Smoke Catalpa Pods Catalpa (Catalpa speciosa) The Northern Catalpa Tree Extension Southern Catalpa (Catalpa bignonioides): Essential Guide Southern Catalpa (Catalpa bignonioides): Essential Guide 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 How Good Is Catalpa Firewood? Axe Adviser