Indian Bean Tree Gardening In Pearls Catalpa Yale Nature Walk 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 Southern Catalpa (Catalpa bignonioides): Essential Guide Northern Catalpa Came across this tree in Hudson, WI that looked like it had giant green beans growing off of it, looked it up and it's called a Northern Catalpa often known as a "