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[[File:Linedrawing Amaranthus spinosus.gif|thumb|1, part of flowering plant; 2, male flower with bracteoles; 3, fruit. Source: PROSEA]]
<big>''[[Amaranthus spinosus]]'' L.</big>
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{{DISPLAYTITLE:''Amaranthus spinosus'' (PROTA)}}
:Protologue: Sp. pl. 2: 991 (1753).
:Chromosome number: 2''n'' = 34
== Vernacular names ==
*Spiny amaranth, prickly amaranth, spiny pigweed (En). *Amarante épineuse, épinard malabar, épinard piquant (Fr). *Amaranto, bredo (Po). *Mchicha (Sw).
== Origin and geographic distribution ==
''Amaranthus spinosus'' has numerous medicinal uses. The root is known as an effective diuretic. In South-East Asia a decoction of the root is used to treat gonorrhoea and is also applied as an emmenagogue and antipyretic. In many countries, including those in Africa, the bruised leaves are considered a good emollient and applied externally in cases of eczema, burns, wounds, boils, earache and haemorroids. The plant ash in solution is used to wash sores. Plant sap is used as an eye wash to treat ophthalmia and convulsions in children. In Malaysia ''Amaranthus spinosus'' is used as an expectorant and to relieve breathing in acute bronchitis. In mainland South-East Asia, it is also used as a sudorific, febrifuge, antidote to snake poison, galactagogue, and to treat menorrhagia. Some tribes in India apply ''Amaranthus spinosus'' to induce abortion.
== Properties ==
== Description ==
*Annual, erect, monoecious herb, up to 100(–130) cm tall, much branched; stem terete or obtusely angular, glabrous or slightly pubescent, green or variably suffused with purple. *Leaves alternate, simple; stipules absent; petiole approximately as long as leaf-blade; blade ovate-lanceolate to rhomboid, 3.5–11 cm × 1–4.5 cm, acute and often slightly decurrent at base, obtuse, rounded or slightly retuse and often short mucronate at apex, entire, glabrous or slightly pubescent on veins when young. *Inflorescence consisting of dense clusters, lower ones axillary, higher ones often collected in an axillary and terminal spike which is often branched in its lower part; axillary clusters usually armed with (1–)2(–3) very sharp spines up to 2 cm long. *Flowers unisexual, solitary in the axil of a bract, subtended by 2 bracteoles; bracts and bracteoles scarious, mucronate from a broad base, shorter or as long as the perianth; male flowers usually arranged in a terminal spike above the base of the inflorescence, green; tepals 5 or in male flowers often 3, free, subequal, ovate-oblong to oblong-spatulate, up to 2.5 mm long, very convex, membranous, with transparent margins and green or purple median band; male flowers with 5 stamens about as long as tepals; female flowers with superior, oblong ovary, 1-celled, styles 2–3, ultimately recurved. *Fruit an oblong capsule with persisting styles, circumscissile a little below the middle or indehiscent, 1-seeded. *Seed about 1 mm in diameter, shiny black or brownish-black with thin margin. *Seedling with epigeal germination; cotyledons leafy, glabrous, apex rounded to slightly acute; hypocotyl up to 12 mm long, epicotyl absent.
''Amaranthus'' comprises about 70 species, of which about 40 are native to the Americas. It includes at least 17 species with edible leaves. It is almost impossible to make a distinction between ''Amaranthus spinosus'' and ''Amaranthus dubius'' Mart. ex Thell. based on morphological characters; ''Amaranthus spinosus'' has axillary spines which are not present in ''Amaranthus dubius''. However, spineless ''Amaranthus spinosus'' plants with 2''n'' = 34 have been observed in several localities. In Nigeria an ''Amaranthus dubius'' plant with 2''n'' = 32 has been recorded; this might be a spineless ''Amaranthus spinosus''. Other more or less reliable differences are the greater number of terminal male flowers in the inflorescences of ''Amaranthus spinosus'' and the smaller pores of the pollen.
Seeds mature about one month after flowering. They are scattered around the mother plants or distributed by animals feeding on the plants. It has been observed that large numbers of seedlings emerge from decaying cattle faecal deposits. Seeds are eaten by birds.
== Ecology ==
Spiny amaranth is a very noxious weed in many parts of the world. It is, for instance, troublesome in maize, cassava and groundnut in Ghana, in cotton in Mozambique, and in sugar cane in South Africa. In general, it is very common in roadsides, waste places, railway yards, cropped land and gardens, up to 1400 m altitude.
== Management ==
''Amaranthus spinosus'' is a host plant for, among others, tobacco mosaic virus, groundnut rosette virus, cucumber mosaic virus and root-knot nematodes (''Meloidogyne'' spp.), which attack some commercial crops. When the world’s worst weeds are ranked on the basis of the number of pests hosted, ''Amaranthus spinosus'' is placed number 6, hosting 15 pests that may affect crops. Some insects attacking ''Amaranthus spinosus'' have been recorded from Mexico: the pyralid ''Herpetogramma bipunctalis'' and the curculionid ''Conotrachelus seniculus''. These might be useful for biological control.
== Genetic resources ==
The genetic variability of ''Amaranthus spinosus'' is great because of its large area of distribution and its wide ecological adaptation. A collection of amaranths is kept at the Rodale Organic Gardening and Farming Research Center (OGFRC) at Kutztown, Pennsylvania, United States; South-East Asian accessions are kept at the Asian Vegetable Research and Development Center (AVRDC) at Tainan, Taiwan. African cultivars and introductions from OGFRC are kept at the National Horticultural Research Institute (NHR) in Nigeria and African cultivars at the AVRDC centre at Arusha, Tanzania. Indian collections are kept at the National Bureau of Plant Genetic Resources (NBPGR), New Delhi, India. Many national institutes have small working collections of local cultivars. Evaluation and variability studies are needed to reveal the amount of exploitable genetic variation.
== Prospects ==
== Author(s) ==
* P.C.M. Jansen , PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
== Correct citation of this article ==
Jansen, P.C.M., 2004. '''Amaranthus spinosus''' L. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.
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[[Category:PROTA]]
[[Category:Vegetables (PROTA)]]
