Although native to wetlands throughout much of eastern North America, common buttonbush (Cephalanthus occidentalis, Rubiaceae) is particularly common in the Florida Everglades. I came across several of these woody shrubs along the Anhinga Trail at Everglades National Park last spring.
Buttonbush is adapted to full sunlight and wet soil and thrives even while standing in several feet of water. Shade and drier conditions adversely affect growth, survival, and flower development. Although the large, round clusters of flowers are beautiful, these plants are also toxic. The bark produces a compound known as cephalathin which can cause vomiting, convulsions, and paralysis if ingested.