Sometimes known as the cigar tree for the long pods that turn brown in fall and are about the diameter of a cigar, catalpa trees (Catalpa spp.) have showy white flowers in spring and early summer. There are two native species, northern catalpa (Catalpa speciosa) and southern catalpa (Catalpa bignonioides). Both are planted as ornamental and shade trees, extending their distribution well beyond their original ranges. Trees are readily grown from seed.
Originally native to areas of the Mississippi River Valley drainage in the American Midwest, northern catalpa can reach 65 feet tall and is hardy in U.S. Department of Agriculture plant hardiness zones 4 through 8. Large heart-shaped leaves of the spreading canopy provide summer shade and yellow color before they drop in the fall. Large clusters of white 1/2-inch-wide flowers show well against the leaves. Flowers have ruffled petal edges and purple and yellow markings toward the middle of the petals. Fruit set is normally good, with many long slender green pods resembling green beans following the flowers.
Also called common catalpa, southern catalpa is a shorter tree about 50 feet tall and hardy in USDA zones 5 through 9. Native to the Gulf Coast states, it now grows in areas east of the Rocky Mountains, the Southwest and Oregon. Flowers are similar to northern catalpa but are more spotted with color and bloom two to three weeks later than northern catalpa. The leaves have a distinct smell when crushed, while northern catalpa leaves are scentless. Pods are similar to those of northern catalpa.
Seedpods and Seeds
Seedpods of both species mature as the summer progresses. Pods start out green and about 6 inches long, and grow to 24 inches long with a width of 1/2-inch by summer's end. The pods turn brown in the fall and are held on the trees during the winter, usually splitting open down the length of the pod in early spring. The winged seeds are released through the slit to disperse on the wind. Northern catalpa has blunter seed ends and southern catalpa seeds are more pointed at the end. Seeds are about 1 inch long and 1/3-inch wide. The winged edges that surround the seed have a fringe of hairs at the end.
Harvest the seedpods after they have turned brown, either in the fall or in late winter, before they split open to release the seeds. Fall-harvested seeds that are stored indoors have a lower germination rate than those left on the tree over the winter. Peel the seedpod apart to remove the seeds. Plant them in the spring or store seeds in the refrigerator in tightly sealed containers for one or two years. Seeds don't have a dormancy period and sprout about three weeks after sowing. Seeds can use light to germinate, so cover seeds lightly with soil when you sow them.