John Hart Asher was feeling low one day in early November, until he stepped outside into a commotion of busy wings. Dozens of butterflies—mostly queens and monarchs but also sulphurs, eastern commas, and common buckeyes—were congregating in his yard in East Austin. Asher’s mood lifted as he watched the insects fluttering in the golden light above a cloud of small, lavender-colored blossoms.His Gregg’s mistflower (Conoclinium greggii) was performing just as he’d intended it to. In his work as an environmental designer, Asher (who also hosts PBS’s Central Texas Gardener show) often plants mistflowers next to walkways, where passersby can witness “explosions” of butterflies. “It’s a beautiful flower, but it’s one of these plants that, when it’s kickin’, it’s an experience,” he said.The Gregg’s mistflower puts…