Southern Catalpa

Catalpa bignonioides is native to the southeastern United States, with a natural range centered in Alabama, Mississippi, Georgia, and northern Florida.

• Native to floodplain forests, stream banks, and moist woodland edges in the Gulf Coast states
• Also found in scattered populations in Tennessee, the Carolinas, Louisiana, and Arkansas
• Occurs at elevations from sea level to approximately 300 meters
• Has been widely planted throughout the United States and Europe as an ornamental since the 18th century
• Naturalized in many areas beyond its native range, particularly in the Midwest and Mid-Atlantic states
• First described scientifically by Thomas Walter in 1788
• The closely related Northern Catalpa (Catalpa speciosa) is native to the Mississippi River valley and has a similar appearance
• The two species are often confused in cultivation, but C. bignonioides has smaller leaves, flowers with more purple spotting, and a more spreading habit
• Indigenous peoples of the Southeast used Catalpa wood and bark for various purposes
• The tree was introduced to Europe in the 1720s and became a popular ornamental in English gardens
• Thomas Jefferson planted Catalpa trees at Monticello

Catalpa bignonioides is a medium-sized, broadly spreading deciduous tree with a distinctive rounded crown.

Size and habit:
• Typically grows 10 to 18 meters tall with a spread of 8 to 15 meters
• Crown is densely rounded, almost as wide as tall, with a picturesque, irregular outline
• Trunk is short, 30 to 70 cm in diameter, with thin, brownish-gray bark that develops scaly ridges
• Branches are spreading, somewhat pendulous, creating a dome-like canopy

Leaves:
• Enormous, simple, heart-shaped (cordate), 15 to 25 cm long and 10 to 20 cm wide
• Bright light green above, slightly paler and downy below
• Leaves are borne in whorls of three at each node — a distinctive arrangement
• Margins are smooth to slightly wavy
• Leaves emerge late in spring and drop early in fall
• When crushed, leaves have a characteristic faint, unpleasant odor

Flowers:
• Large, showy, white, trumpet-shaped, 3 to 5 cm across
• Produced in large, upright, branched panicles 15 to 25 cm tall
• Each flower has ruffled, crinkled petal edges and purple-orange spots and stripes inside the throat
• Two large, pale yellow blotches mark the lower lip
• Blooming occurs in late spring to early summer, creating a spectacular display
• Flowers are fragrant and attractive to bees, butterflies, and hummingbirds

Fruit:
• Long, narrow, cylindrical pods 15 to 40 cm long and 0.5 to 1 cm in diameter
• Green when immature, turning dark brown to black when mature
• Pods split open in fall, releasing numerous flat, fringed (winged) seeds
• Pods persist on the tree through winter, creating a distinctive silhouette

Catalpa bignonioides plays an interesting ecological role centered on its relationship with the Catalpa Sphinx caterpillar.

Habitat:
• Native to floodplain forests, stream banks, and moist woodland edges in the southeastern US
• Adaptable to a wide range of conditions including urban environments
• Tolerates wet, compacted, and alkaline soils

Ecological role:
• Exclusive host plant for the Catalpa Sphinx caterpillar (Ceratomia catalpae) — the caterpillars can defoliate entire trees in some years
• The Catalpa Sphinx caterpillar is one of the most popular live fishing baits in the American South, known as "Catalpa worms"
• Flowers are pollinated by bees, butterflies, and hummingbirds
• Seeds are eaten by birds and small mammals
• Large leaves provide dense shade and abundant leaf litter
• Dead, hollow trunks provide nesting sites for birds and shelter for bats
• The tree is relatively short-lived, typically surviving 50 to 70 years
• Adapts well to disturbed sites and urban environments
• Can naturalize beyond its native range in suitable habitats

Planting:
• Propagation from seed or cuttings
• Seeds require cold stratification for 2 to 3 months, or can be fall-sown outdoors
• Germination occurs in 2 to 4 weeks after stratification
• Root cuttings and softwood cuttings in summer root readily
• Fast-growing, especially in youth
• Plant in full sun to partial shade
• Adaptable to a wide range of soils including clay, loam, and sandy soils
• Prefers moist, well-drained soil but tolerates wet and compacted conditions
• Hardy in USDA zones 5 to 9
• Drought-tolerant once established
• Minimal pruning required — natural shape is attractive
• Relatively pest-free except for Catalpa Sphinx caterpillars, which can be controlled if desired (or encouraged for fishing bait)
• Verticillium wilt can be a problem in some regions
• Branches are somewhat brittle — may suffer breakage in ice storms or high winds
• Best used as a specimen tree in parks, large gardens, and naturalized areas
• Not ideal for formal landscapes due to coarse texture and somewhat unkempt appearance in winter

Uses:
• Primarily an ornamental shade tree — valued for enormous leaves, showy flowers, and distinctive winter silhouette with hanging pods
• Catalpa Sphinx caterpillars are among the most prized fishing baits in the American South — fishermen deliberately plant Catalpa trees to attract them
• Wood is soft, lightweight, straight-grained, and rot-resistant — used for fence posts, railroad ties, and utility poles
• Historically used for making coffins due to durability and workability
• Wood is used for carving and making rustic furniture
• Bark and pods have been used in traditional medicine as a mild sedative, antispasmodic, and treatment for asthma and whooping cough
• Flowers produce nectar for bees — catalpa honey is a minor regional specialty
• Planted as a shade tree for livestock in pastures
• Used in mine reclamation and erosion control due to adaptability and fast growth
• An excellent tree for large parks and public spaces where its bold, tropical-looking foliage creates dramatic effect
• The unusual seed pods are used in dried flower arrangements and crafts