Most of the tree species in North America that feature seed pods belong to the Legume family, but certain other types possess seed pods as well. These seed pods help add to the landscaping appeal of these trees, hanging down and sometimes remaining on the tree well into the colder months after all the leaves are gone. Different types of seed pods occur on these trees, defined by their sizes or appearance.
Long Seed Pods
Native to the Midwest but introduced as a landscaping tree to other portions of North America, northern catalpa (Catalpa speciosa) has very long seed pods. Reaching lengths from 8 to 20 inches, the pods mature from colorful flowers that bloom during June. Catalpa pods turn brown over time and stay on the tree until falling off the following spring. Chilopsis linearis, the desert willow, is a Southwestern cousin of catalpa, featuring pods as long as 9 inches. The pods stay on through winter. Leaves of the desert willow are long and narrow, similar to those of actual willow trees.
Short Seed Pods
Showy flowers that bloom from the branches are a highlight of the eastern redbud (Cercis canadensis) but the seed pods they yield are also noteworthy. Although few exceed 3 inches in length, they are numerous, flat and brown. Redbuds are small enough at between 20 to 30 feet for nearly any landscaping scenario. Yellowwood (Cladrastis kentuckea) produces 2 ½-to 4-inch pods. The tree, a native of states such as Arkansas and Kentucky, grows to 60 feet, but its biggest branches are just 6 feet high, allowing you to see the pods easily.
Flattened Seed Pods
The seed pods on a black locust (Robinia pseudoacacia) are smooth, purple-brown and flat. Growing on average between 30 and 50 feet, black locust has spines on its branches, but also has handsome compound leaves and drooping clusters of flowers in springtime. Black locust is a good option for places where other trees falter. Blue palo verde (Cercidium floridum) is another tree of the dry Southwest, growing to 30 feet. Its flattened seed pods turn white over time, but start out shades of brown. This species works well by itself or when planted in groves.
Curly, Twisting Seed Pods
The catclaw acacia (Acacia greggii) grows to 25 with multiple stems. It has a thorny, twisting trunk, with its fragrant, yellow flowers generating twisting, curly seedpods up to 3 inches long. The pods begin to curl as they dry out, adding to this tree's interest as a species suitable for residential areas in the Southwest. Another tree of the American Southwest, screwbean mesquite (Prosopis pubescens) features "corkscrew-curled" pods, notes the University of Arizona Pima County Cooperative Extension. Thorns also cover its trunk and limbs, as screwbean mesquite develops between 25 and 40 feet. The pods give screwbean mesquite ornamental worth during summer.