The Collaborative International Dictionary
Cephalanthus occidentalis
Buttonbush \But"ton*bush`\, n. (Bot.) A shrub ( Cephalanthus occidentalis) growing by the waterside; -- so called from its globular head of flowers. See Capitulum.
Wikipedia
Cephalanthus occidentalis
Cephalanthus occidentalis is a species of flowering plant in the coffee family, Rubiaceae, that is native to eastern and southern North America. Common names include buttonbush, common buttonbush, button-willow and honey-bells.