Southern Catalpa (Catalpa bignonioides): Essential Guide Southern Catalpa (Catalpa bignonioides): Essential Guide Catalpa Tree Branches Pods Leaves Stock Photo 2586961485 Shutterstock Smoke Catalpa Pods Catalpa (Catalpa speciosa) The Northern Catalpa Tree Extension While catalpa trees are not generally considered highly toxic, some parts of the tree, particularly the roots, are known to be poisonous according to the USDA Plants Database. The leaves and seed pods Learn About Northern Catalpa Arbor Day Foundation