Clethra

Clethra is a genus

Genus

In biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...

 of between 30-70 species

Species

In biology, a species is:* a taxonomic rank or* a unit at that rank ....

 of flowering shrub

Shrub

A shrub or bush is a horticultural rather than strictly botanical category of woody plant, distinguished from a tree by its multiple stems and lower height, usually less than 5-6 m tall. A large number of plants can be either shrubs or trees, depending on the growing conditions they experience...

s or small tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s. It is one of two genera in the family Clethraceae

Clethraceae

Clethraceae is a small family of flowering plants in the order Ericales, native to warm temperate to tropical regions of Asia and the Americas, with one species also on Madeira...

 (the other being Purdiaea

Purdiaea

Purdiaea is a genus of 11-19 species of flowering plants in the family Clethraceae. It is one of two genera in this family, and was formerly classified in the related family Cyrillaceae...

). The species may be evergreen

Evergreen

In botany, an evergreen plant is a plant having leaves all year round. This contrasts with deciduous plants, which completely lose their foliage for part of the year....

 or deciduous

Deciduous

Deciduous means falling off at maturity or tending to fall off and is typically used in reference to trees or shrubs that lose their leaves seasonally and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

, and all bear flowers in clusters or inflorescences.

They are distributed from temperate

Temperate

In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. But in continental areas, such as central North America the variations between summer...

 to tropical climates in eastern and southeastern Asia

Asia

Asia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...

, Malesia

Malesia

Malesia is a biogeographical region straddling the boundary of the Indomalaya and Australasia ecozones. Malesia was first identified as a floristic province that included the Malay Peninsula, Indonesia, the Philippines and New Guinea, based on a shared tropical flora derived mostly from Asia but...

, Central America

Central America

Managua
Guatemala City
San Salvador
San Pedro Sula
Panama City
San José, Costa Rica
Santa Ana, El Salvador
León
San Miguel|-|}...

, northern South America

South America

South America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...

, the southeastern United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and one species (C. arborea) on the island of Madeira

Madeira

Madeira is a Portuguese archipelago in the mid Atlantic Ocean that lies between and . It is one of the Autonomous regions of Portugal, with Madeira Island and Porto Santo Island being the only inhabited islands...

.

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
  Clethra alnifolia
  Clethra alnifolia , is a flowering plant in the genus Clethra, native to eastern North America from southern Nova Scotia and Maine south to northern Florida, and west to eastern Texas....
  
  L. – Sweet Pepper Bush; eastern United States.
• Clethra arborea Ait. – Lily of the Valley Tree; Madeira.
• 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 .