The showy northern catalpa

American Forests, Summer, 2005 by Meghan Amoroso

Walking along a river's bend your eye is drawn to a rather large tree with showy white flowers. Look closer, and you can see a fisherman attempting to shake caterpillars off its leaves.

Fishermen are particularly fond of this tree, which hosts the catalpa sphinx caterpillar, popular as fish bait since the 1870s. This is the northern catalpa (Catalpa speciosa), a native to the central Mississippi River Valley but found in 17 states across the U.S. and in southern Canada.

Not going fishing anytime soon? You can see these trees in the city, planted for their aesthetic beauty. Landscapers use the trees in lawns or parks because of their striking long seedpods in winter and bold springtime flowers.

A genus of 11 species of deciduous trees, the catalpa is found near riverbanks and in the woodlands of China and North America. The Italian-American botanist, physician, and naturalist Giovanni Antonio Scopoli made the first scientific description of this genus during the 1700s.

The northern catalpa is the species with the largest flowers. The tree can live up to 70 years and enjoys sunlight or partial shade. It has a rapid growth rate, which decreases with age, but can grow to be 10 feet within two years. The mature height of the northern catalpa ranges from 40 to 70 feet, while the mature spread is between 20 and 40 feet. The trees begin to flower after seven years, but it takes until age 10 before it begins producing quality seed crops.

The northern catalpa's seedpods remain attached to the tree all winter, until the flower clusters bloom in May and June. The flower's upright stalks range from 4 to 8 inches in length. Flower buds are small, rounded, and pale brown, and the nectar entices hummingbirds, tiger swallowtail butterfly larva, and bees. The white, tubular, and frilly-edged flowers have lower petals with yellow and purple spots. Each flower sports a unique line of spots about 2 inches in diameter.

Medium-sized, bell-shaped leaves are the backdrop for these flowers. The odorless leaves have a fuzzy texture, are without lobes, and turn a brilliant yellow in autumn. A unique feature of the tree is the opposite leaf arrangement, in which three leaves are whorled toward the stem tip. Leaves range from 6 to 12 inches in length and are almost 5 inches wide. Leaf scars, which resemble suction cups, are found on the winter twigs when the leaves fall.

The leaves are said to relieve pain when applied to wounds and abrasions. Tea made from the bark has been used as a antiseptic, an antidote to snakebites, a laxative, and a sedative. Because of its sedative nature and narcotic abilities, leaves were mixed with other herbs for the treatment of whooping and spasmodic coughs in children. The bark was used as a treatment for malaria, as a substitute for quinine.

The northern catalpa is soil- and drought-tolerant and transplants easily; however, it prefers deep, moist, fertile, and well-drained soil. A short and crooked trunk supports its broad range of slender branches and thick twigs. The reddish-brown to gray bark, when mature, ranges from scaly to rigid, some having square plates.

After the flowers fall off, 15-20 percent of the flower areas develop seedpods, also called beans or fruit. The narrow, cylindrical, dark brown pods mature in autumn, dangling from the tree limbs. They open in spring, splitting and spilling flat-fringed seeds to the ground, then falling themselves. As the 8- to 18-inch-long pods grow, they turn green and darken; once they reach full maturity, they eventually turn dark purple. Those mature pods can reach 1.5 feet in length.

Flowers and leaves distinguish the northern species from two others. Often used in landscapes, the Chinese catalpa (Catalpa ovata) has also been cultivated in Wisconsin. Its pale yellow flowers are smaller than those of other catalpas. The shape of its leaves distinguish it from the northern species; Chinese catalpa leaves have two pointed "fingers" sticking out from their centers, while northern species' leaves are more rounded.

The leaves of the heat-resistant southern catalpa (Catalpa bignonioides), commonly found in Alabama, have what some consider an unpleasant odor. The tree blooms later and has slightly smaller flowers than its northern counterpart.

In South Carolina, the Catawba (meaning "river people") tribe smoked the pods for medicinal and hallucinogenic purposes. They named the northern catalpa and gave it nicknames such as "Johnny Smoker," "Lincoln Log Tree," and "Indian Cigar Tree." The pods were collected and smoked after they had dried and turned brown. The trees were considered a symbol of honor, which gave them great importance in tribal society.

Despite its beauty, the tree's great size can be a liability to other plants, so take care if you're planting one in your yard. The expansive northern catalpa can crowd out or overly shade other trees or shrubs. Its main predator is the catalpa sphinx moth, a pest that can lay its eggs on the trees' leaves. These hatch into white and pale yellow caterpillars with black heads, black markings, and a black horn. They are particularly prized as catfish bait. The catalpa's leaves will grow back after being eaten by the caterpillars, but take care. If allowed to continue for several years, the incessant defoliation can kill a tree. Control breakouts of sphinx moth caterpillars with spray.