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Webster 1913 Edition

Noun.

(Bot.)

A shrub (

Cephalanthus occidentalis

) growing by the waterside; – so called from its globular head of flowers. See

a buttonbush (Cephalanthus occidentalis)

buttonbush ‎(plural buttonbushes)

Any of the genus Cephalanthus of flowering plants in the madder family.
1. (US) Cephalanthus occidentalis, the common buttonbush
  - 2008 March 6, Anne Raver, “To Feed the Birds, First Feed the Bugs”, in New York Times:
    The buttonbush shrub, which has little white flowers, feeds 18 species of butterflies and moths; and blueberry bushes, which support 288 species of moths and butterflies, thrive in big pots on a terrace.
Any of the genus Conocarpus of two species of tropical flowering plants; a mangrove.

any Cephalanthus

common buttonbush — see common buttonbush