Diodia (or buttonweed) is a genus of flowering plants in the family Rubiaceae. It was described by Carl Linnaeus in 1753. The genus is found from southern and eastern United States, South America, Central America, Mexico, the West Indies and tropical Africa.
Other buttonweeds
Many species of Diodia have been transferred to a closely related genus Diodella, and therefore the name buttonweed also applies to these species. There are also many species of false buttonweeds in the related genus Spermacoce. Abutilon theophrasti in the family Malvaceae is also known by the common name of buttonweed.
Species
Diodia aulacosperma K.Schum. - Socotra, Somalia, Kenya, Tanzania
Diodia barbata (Poir.) DC. - Guyana, Dominican Republic
Diodia barbigera Hook. & Arn. - Mexico
Diodia blepharophylla Standl. - Mexico
Diodia discolor DC. - French Guiana
Diodia flavescens Hiern - Angola, Zambia
Diodia indecora DC. - Mexico
Diodia kuntzei K.Schum. - Venezuela, Bolivia, Peru, Brazil, Argentina, Paraguay
Diodia lithospermoides K.Schum. - Peru
Diodia macrophylla K.Schum. - Brazil, Paraguay
Diodia microcarpa K.Schum. ex Glaziou - Brazil
Diodia mitens Bello - Puerto Rico
Diodia othonii Rizzini - Brazil
Diodia paludosa Kuntze - Paraguay
Diodia perforata Urb. - Haiti
Diodia rubricosa Hiern - Ghana, Ivory Coast, Liberia, Nigeria, Sierra Leone
Diodia saponariifolia (Cham. & Schltdl.) K.Schum. - Central and South America
Diodia saponarioides C.Presl - Mexico, Brazil, Argentina, Paraguay
Diodia scandens Benth. - Western, Central, and Eastern Africa
Diodia simplex Sw. - Cuba, Jamaica
Diodia verticillata Vahl - Brazil, Lesser Antilles
Diodia virginiana L. - Virginia buttonweed - south-central and south-eastern United States from Texas to Kansas, east to Florida and New Jersey; also Connecticut, Cuba and Nicaragua. Naturalized in Japan, Taiwan and northern California
