Clethra arborea flowers
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Ericales
Family: Clethraceae
Genus: Clethra

Between 30-70; see text.

Clethra is a genus of between 30-70 species of flowering shrubs or small trees. It is one of two genera in the family Clethraceae (the other being Purdiaea). The species may be evergreen or deciduous, and all bear flowers in clusters or inflorescences.

They are distributed from temperate to tropical climates in eastern and southeastern Asia, Malesia, Central America, northern South America, the southeastern United States, and one species (C. arborea) on the island of Madeira.

Selected species

The number of species accepted varies between different authorities depending on taxonomic interpretation, but with a recent trend to reduce the number recognised as distinct; the recent Flora of China has cut the number accepted for China from 35 to 7 species, and the USDA only recognises two in the United States, synonymising C. tomentosa with C. alnifolia. The following is a selection:

  • Clethra acuminata Michx. – Mountain Pepper Bush; southeastern United States.
  • Clethra alnifolia L. – Sweet Pepper Bush; eastern United States.
  • Clethra arborea Ait. – Lily of the Valley Tree; Madeira (considered extinct in the Canary islands, also present in the Azores).
  • Clethra barbinervis Siebold & Zucc. – Japanese Sweet Shrub; eastern China, Korea, Japan.
  • Clethra bodinieri – southern China.
  • Clethra brasiliensis – northeastern South America.
  • Clethra crispa – northwestern South America.
  • Clethra delavayi – southern China to Bhutan and Vietnam.
  • Clethra fabri – southern China, Vietnam.
  • Clethra fargesii – central China.
  • Clethra fimbriata – northwestern South America.
  • Clethra kaipoensis – southeastern China.
  • Clethra lanata – southern Mexico to Panama.
  • Clethra mexicana – southern Mexico, Central America.
  • Clethra obovata – northwestern South America.
  • Clethra ovalifolia – northwestern South America.
  • Clethra paralelinervia – northwestern South America.
  • Clethra petelotii – Vietnam, Yunnan.
  • Clethra pringlei - Mexican Summersweet; northeastern Mexico.
  • Clethra revoluta – northwestern South America.
  • Clethra rugosa – northwestern South America.
  • Clethra scabra – northeastern South America .