The passage of midsummer leaves an indelible signature in the botanical world, and one of the easiest places to read the writing is on the mid-August blooms of a plant known as Joe Pye Weed. There are several species of Eutrochium in our area—the genus name used to be Eupatorium, but the DNA police swooped in to require a change—and they all start flowering at the height of the Dog Days, when the heat and humidity are at their zenith and you just can't believe that any plant would have the energy to blossom. Certainly, this naturalist doesn't. But Joe Pye Weed does, and in its flowers maybe, just maybe, you can discern the beginning of the end of what I've long seen as oppressive weather. In any event, the floral display is a magnet for butterflies, and on a recent foray—it doesn't really matter where; Joe Pye Weed can be found happily growing in just about any overgrown field you look—I spotted Monarchs, Viceroys, Spicebush Swallowtails, Sulphurs, Cabbage Whites, various Skippers, and this beauty, a Tiger Swallowtail. Joe Pye, the plant's namesake who, recent scholarship suggests, was a real person in colonial New England, would have been proud.