View source for Amaranthus retroflexus

{{Treatment/ID
|accepted_name=Amaranthus retroflexus
|accepted_authority=Linnaeus
|publications={{Treatment/Publication
|title=Sp. Pl.
|place=2: 991. 1753
|year=1753
}}
|common_names=Redroot pigweed;redroot amaranth;wild-beet amaranth;rough pigweed;common amaranth
|basionyms=
|synonyms={{Treatment/ID/Synonym
|name=Amaranthus retroflexus var. salicifolius
|authority=I. M. Johnston
|rank=variety
}}
|hierarchy=Amaranthaceae;Amaranthus;Amaranthus subg. Amaranthus;Amaranthus retroflexus
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Amaranthaceae]]</div><div class="higher-taxon"><small>genus</small>[[Amaranthus]]</div><div class="higher-taxon"><small>subgenus</small>[[Amaranthus subg. Amaranthus]]</div><div class="higher-taxon"><small>species</small>[[Amaranthus retroflexus]]</div></div>
|volume=Volume 4
|mention_page=page 422
|treatment_page=
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Plants </b>densely to moderately pubescent, especially distal parts of stem and branches. <b>Stems</b> erect, reddish near base, branched in distal part to simple 0.2–1.5(–2) m; underdeveloped or damaged plants rarely ascending to nearly prostrate. <b>Leaves</b>: petiole 1/2 to equaling blade; blade ovate to rhombic-ovate, 2–15 × 1–7 cm, base cuneate to rounded-cuneate, margins entire, plane or slightly undulate, apex acute, obtuse, or slightly emarginate, with terminal mucro. <b>Inflorescences</b> terminal and axillary, erect or reflexed at tip, green or silvery green, often with reddish or yellowish tint, branched, leafless at least distally, usually short and thick. <b>Bracts</b> lanceolate to subulate, (2.5–)3.5–5(–6) mm, exceeding tepals, apex acuminate with excurrent midrib. <b>Pistillate</b> flowers: tepals 5, spatulate-obovate, lanceolate-spatulate, not clawed, subequal or unequal, (2–)2.5–3.5(–4) mm, membranaceous, apex emarginate or obtuse, with mucro; style branches erect or slightly spreading,; stigmas 3. <b>Staminate</b> flowers few at tips of inflorescences; tepals 5; stamens (3–)4–5. <b>Utricles</b> broadly obovoid to broadly elliptic, 1.5–2.5 mm, shorter than or subequal to tepals, smooth or slightly rugose, especially near base and in distal part, dehiscence regularly circumscissile. <b>Seeds</b> black to dark reddish brown, lenticular to subglobose-lenticular, 1–1.3 mm, smooth, shiny.</span><!--

-->{{Treatment/Body
|phenology=Flowering summer–fall.
|habitat=Banks of rivers, lakes, and streams, disturbed habitats, agricultural fields, railroads, roadsides, waste areas
|elevation=0-2500 m
|distribution=St. Pierre and Miquelon;Alta.;B.C.;Man.;N.B.;Nfld. and Labr.;N.W.T.;N.S.;Nunavut;Ont.;P.E.I.;Que.;Sask.;Ala.;Alaska;Ariz.;Ark.;Calif.;Colo.;Conn.;Del.;D.C.;Fla.;Ga.;Idaho;Ill.;Ind.;Iowa;Kans.;Ky.;La.;Maine;Md.;Mass.;Mich.;Minn.;Miss.;Mo.;Mont.;Nebr.;Nev.;N.H.;N.J.;N.Mex.;N.Y.;N.C.;N.Dak.;Ohio;Okla.;Oreg.;Pa.;R.I.;S.C.;S.Dak.;Tenn.;Tex.;Utah;Vt.;Va.;Wash.;W.Va.;Wis.;Wyo.;introduced and naturalized nearly worldwide.
|discussion=<p><i>Amaranthus retroflexus</i>, native to central and eastern North America, is a successful invasive species and has effectively colonized a wide range of habitats on all inhabited continents. Its variability is extremely wide; usually the species is easily recognized and its identification causes no specific problems. Infraspecific entities described within <i>A. retroflexus</i> are mostly ecologic variants of little or no taxonomic value. Two varieties are more easily recognized: the common var. retroflexus, with bracts about 1.5–2 times as long as tepals, and a more rare var. delilei (Richter & Loret) Thellung (= A. delilei Richter & Loret), with bracts 1–1.5 times as long as tepals.</p><!--
--><p>Occasional forms morphologically intermediate between <i>Amaranthus retroflexus</i> and taxa of the <i>A. hybridus</i> aggregate (e.g., <i>A. powellii</i> and <i>A. hybridus</i>, in the strict sense) are known both in the Americas and the Old World. Usually such plants are treated as hybrids; in many cases they are probably just extremes of the natural variability of <i>A. retroflexus</i>. Putative hybrids of <i>A. retroflexus</i> were described from Europe as A. ×ozanonii Thellung (<i>A. hybridus</i> × <i>A. retroflexus</i>) and A. ×soproniensis Priszter & Karpáti (<i>A. powellii</i> × <i>A. retroflexus</i>) (see A. Thellung 1914–1919; S. Priszter 1958; P. Aellen 1959; F. Grüll and S. Priszter 1973).</p>
|tables=
|references=
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-->{{#Taxon:
name=Amaranthus retroflexus
|authority=Linnaeus
|rank=species
|parent rank=subgenus
|synonyms=Amaranthus retroflexus var. salicifolius
|basionyms=
|family=Amaranthaceae
|phenology=Flowering summer–fall.
|habitat=Banks of rivers, lakes, and streams, disturbed habitats, agricultural fields, railroads, roadsides, waste areas
|elevation=0-2500 m
|distribution=St. Pierre and Miquelon;Alta.;B.C.;Man.;N.B.;Nfld. and Labr.;N.W.T.;N.S.;Nunavut;Ont.;P.E.I.;Que.;Sask.;Ala.;Alaska;Ariz.;Ark.;Calif.;Colo.;Conn.;Del.;D.C.;Fla.;Ga.;Idaho;Ill.;Ind.;Iowa;Kans.;Ky.;La.;Maine;Md.;Mass.;Mich.;Minn.;Miss.;Mo.;Mont.;Nebr.;Nev.;N.H.;N.J.;N.Mex.;N.Y.;N.C.;N.Dak.;Ohio;Okla.;Oreg.;Pa.;R.I.;S.C.;S.Dak.;Tenn.;Tex.;Utah;Vt.;Va.;Wash.;W.Va.;Wis.;Wyo.;introduced and naturalized nearly worldwide.
|reference=None
|publication title=Sp. Pl.
|publication year=1753
|special status=
|source xml=https://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/f50eec43f223ca0e34566be0b046453a0960e173/coarse_grained_fna_xml/V4/V4_824.xml
|genus=Amaranthus
|subgenus=Amaranthus subg. Amaranthus
|species=Amaranthus retroflexus
}}<!--

-->[[Category:Treatment]][[Category:Amaranthus subg. Amaranthus]]