The catalpa tree, a distinctive ornamental shade tree, is a member of the Bignoniaceae family, known for its showy floral display and unusual, elongated fruit. This deciduous tree is recognized across North America by several common names, including Cigar Tree and Indian Bean Tree, due to its unique seed pods. The genus Catalpa is often planted for its aesthetic appeal and the generous shade it provides.
Identifying the Catalpa Tree
The most recognizable feature of the catalpa is its foliage, consisting of large, light-green leaves that are distinctly heart-shaped, sometimes reaching up to 12 inches in length. These leaves are arranged in whorls of three around the stem, a less common pattern among deciduous trees. The bark of a mature specimen is gray-brown and features prominent ridges and fissures.
In late spring to early summer, the tree produces clusters of trumpet-shaped flowers. These blooms are white with yellow streaks and purple or reddish-brown spotting inside the throat. Following the bloom, the tree develops its namesake fruit: long, thin seed pods that look like slender green beans or cigars. These pods mature to dark brown and often persist on the tree through the winter, making them a useful identification marker.
The two most common North American species are the Northern Catalpa (Catalpa speciosa) and the Southern Catalpa (Catalpa bignonioides). Northern Catalpa is the larger of the two, growing taller, and its flowers are more sparsely spotted with purple markings. The Southern Catalpa is a smaller tree with a denser floral display, and its blooms feature more prominent purple spots.
Growing and Maintaining Catalpa
Catalpa trees are known for their adaptability and resilience. They thrive best when planted in a location that receives full sun, though they can tolerate partial shade. While they prefer fertile, moist, well-drained soil, these trees can withstand a wide variety of conditions, including poor, sandy, or clay soils, and are tolerant of drought once they are established.
Young trees benefit from regular, deep watering until their root systems are fully developed. Pruning is necessary, especially when the tree is young, to establish a strong branch structure and a single, straight central trunk, known as a leader. Pruning should focus on removing suckers at the base and any dead, damaged, or crossing branches, and is best performed when the tree is dormant in late fall or early spring.
The tree is a fast grower, and its brittle wood and large leaves can sometimes lead to debris, especially after strong winds. While they are not heavy feeders, applying a balanced fertilizer in the spring can encourage healthy growth, particularly in less ideal soil types. Avoid excessive fertilization, which can lead to rapid, weak growth.
The Catalpa Tree’s Ecological Significance
The catalpa tree serves as the sole host plant for the Catalpa Sphinx Moth (Ceratomia catalpae). The larvae of this moth, commonly called the “Catalpa worm,” feed exclusively on the tree’s leaves and can sometimes completely defoliate a tree in a single season. Healthy trees recover quickly from this defoliation, often producing a second flush of leaves.
These caterpillars are highly valued by fishing enthusiasts, particularly in the Southern United States, as a prized bait for catching various fish species. This association is so strong that the Southern Catalpa is sometimes called the “Fish Bait Tree.” The catalpa worms also represent an important food source for birds and bats.
The wood of the catalpa tree is known for its rot-resistant properties. Historically, this durable wood was used for applications like fence posts, railroad ties, and furniture. The tree’s large canopy also provides significant shade, which is a major factor in its continued popularity as an ornamental and landscape tree.