Buttonbush flowers are perfect spheres, an inch across, white and bristling with protruding styles like a pincushion or a small firework caught mid-burst. The whole shrub goes over in midsummer, and for the two or three weeks the flowers last they are covered in bees, wasps, and swallowtails from morning until the light goes.

Cephalanthus occidentalis is a native of pond margins, ditches, and swamp edges across most of North America, and takes standing water for months at a stretch, which makes the shrub one of the few genuinely reliable answers for the wettest corner of a property. Waterfowl eat the seed heads through winter. Give the plants sun and wet feet, cut hard every few years to keep the frame from going leggy, and otherwise let them be.