There's also the matter of leaf type. If the plant is a vine, or the leaves grow in strings, it quite likely has effects on the circulation of blood. And those that grow best by water or in very wet climates are quite likely good at spurring urination.
另外就看葉形，若是有藤或成串的，跟血液循環的功能可能有關連，而長在水草邊、濕氣重的，很可能就有利尿作用。