Pop quiz: What’s the best way to help butterflies in your backyard? If you answered “Plant butterfly bush,” you’re in good company. A recent survey of my gardening friends elicited the same response from more than a few. It’s easy to understand why: Aside from its self-reinforcing moniker, the plant...

They were like moths to a flame or, more accurately, butterflies to a native plant. No sooner had I unloaded two joe-pye weed perennials from my car last August than three tiger swallowtails dive-bombed the pots, as if to validate my purchase. If only my fellow shoppers knew what they were missing...