A cascara tree (Frangula purshiana or Rhamnus purshiana) is a small native North American tree, known for its attractive yellow fall foliage, small greenish flowers, and purple-black berries that feed birds; its bark contains a powerful natural laxative, historically used by Native Americans and in modern medicine, but it requires careful handling due to its strength and bitter taste. It's a versatile understory tree in the Pacific Northwest, thriving in various conditions from moist to dry.