1. Catalpa bignonioides Walter (southern catalpa, common catalpa)

Pl. 304 e; Map 1282

Plants trees to 15 m tall. Bark light brown, divided into thin, scaly plates on older trunks. Leaf blades 8–22 cm long, entire or less commonly shallowly 3-lobed or 3-angled toward the base, narrowed or short-tapered at the tip, the upper surface glabrous, the undersurface persistently pubescent with short, curly, unbranched to stellate hairs, especially along the veins. Calyces 9–12 mm long. Corollas 2.5–4.0 cm long, white, the middle lobe of the lower lip not notched. Fruits 20–45 cm long, 0.6–1.0 cm in diameter, relatively thin-walled, the valves becoming flattened after dehiscence. Seeds with the body 12–16 mm long, 2.5–4.5 mm wide, the hairs of the tufts converging to a more or less pointed tip. 2n=40. May–June.

Introduced, widely scattered in southern and central Missouri (native of the southeastern U.S. from Florida to Texas; introduced farther north). Margins of streams and rivers; also roadsides, railroads, and moist, disturbed areas.

The two North American catalpas can be difficult to distinguish. In addition to the key characters separating them, C. bignonioides tends to be a somewhat smaller tree, with more numerous, slightly smaller flowers per inflorescence than C. speciosa. Also, the corollas have a denser pattern of lines and spots in the throat, and the leaves have a strong unpleasant odor when crushed or bruised, whereas those of C. speciosa are less strongly and more pleasantly scented.