As the name suggests, the shrub has spherical white flowers which the early botanists associated with handmade buttons used to decorate rich garments. To present-day visitors they rather bring to mind needle cushions (because of the protruding pin-like stamina). These associations are quite irrelevant to butterflies, which are especially fond of this species.
This North American shrub frequently grows in wetlands, and so it feel at home on the shore of a pond in the lower park. Its compact spherical shape makes it stand out from a distance, and it only gains in our eyes as we approach it.