(Cephalanthus), genus of shrubs or small trees of the madder family (Rubiaceae, q.v.) native to Africa, Asia, and North America. It was named for its fragrant, creamy white, spherical flowers, about 2.5 centimetres (1 inch) in diameter. There are at least 6 species of buttonbush. Cephalanthus occidentalis, the most common, grows about 6 meters (20 feet) high.
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