pan-tropical, mostly South America
Alternanthera hassleriana Chodat [also known as A. aquatica Chodat] (D. Parodi)
A. ficoidea (L.) Sm.
A. reineckii Briq. (and varieties)
A. sessilis (L.) DC. (and varieties)
U.S. Federal Noxious Weed: Alternanthera sessilis
Alternanthera philoxeroides (Mart.) Griseb. and A. sessilis have become established in most tropical, subtropical, and even some temperate regions of the world.
Perennial. Decumbent, with erect and creeping stems; adventitious roots produced from individual nodes along stem as it lengthens; creeping (floating) stems may swell with aerenchyma for buoyancy. Leaves opposite, decussate, sessile, lanceolate, ovate or obovate. Inflorescence axillary or terminal, of sessile or stalked, typically white, pink or purple heads. Perianth segments 5. Reproduces by seeds or stem fragments.
inhabits rivers, lakes, swamps; occasionally terrestrial
Alternanthera comprises approximately 80-100 species, mostly from South America. The identity of species presently traded in the aquarium and pond plant industries is vague, with numerous varieties being produced and sold under commercial and existing taxonomic names (e.g., 'Lilacina' and ‘Rosaefolia’).