The Catalpa Tree and Its Caterpillars

There are two catalpa (also called "catawba") species in North America and they are both natives. Catalpa can be recognized by its large heart-shaped, sharp-pointed leaves, showy white or yellow flowers and long fruits which resemble a slender bean pod.

A Naturalized Catalpa Tree

catalpa trees on lake dam
Catalpa on Lake Dam. (Steve Nix Photo)

Catalpa speciosa (Northern Catalpa) grows into a loose oval leaf shape, 50 feet tall in most urban locations, but occasionally grows to 90 feet under optimum conditions. This large-leaved tree spreads 50 feet and tolerates hot, dry weather, but leaves may scorch and some drop from the tree in very dry summers. The leaves of speciosa are opposite.

Catalpa bignonioides (Southern Catalpa) is somewhat smaller, reaching only about 30 to 40 feet tall, leaves are arranged opposite or in whorls and a southern U.S. native. A sunny exposure and a well-drained, moist, rich soil is preferred for best growth of Catalpa but the tree will tolerate a range of soils from acid to calcareous. It is sometimes called the Indian bean tree.

Both trees have a coarse, very open growth habit forming an irregularly shaped crown. Catalpa has a moderately long life (60 years or so), but trunks on large trees often contain rot. Catalpas are very adaptable and they are tough trees, having naturalized in many parts of the south.

The Adaptable Catalpa Tree

Catalpa Leaf and Fruit
Catalpa Leaf and Fruit. (Steve Nix Photo)

Catalpas are very adaptable and tough trees, having well adapted or naturalized in many parts of the southern United States. Catalpa is often used as a land reclamation plant because it successfully grows where air pollution, poor drainage, compacted soil, and/or drought can become a problem for other species. It produces lots of shade and is a fast grower.

The largest living catalpa tree is on the lawn of the Michigan State Capitol, which was planted at the time the Capitol was dedicated in 1873. The oldest known living catalpa tree is actually in the United Kingdom, a 150-year-old specimen in the Minster graveyard of St. Mary's Butts in the town of Reading, Berkshire.

Young catalpa trees are beautiful green standouts with giant green leaves that can sometimes be confused with tung trees and royal paulownia in the southern U.S. Catalpa seedlings are somewhat available, but you may have to go out of your region to find the tree. Catawba's USDA hardiness zones are 5 through 9A and ​it grows from coast to coast.

Catalpa Characteristics

Catalpa Tree
Catalpa Tree. (Steve Nix Photo)

Catalpa growth is rapid at first but slows down with age as the crown begins to round out and the tree increases in spread. The main ornamental feature is flower panicles of white with yellow and purple markings produced in spring and early summer, depending on the particular tree.

Leaves fall throughout the summer in USDA hardiness zone 8, making a mess and the tree looks ragged with yellow leaves in late summer. Flowers make somewhat of a slimy mess for a short period when they drop on a sidewalk but are no problem falling into shrubs, groundcovers, or turf. Spent bean pods also make a mess and can look a bit course alongside the green pods.

Catalpa bark is thin and easily damaged from mechanical impact. The limbs will droop as the tree grows, and will require pruning for vehicular or pedestrian clearance beneath the canopy. Pruning is required to develop a strong structure. The limbs are resistant to breaking and very stout.

The Catalpa Fruit

Catalpa With Fruit
Catalpa With Fruit. (Steve Nix Photo)

The Catalpa fruit is a long seed pod growing up to two feet long. The fruit resembles a large string bean and can be a slight litter problem after seeds are dispersed. The old pod shells are persistent on limbs but will eventually drop. Still, the pod is quite interesting and adds flavor to an ornamental specimen.

The tree is useful in areas where quick growth is desired, but there are better, more durable trees available for street and parking lot plantings. Sixty-year-old trees in Williamsburg, Virginia have three to four-foot-diameter trunks and are 40 feet tall. Catalpa can be invasive and often escapes cultivation and invades surrounding woodlands.

A Catalpa Worm Infestation

Catalpa Worm Damaged Tree
Catalpa Worm Damaged Tree. (Steve Nix Photo)

This catalpa tree is under attack by the larva of the catalpa sphinx moth. All of the photo specimens you see here came off that one tree.

This sphinx moth larva is one of just a few insects that infest catalpa and can eat large quantities of leaves. The caterpillar is yellow with black lines and markings. The tree is regularly defoliated and often looks terrible by the end of the summer.

Catalpas are often planted to attract these catalpa "worms," a large caterpillar prized for fish bait because the skin is very tough and the caterpillar is juicy. The caterpillar can be frozen for use as a fish bait at a later time. The caterpillar can defoliate the tree once or twice a year but appears to be no adverse consequences to the health of the tree.

The Catalpa Sphinx Moth

mature catulpa worm
Mature catulpa worm. (Steve Nix Photo)

The larval stage of Ceratomia catalpae is known as the catalpa or catawba worm. When first hatched, these larvae are a very pale color, but become darker toward the last instars. The yellowing caterpillars will usually have a dark, black stripe down their back along with black dots along their sides.

They grow to a length of about two inches and feed on the leaves of the Northern catalpa and, more commonly, the Southern catalpa. The fully developed caterpillar has a conspicuous black spine or horn on the back at the insect's rear. Catalpa sphinx moth caterpillar is usually plump with forage and are beautiful when mostly yellow with black lines and spots in the last color phase. They are highly desired by fisherman as bait.

Fishing with Catalpa Worms

Bucket of Catalpa Worms
Bucket of Catalpa Worms. (Steve Nix Photo)

The catalpa caterpillar is tough in texture. The worm oozes a bright fluorescent green fluid that smells sweet when put on a hook. The tough skin makes for staying hooked and a fresh worm will attract fish with its smell and its wiggle. It is revered as the best fish bait to be found naturally.

Catalpa worms can be preserved alive by placing them in cornmeal packed in an airtight container and frozen. It has been said that when this container is opened and the worms are removed from the meal, they thaw and become active and as effective in catching fish as ever.

Another method of preserving the caterpillar for future use is "pickling" them in a baby food jar filled with corn syrup. The jar should be immediately stored in a refrigerator and has an indefinite shelf life.