This month’s tree spotlight is northern catalpa (Catalpa speciosa), a tree native to the eastern half of the United states. It grows well in moist, deep, and well-drained soils. It can grow 40-70 feet in height and its crown spread is generally half of the height of the tree.
Northern catalpa has a medium tolerance to salt and grows well in conditions difficult for other trees, such as in poorly drained soils and in areas with high levels of air pollution. Northern catalpa wood was used by European settlers as fence posts, because the wood is lightweight and resistant to deterioration for several years. Railroad companies used the wood for train track ties and fuel wood. The tree is not desired by landscapers because of its high level of litter from the large leaves and seed pods. In addition to litter it is pre-invasive in Vermont and should only be planted in landscaped areas and needs to be monitored. It has been reported that some people can develop dermatitis after handling the flowers.
The northern catalpa is utilized by some wildlife such as the catalpa sphinx caterpillar which feed on the leaves and nectar released by the flowers, they can cause defoliation. The catalpa sphinx is a desired species for fishing bait. Broken off branches and trunks of older trees develop cavities and are used as dens by squirrels, other small mammals, and cavity-nesting birds.
The Big Tree Program is a national initiative that tracks and records the biggest trees of each species across the country. The Vermont Big Tree Program is based on the national program with a scoring system composed of 3 measurements: height, crown width, and circumference at breast height. The current champion northern catalpa is in Benson, Vermont. When it was last measured in 2002, its height was 82 feet, its average crown spread was 43 feet, and its circumference at breast height was 18 feet, with a diameter of 5 feet 8 inches.
Common names: northern catalpa, hardy catalpa, cigar tree
Height: 40 – 70 feet
Hardiness Zone: 4 – 8
Leaf: Leaves are whorled in groups of three (or opposite on the twigs), heart shaped, 5 to 12 inches long, pinnately veined (meaning they possess a prominent midrib running from base to apex with smaller veins running from the midrib), light green above with soft pubescence (or hairs) on the underside
Flowers: Monoecious (male and female flowers on a single tree), very showy, orchid like, bell shaped, white with yellow and purple spots, 1 inch long appear in open, branched, upright, terminal cluster (8 to 12 inches long), appear in late spring
Fruit: Long bean like 10 to 18 inches long, very stiff, and round in cross section, contains numerous flattened seeds with 2 papery wings; seeds mature in autumn, but capsule may remain attached over winter
Twig: Stout, green when young turning reddish brown in color, terminal bud is absent, lateral buds are small and covered with red-brown scales; leaf scars are unique elliptical or round, sunken, and light in color
Bark: Grey-brown, shallow fissures and scaly ridges when mature
Twig - 5488145- Rob Routledge, Sault College, Bugwood.org
Leaves - 0008308- Paul Wray, Iowa State University, Bugwood.org