Alternanthera

These are annual or perennial herbs or subshrubs. While some of the better-known species are aquatic plants, most are terrestrial. ==Species==

'' '' It is not yet clear how many species belong in the genus. Estimates range between 80 and 200. Plants of the World Online accepts 106 species. sea-urchin joyweed • Alternanthera fasciculata • Alternanthera fastigiata • Alternanthera ficoidea – parrot leaf • Alternanthera filifolia (Hook.f.) J.T.Howell • Alternanthera flava • Alternanthera flavescens – yellow joyweed • Alternanthera flavicoma • Alternanthera flavida • Alternanthera flosculosa • Alternanthera galapagensis • Alternanthera geniculata • Alternanthera glaziovii • Alternanthera grandis • Alternanthera halimifolia – West Indian joyweed • Alternanthera helleri (B.L.Rob.) J.T.Howell • Alternanthera herniarioides • Alternanthera hirtula • Alternanthera inaccessa • Alternanthera indica • Alternanthera ingramiana • Alternanthera jacquinii • Alternanthera januarensis • Alternanthera kanhae • Alternanthera kurtzii • Alternanthera laguroides • Alternanthera lanceolata • Alternanthera laxa • Alternanthera littoralis P.Beauv. – seaside joyweed • Alternanthera lupulina • Alternanthera macbridei • Alternanthera martii • Alternanthera micrantha • Alternanthera microphylla • Alternanthera minutiflora • Alternanthera mollendoana • Alternanthera multicaulis • Alternanthera nahui • Alternanthera nesiotes • Alternanthera nodiflora – common joyweed • Alternanthera obovata • Alternanthera olivacea • Alternanthera panamensis • Alternanthera paronichyoides A.St.-Hil. – smooth joyweed • Alternanthera pennelliana • Alternanthera peruviana • Alternanthera philippo-coburgii • Alternanthera philoxeroides (Mart.) Griseb. – alligator weed • Alternanthera porrigens • Alternanthera praelonga • Alternanthera puberula • Alternanthera pubiflora • Alternanthera pulchella • Alternanthera pulverulenta • Alternanthera pumila • Alternanthera pungens • Alternanthera pycnantha • Alternanthera raimondii • Alternanthera regelii • Alternanthera reineckii Briq. • Alternanthera robinsonii • Alternanthera rufa • Alternanthera rugulosa • Alternanthera serpens • Alternanthera serpyllifolia • Alternanthera sessilis (L.) DC. – rabbit-meat, sessile joyweed, downy joyweed, hairy joyweed • Alternanthera snodgrassii • Alternanthera spinosa • Alternanthera stellata • Alternanthera stenophylla • Alternanthera suessenguthii • Alternanthera tetramera • Alternanthera tomentosa • Alternanthera tubulosa • Alternanthera vestita • Alternanthera villosa Formerly placed here • Gomphrena subscaposa (as Alternanthera subscaposa ) ==Ecology==

Many species have been reported as noxious weeds, including A. angustifolia, A. caracasana, A. denticulata, A. nana, A. nodiflora, A. paronychioides, A. philoxeroides, A. sessilis, A. tenella, and A. triandra. The most important species is alligator weed (A. philoxeroides), a South American aquatic plant that has spread to other continents. It is a weed of many kinds of agricultural crops, it is an invasive species that degrades native habitat, and its dense mats of vegetation clog waterways, slowing shipping and increasing flooding. Alternanthera plants are known to produce allelopathic compounds that injure other plants, including crops. Biological pest control agents now in use to reduce alligator weed infestations include the alligator weed flea beetle (Agasicles hygrophila), the alligator weed thrips (Amynothrips andersoni), and the alligator weed stem borer (Arcola malloi). ==Uses==

A. philoxeroides and A. sessilis are eaten as vegetables in parts of Asia. Some Alternanthera are used as ornamental plants. ==References==