A handsome, spreading deciduous tree native to a large area of the American Midwest, the northern (or western) catalpa (Catalpa speciosa) grows 40 to 60 feet tall and 25 to 45 feet wide. In early summer, it produces attractive clusters of small white flowers marked with yellow and purple spots. By later summer and into fall, the long seed pods are easily seen, some measuring as long as 20 inches. Grow northern catalpa in USDA hardiness zones 4 through 8, where winter low temperatures range from -30 to 20 degrees Fahrenheit.
The bright kelly-green leaves of the northern catalpa are heart-shaped or arrowhead-like. The tip of the leaf has a very thin point that resembles a "drip tip" usually found on leaves of many tropical rainforest trees.
When mature, the northern catalpa leaf blade measures between 6 to 12 inches long and about one-half that in width. Regardless of size, the leaf is always longer than it is wide.
The leaf is entire, or "simple," meaning that it has no teeth on the edges. On large leaves, the edges seem to buckle or gently wave to make the leaf look like it may have hints of very shallow lobes. The green upper surface of the leaf blade is smooth while the underside is fuzzy in texture and more grayish-green. It feels very soft and flexible. The veins branch off the leaf's mid-rib in parallel rows (like a feather structure) and further divide and diminish into the leaf tissue.
Arrangement on Tree Branches
On the tips of branches where the new growth dominates, the leaf petioles (stems) attach in a whorling arrangement. According to Virginia Tech University, a whorled tip of leaves often has three leaves, with two much larger in size than the third. Further back on branches, the typical arrangement alternates much more.
In autumn, the leaves of the northern catalpa become significantly paler--a yellow-green. Depending on the weather and other growing season conditions, the leaves can attain a more yellowy tone before dropping off the tree.