Northern Catalpa

Catalpa Speciosa

by John Brouwer

The northern catalpa is a spectacular landscape tree with an abundance of showy white flowers in early July. Its flowers and large heart-shaped leaves give it a tropical appearance and therein lies a mysterious past and a continuing debate among botanists and arborists.

All the experts are agreed that since the ice age the native range of the northern catalpa has been confined to the central part of the Mississippi valley. And all are agreed that native and later European settlement patterns brought the tree into the current northern limits of its range. The debate rages as to whether it is a native or invasive tree and this hinges on where it was before the ice age.

And the heart of the debate is why a northern species limited itself to the confines of the central Mississippi valley when it has the genetic capacity to withstand the -30 Celius winters of southern Canada. Those who argue a wider native range base their argument on pre-ice age conditions where the tree must have thrived in northern climates to have evolved the capacity to withstand moderate Canadian winters. The ice-age forced all species south but for some unknown reason the northern catalpa never migrated back north until human intervention assisted its northern migration. The purists maintain that outside its Mississippi valley range, northern catalpa is an invasive species. The debate will continue until some fossil evidence is found locating northern catalpa in the north before the ice-age. A similarcontroversy developed around honey locust before fossil evidence found it was much more widely distributed before the ice age.

The northern catalpa is a separate species but related to the southern catalpa (catalpa bignioides).

Catalpas have 10-20 inch long narrow seed pods which stay attached through most of the winter and then split open to release winged seeds to the wind. Trees grow rapidly and begin to flower after seven years, They can reach a mature height of 60-70 feet and live for 70 years.

American fishermen are fond of the catalpa since it is host to the catalpa sphinx caterpillar, popular as fish bait.

Early settlers planted catalpa as it was a fast-growing tree which was ideal for fence posts as the heartwood is rot-resistant. (This could provide a contemporary alternative to the chemical laden pressure-treated lumber creating a toxic soup in millions of backyards.) Railway companies had plantations of catalpa to supply track ties and fuel. It has been used as telephone and power line poles.

Carpenters used catalpa for interior trim and furniture. Because it is fast-growing, catalpa is used in land reclamation projects and shelterbelts. Occasionally it is used as tonewood in musical instruments.

The leaves of catalpa relieve pain when applied to wounds and abrasions. Tea from the bark was used as an antiseptic, an antidote to snake bites, a laxative, and a sedative. Because of it sedative nature and narcotic effects, leaves were mixed with other herbs for the treatment of whooping cough. The bark was used in the treatment of malaria as a substitute for quinine.

Catalpa is now used mainly as a landscape tree for large yards. Locally it is found in Victoria park, on the University of Waterloo campus, as a street tree close to Wilfred Laurier, and occasionally in yards. Belmont Conservation Area has a spectacular stand between the entrance and the dam.

At Beaver Creek, a catalpa is growing between blocks 6 & 7. One was planted behind the entrance sign and along the fence behind the community center. The tree between blocks 6 & 7 should develop blossoms within the next two years. The others are younger and will take a few more years to develop their displays.

August 2010