Western (Northern) Catalpa- Catalpa speciosa
It is surprising that a tree that looks so different from the other Colorado-adapted trees, is so successful. What stands out immediately are the huge leaves which can be 3”x 6” or even 6” x “12” and are heart-shaped. And in June, this large shade tree blooms exquisite, ruffled, bell-like, white, fragrant flowers with yellow and purplish coloration .And in the fall the passerby might be surprised to see the long thin pods 10”- 18” long.
This exotic-looking tree comes home from the nursery looking like a stick, generally lacking a well-developed crown, but grows rather quickly, eventually reaching 40’-60’ tall and 20’- 40’ wide. Unless the central leader is damaged or pruned back, the Western Catalpa generally grows upright which makes it useful in narrower spaces. Compacting the top will make it spread wider. Even though the wood is fairly brittle, it seems to suffer little storm damage, mostly to small branches. The branches usually have strong crotches (unions to the trunk or primary branches) and its habit of leafing out very late contribute to its structural success in Colorado.
Catalpa speciosa is very adaptable as to soils and water conditions, thriving in moist, rich soils but also doing fine in dry, lean, alkaline soils. However a deep soaking once a month in dry periods will help them to grow faster and be stronger. It is generally accepted as a xeriscape tree.
Some people do not like cleaning up the spent flowers, the big leaves and the beans; some say the architecture is coarse. But every tree like every person has its pluses and its minuses. Altogether the Western Catalpa is a highly successful tree for Colorado up to 6000’ as can be seen in many older neighborhoods. New residents to the bare plains surrounding our cities could profit from the fast-growing presence of this hardy, heat-tolerant, adaptable and beautiful tree.