunken and distinctive, resembling suction cups. Catalpa is a fast-growing species that tends to grow crooked. Asymmetric form (contorted and/or weeping) bothers some people, whereas I find that wild look mystically beautiful. Anthropomorphic is an apt descriptor for old catalpa specimens, seeming to be directly from the world of Harry Potter. Furthermore, catalpa is as appealing when leafless, sometimes even more so.

Catalpa is also called worm or bait tree because the large catalpa (sphinx) moth caterpillar (a hornworm up to three inches long, see pic above) which feeds only on catalpa leaves (monophagous). The caterpillars presence is not a given but they can be numerous. They unnerve many people but, contrary to the claim, the horn of this species is not venomous (i.e., harmful to humans). I recall harvesting the "worms" for fish bait from a tree in my paternal grandparent's side yard when I was a boy in south central Illinois, taking care not to squish them when collecting. The appropriate word is YUCKY! The "cats" are perfect for bass. One will occasionally find a lighter colored form of the caterpillar. Regardless of color form, one commonly finds the "worms" with white, elongate, fuzzy protruding outgrowths -- pupating cocoons of an endoparasitoid wasp. The larvae literally feed on the caterpillar from within.

Catalpa is well-suited for urban landscaping but should be given adequate space -- not up against a building or other structure. Catalpa wood is weak, light weight, with low shrinkage but (surprisingly) is very decay resistant -- formerly much used for fenceposts. Give the plant adequate space. I suggest a circle of at least 750 square feet (30+ ft diameter). And don't forget, full sun. The species is reasonably long-lived (occasionally a century or more) and is even more enchanting as it ages. Older specimens are often fabulous with branches that commonly are arched and/or twisted with the trunk often forming strange irregularities and bark plates, or seemingly bark less. The bark on younger specimens is more likely ridged. The massive 5+ ft DBH specimen pictured above, from Clay City, IL (Oct 2021) was "mature" when I was a youngster. I'm now approaching 73. The trunk reminds me of an alien sea creature. The national record northern catalpa specimen was in Indiana -- its DBH nearly 8 feet! The bottom pic above is a specimen with about the same diameter, located in Ohio about an hour east of Cincinnati and may be the actual current national record specimen. In terms of OH MY factor, catalpa has few rivals -- worthing of praise and appreciative gawking. Every old specimen is noticeably different and outstanding is common. A roadway or lane lined with stately older specimens is a sight to behold. The problem with getting that outcome often is the lack of foresight/planning, not permitting adequate space for the tree(s) to age. ALL woody plants have indeterminate growth. Again, as I point out in my lectures, the gardening fault (the problem) often lies with the planter (his/her choices) not the plant.

As noted earlier, Catalpa has a bad reputation. Many people despise catalpa trees because they are messy -- the shed large leaves, long thin fruit as well as the snowstorm of spent flowers, looking as if a giant bag of popcorn was spilled. The flowers wither to brown. The catalpa fruit, which can be up to 24 inches long, but only 1/2 inch thick, resemble a bean pod and are the basis for the name cigar tree. The fruit starts out green and matures to brown. A capsule, it dehisces to expose, thus freeing, small, winged seeds (several thousand per pod).  In fact, some people call it the green bean tree. Catalpa is easily grown from seed, with germination improved by stratification.  Catawba prefers a wet to medium wet loamy soil but will tolerate dry sites as well as clayey soil. Wild growing (naturalized) seedlings are not uncommon, but catalpa is nowhere near weedy.

Be aware that catalpa has a substantial tap root as well as well-developed lateral rooting. If trying to procure a specimen from the wild choose a small one (no more than a foot or two tall) to reduce the likelihood of root damage during the removal digging. Rapid growth will quickly overcome the small initial size. -- I find it amazing that despite possessing enticing characteristics (morphology and behavior) the wild form of catalpa is as good as a purchased garden center specimen, if you can find one -- uncommon because of the plant's reputation.

The similar looking, but not as big, southern catalpa (C. bignonioides) produces fewer but larger flowers, has slightly broader and shorter seed pods and its leaves are foul smelling when bruised/crushed. Southern catalpa apparently had a restricted native range (southern U.S., Louisiana to SW Georgia) and is less commonly used as an ornamental. However, it is now more widely distributed and is capable of being grown wherever northern catalpa is hardy. The cultivar 'Nana' is a dwarf that usually is grafted onto rootstalk of a normal southern catalpa. While novel, I find 'Nana' much less interesting since it almost never produces flowers, nor do I like the manicured look, too formal -- essentially a lollipop in the landscape. On the other hand, I find the semidwarf 'Aurea' captivating. As the name implies, 'Aurea' produces golden-yellow leaves that green a bit by midsummer but (unlike 'Nana') 'Aurea' does produce flowers. The problem is finding a specimen -- likely procured only online as I have never seen it offered at a garden center or nursery despite the fact 'Aurea' is a stunning plant. The smaller stature is likely from reduced chlorophyll and rootstalk induced dwarfism.

I also have some experience with the purple or purple leaf catalpa (C. x erubescens 'Purpurea' - bignonioides x ovata). The leaves (especially the new spring growth) and the flowers are quite appealing, but the main corpus of the tree does not seem to develop the same wonderful, contorted form -- time will tell.

I recall only once ever seeing a catalpa with noticeable storm/wind damage. It could be the form; the fact catalpa specimens are never towering (rarely over 60 ft tall) thus escape the worst of the force. It could be that, despite being observant, I simply have not been in the right place at the right time, around enough specimens since, like magnolia, catalpa is NOT a climbing tree (i.e., susceptible to snapping). But it could also be at least partially attributable to the fact that old specimens commonly/naturally look disarranged thus it could be difficult to tell the difference because the damage is masked. My guess is that the contortion commonly on display in the branching and trunk also strengthens the plant internally (the wood) by cellular configuration, combined with the wood's low density, thus making catalpa less likely to tear away (split) than a straight grained species. It could also be due to constant tending by dryads. Truth be told, I am good buddies with two dryads -- who provide me with lots of good plant/nature insight -- but for security reasons they have asked me not to divulge more about them, not even their names. Since they scare me, and are likely illegals, I will comply :) -- A good story does not the truth make; our gullible nature has been a recurring theme in my rants. We need to ask WHY / REALLY? more often.

I will finish by challenging you to be more observant and less hidebound. Try to appreciate species as awesome as catalpa when you are out and about or choosing your garden residents rather than blindly falling for and selecting the standard fare garden centers foist upon us (e.g., ubiquitous and plain red maples, honey locust, et al). You should also be more careful about who and from where you accept advice. Be very discriminating and understand this, the standard garden centers offer mostly pedestrian plants because that's what most people (sheeple) think they should like (mimetic desire), and will buy, often then situating their "likely less than the best choice" poorly. Unfortunately, we are not a gardening society while also mostly stubborn and reluctant, if not outrightly afraid, of different and change. Now gaze at the above pics and try to convince yourself catalpa isn't impressive and worthy, if the appropriate conditions exist.