Northern Catalpa

Size, growth and what to expect

By the USDA Plant Guide's figure, a northern catalpa stands about 20 feet at 20 years, rapid in youth and slowing with age. Our growth estimator models that youthful pace at nearly three feet a year on an average site, its rate for a fast tree. It reaches 40 to 70 feet with an irregular, open crown and lives about 60 years. It can live up to 100 years.

It flowers in late spring in upright clusters 4 to 8 inches tall of white bells striped orange and spotted purple, good for honey. The pods that follow run 10 to 24 inches long, turn dark brown in fall and split in spring to drop winged seeds. Their shape and color give the tree its other name, cigar tree. The caterpillars of the catalpa sphinx moth strip it some years and are prized as fish bait.

Its native ground is a small area of the central Mississippi Valley in western Tennessee, northeast Arkansas, eastern Missouri, western Kentucky and southern Illinois and Indiana. After 200 years of planting it grows across most eastern states.

How to grow Northern Catalpa

Catalpa wants room and sun. It grows in full sun or part shade, on dry, average or wet soil. Its crown grows wide, so keep it 30 feet from the house, away from a patio, and never under a power line. Set trees 20 feet apart.

Plant while dormant. Saplings arrive bare-root or potted. Dig two to three times the root width but no deeper, keep the root flare visible at grade, refill with what you dug, and mulch a ring clear of the trunk. Stake only if the top whips in wind. For seed, split the pods in late winter and sow the flat winged seeds a quarter inch deep in spring, under screen.

Give it a soaking each week through its first summer. Guard the trunk from rabbits and voles, and cage against deer two or three winters. Prune in winter while the tree is young, keeping one leader and cutting out tight forks.

Each flower carries both male and female parts. Northern catalpa sets pods only with pollen from another tree, so plant two or more seedlings for seed. Bumblebees and carpenter bees work them by day and moths by night. The wood is brittle and big limbs break in storms, reason enough to keep northern catalpa away from anything you value. Catalpa sphinx caterpillars strip a tree some summers, though it leafs out again. Leaves come late in spring and drop at the first hard frost.