English: Riceweed.
Genus: 1 species.
Region: widespread, Africa, Asia, Australia.
Habitat: tropical; sandy sites liable to inundation and desiccation; plains, banks and edges of rivers and lagoons; on sandy or muddy soils that can be seasonally flooded; elevations from 90 to 750 metres; prefers a sunny position; toleratea extreme heat, periodic inundation, drought.
Culture: considered a weed, growing in rice fields.
Use: medicinal.
BotanyHerb; prostrate, spreading; annual; forms large mats; 20 cm tall.
Root: woody rootstock; taproot, white or brown.
Stem: procumbent; flat, solid, hairy; much-branched; up to 40 cm long.
Leaves: simple; lobed or divided; alternate, spiral, sessile or stalked; elliptic to ovate; hairy and or scabrous on both sides; apex obtuse or rounded; bases asymmetrical; pinnately veined; stipules absent.
Flowers: bisexual, single, axillary, petals 4, white.
Fruit: nut-like.
Seed: partly thick and corky coat.
Dispersion: by water.
TaxonomyColdenia was traditionally included in
Boraginaceae, subfamily Ehretioideae. Molecular data revealed it to be more closely related to the genus Cordia, so that other authors placed in Cordioideae. Subsequently, it was placed in its own family, Coldeniaceae, within the
Boraginales order, by the
Boraginales Working Group.