Learn About Northern Catalpa Arbor Day Foundation Northern Catalpa (Catalpa speciosa): A Complete Guide 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 No these aren't giant tree green beans, but instead the seed pod of the northern catalpa. These bean like pods can grow to be 20" long and contain numerous 1" long seeds. #haverfordcollegearboretum # Catalpa tree leaves and bark for pods? : r isopods