Clethraceae is a small family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

s in the order Ericales

Ericales

The Ericales are a large and diverse order of dicotyledons, including for example tea, persimmon, blueberry, Brazil nut, and azalea. The order includes trees and bushes, lianas and herbaceous plants. Together with ordinary autophytic plants, the Ericales include chlorophyll-deficient...

, native to warm temperate to tropical regions of Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 and the Americas

Americas

The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, with one species also on Madeira

Madeira

Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...

. The family comprises two genera, Clethra

Clethra

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...

and 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...

.

In the past, most botanists included only Clethra in the family, but recent research has shown that the genus Purdiaea, previously placed in the closely related family Cyrillaceae

Cyrillaceae

Cyrillaceae is a small family of flowering plants in the order Ericales, native to warm temperate to tropical regions of the Americas. The family comprises two genera, each with a single species, Cyrilla racemiflora and Cliftonia monophylla....

, is more closely allied to Clethra (Anderberg & Zhang 2002).