The northern catalpas are blooming in Columbia this week. Natives of the mid Mississippi Valley, these trees are planted widely as ornamentals, primarily due to their showy, white flower clusters that appear in late spring. Rapid growers, northern catalpas may reach 100 feet or more and are easily recognized by their large, heart-shaped leaves. While they favor moist, well drained soil, they adapt to a wide range of soil conditions; in fact, we have a large catalpa on our farm in Colorado.
Southern catalpas, native to the Gulf Coast region, are smaller, topping out at 50 feet or so. Both species, though not in the legume family, produce long, narrow seed pods (up to 20 inches long) and have been known as Indian bean trees. Their wood, soft and brittle, is tolerant of moisture and has long been used for fencing and railroad ties; other uses include the manufacture of frames, furniture and bowls.
Catalpa worms, larvae of the catalpa sphinx moth, are the primary natural enemies of these trees. After overwintering in the soil as pupae, the moth emerges in spring and females deposit their eggs on the new vegetation. Caterpillars hatch by mid May and begin devouring the large leaves of the catalpa. Fortunately, for the trees, birds (such as cuckoos) are around to feast on the larvae and humans have discovered that catalpa worms are prime fish bait.
