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Amaranthus rudis

(Common Waterhemp)

Common Names

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Common Names in English:

Common Waterhemp, Tall Amaranth

Description

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Genus Amaranthus

Herbs, usually annual , rarely perennial , monoecious (subg. Amaranthus and Albersia) or dioecious (subg. Acnida), glabrous or pubescent . Stems erect , ascending , decumbent , or prostrate , usually branched, occasionally simple or nearly so; without nodal spines (except in A. spinosus ). Leaves alternate, petiolate ; blade rhombic-ovate, ovate , obovate , spatulate , lanceolate, oblanceolate , or orbiculate to linear , base rounded to narrowly cuneate, margins usually entire, usually plane , slightly undulate , or crispate , rarely undulate-erose, apex acute, obtuse , or emarginate , usually mucronulate . Inflorescences terminal and/or axillary or exclusively terminal, compound dichasia arranged in spikes, thyrses , panicles, or glomerules ; components of terminal inflorescences often subtended by reduced leaves (pseudobracts), each dichasium unit subtended by persistent bracts. Bracts ovate, lanceolate, linear, subulate , deltate, or broadly triangular (in A. acanthochiton), or proximal bracts modified into spines (in A. spinosus) ; bracts of pistillate flowers not keeled (keeled in A. scleropoides and A. crassipes) ; bracteoles absent or 1-2. Flowers unisexual . Pistillate flowers: tepals absent or (1-) 3-5, distinct (connate in proximal 1/3 in A. polygonoides, equal or outer tepals larger than inner ones, usually membranaceous , sometimes scarious at maturity; stamens absent [rudimentary ]; pistil 1; ovule 1; style 0.1-1 mm, or absent; stigmas 2-3(-5), slender. Staminate flowers : tepals 3-5, equal or subequal ; stamens 3-5, filaments distinct, anthers 4-locular, pseudostaminodes absent; pistils absent or rudimentary. Utricles loosely enclosed by inner tepals, occasionally conspicuously 3(-5) -veined, usually globose , ovoid , or elongate-ovoid, thin walled, membranaceous, rugose or tuberculate , glabrous, dehiscence regularly circumscissile, irregularly dehiscent , or indehiscent. Seeds 1, subglobose or lenticular , usually smooth , shiny, sometimes indistinctly puncticulate or reticulate ; embryo annular . x = 16, 17.

Species ca. 70 (38 in the flora , including cultivated species) : mostly tropical , subtropical , and warm-temperate zones, some species in temperate zones; some taxa are at present almost worldwide as introduced and naturalized weeds .

Some segregate genera of Amaranthus, in the broad sense, have been proposed and sometimes recognized (see synonymy ). In the present treatment, Amaranthus is accepted in its broad sense. Three subgenera are currently recognized (S. L. Mosyakin and K . R. Robertson 1996) : subg. Acnida, subg. Amaranthus, and subg. Albersia.

Morphologic terminology in Amaranthus, as used in different floristic and taxonomic treatments, is rather confusing, especially regarding the terms applied to inflorescences and flowers. In the present treatment, we follow the traditional inflorescence terminology only for brevity and convenience; see T. A. Fedorova (1997) for a more complex scheme. A flower is subtended by a bract, often termed a "bracteole," and 0-2 lateral bracts, the true bracteoles. Structures that are clearly reduced green leaves subtending portions of the inflorescence are sometimes incorrectly called bracts.

Specimens of Amaranthus are often difficult to identify by someone not familiar with the group. When using the key , look closely at the tips of pistillate inflorescence branches for staminate flowers to determine whether the plant is monoecious or dioecious; this is especially important for some monoecious species that produce few staminate flowers. Also, pistillate plants of dioecious species are usually required for positive identification. Descriptions and measurements of floral parts are given in more detail for pistillate flowers, unless noted otherwise.

Determining the exact distribution of some species of Amaranthus in North America requires additional floristic and taxonomic studies. Because of the weedy life strategies of some Amaranthus species, they may occasionally occur as naturalized weeds or waifs very far from their original areas of distribution. Some of such isolated populations exist only as long as conditions are favorable and may eventually disappear or, vice versa, become expansive and invasive. These factors , together with frequent misidentifications in herbaria and the literature, obscure the distribution patterns of some Amaranthus species in North America. Weedy and introduced species of Amaranthus are often neglected or misidentified by collectors . Consequently, some taxa are known only from scattered localities in various regions of the flora, and their actual distribution may be much wider than present data indicate. Some species have been reported for the flora only as rare, casual , non-naturalized aliens , e.g. , on ballast , or as grain immigrants or wool contaminants, and may not now be present in North America. Because of all these factors, the maps and distribution statements in the treatment show the generalized distribution and may not properly reflect the actual changing distribution patterns of some species, especially those that have expanded their ranges over the decades due to various anthropic factors. In addition to the taxa discussed below, some other South American or Old World species may be found in North America in the future as introduced weeds.

