Although it is a native tree, Catalpa is difficult to include in residential landscapes because of its coarseness of shape and brittle branches and seed pods that drop, as well as the fall litter of unattractive yellow and brown leaves.
But its 8 to 10-inch upright panicles of tubular white flowers that appear in late May and June are glorious; dots of yellow and stripes of purple spread across each frilly lobe. By day the flowers are pollinated by bumblebees, and by night, moths. Seeds form in 8 to 20-inch long pods that will persist throughout the winter.
The tree’s irregular shape and crooked branches can look very bold and rugged in the winter landscape. This habit, as well as the flowers, dangling seed pods and the large heart-shaped leaves make the catalpa an easy tree to identify in the landscape.
The difference in the northern catalpa, Catalpa speciosa, and the southern catalpa, Catalpa bignonioides, is mostly in the height of the tree, number of flowers on each panicle and size of the seed pod as well as its regional distribution.
Martha Van Artsdalen
Originally posted at: http://www.haverford.edu/news/stories/60901/16