Species of Amaranthus occasionally form interspecific hybrids. Such hybridization seems to be especially important and widespread in cultivated grain-amaranths, in wild representatives of the A. hybridus aggregate, between species of sect. Amaranthus, and between A. tuberculatus and species of sect. Amaranthus. The degree and scope of hybridization in Amaranthus are often overestimated, especially by European authors , and some taxa described as putative hybrids are in fact nonhybrid infraspecific forms of morphologically variable species. Hybrids between more distantly related species, if they occur at all, are usually highly sterile , such as hybrids between taxa of the subgenera Amaranthus and Acnida, or at least show much decreased fertility . There are no verified records of hybrids between representatives of the subgenera Amaranthus and Albersia.

Some species of Amaranthus are cultivated as pseudocereal and leaf-vegetable crops , or as ornamental or fodder plants (J. D. Sauer 1967; D. M. Brenner 1990; J. T. Williams and D. M. Brenner 1995; S. Cheatham et al. 1995). The most commonly cultivated taxa are A. caudatus Linnaeus, A. hypochondriacus Linnaeus, and A. cruentus Linnaeus of American origin , and south Asian A. tricolor Linnaeus. The cultivated species may occur occasionally as escapes near places of cultivation; they cannot be regarded as truly naturalized.

Species of Amaranthus were widely used by prehistoric and modern Native Americans as food, forage for livestock, medicinal plants, and, occasionally, for some other uses, such as face and body paint, ceremonial items, and fuel (S. Cheatham et al. 1995; D. E. Moerman 1998).[1]

Physical Description

Habit: Forb/herb

Biology

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Reproduction

Duration: Annual

Taxonomy

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Unambiguous Synonyms

  1. Acnida tamariscina auct. non (Nutt.) Wood
  2. Amaranthus tamariscinus auct. non Nutt.

Notes

Name Status: Accepted Name . Latest taxonomic scrutiny: 15-Mar-2000

Place of publication : Madroño 21:428. 1972

Name verified on 05-Feb-2002 by ARS Systematic Botanists. Last updated: 04-Feb-2003

Similar Species

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Members of the genus Amaranthus

ZipcodeZoo has pages for 402 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

A. abyssinicus · A. acanthobracteatus · A. acanthochiton (Green-Stripe Amaranth) · A. acroglochin · A. acutilobus (Sharplobe Amaranth) · A. adscendens · A. adulterinus · A. aeneus · A. aeruoides · A. affinis · A. albiflorus · A. albomarginatus · A. albus (Tumbleweed Amaranth) · A. alius · A. alopecurus · A. altissimus · A. A. caudatus (Love-Lies-Bleeding) · A. ambigens · A. amboinicus · A. anacardana · A. anardana · A. anderssoni · A. anderssonii · A. angustifolius · A. annectens · A. aragonensis · A. arardhanus · A. arctioideus · A. arenicola (Sandhills Amaranth) · A. artineanus · A. ascendens · A. ascendens subsp. polygonoides · A. asplundii · A. asplundii var. australis · A. ataco · A. atropurpureus · A. aureus · A. australis (Southern Water-Hemp) · A. bahiensis · A. batalleri · A. bellardi · A. berchtholdi · A. bernhardi · A. bicolor · A. bigelovii (Bigelow's Amaranth) · A. blitoides (Prostrate Amaranth) · A. blitum (Guernsey Pigweed) · A. blitum blitum (Purple Amaranth) · A. blitum emarginatus · A. blitum subsp. emarginatus · A. blitum subsp. oleraceus · A. blitum var. emarginatus · A. blitum var. graecizans · A. blitum var. nanus · A. blitum var. pseudogracilis (Amaranthus Blitum) · A. blitus · A. bouchoni · A. bouchonii · A. bracteosus · A. brandegei · A. brasiliensis · A. brisbanii · A. brownii (Brown's Amaranth) · A. buchtienianus · A. bullatus · A. californicus (Californian Amaranth) · A. campestris · A. canariensis · A. cannabinus (Tidal-Marsh Water-Hemp) · A. capensis · A. capensis subsp. uncinatus · A. capitatus · A. caracam · A. caracasanus · A. caracu · A. cararia · A. cararu · A. cardenasianus · A. carneus · A. carolinae · A. cathecu · A. caturus · A. caudadtus · A. caudatus (Love-Lies-Bleeding) · A. caudatus 'Atropurpurea' · A. caudatus caudatus (Love-Lies-Bleeding) · A. caudatus caudatus 'Atropurpureus' · A. caudatus 'Coral Fountain' · A. caudatus 'Dreadlocks' · A. caudatus 'Emerald Tassels' · A. caudatus 'Fat Spike' (Love-Lies-Bleeding) · A. caudatus 'Green Cascade' · A. caudatus 'Green Feathers' · A. caudatus 'Green Necklace' · A. caudatus 'Pony Tails' (Love-Lies-Bleeding) · A. caudatus subsp. saueri · A. caudatus 'Viridis' (Green Tassel Flower) · A. celosioides · A. cernuus · A. chihuahensis

More Info

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Further Reading

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal February 02, 2008:

Identifiers

Footnotes

  1. Sergei L. Mosyakin & Kenneth R. Robertson "Amaranthus". in Flora of North America Vol. 4 Page 405, 406, 410. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 7/1/2009