View source for Salix ×fragilis

{{Treatment/ID
|accepted_name=Salix ×fragilis
|accepted_authority=Linnaeus
|publications=
|basionyms=
|synonyms=
|hierarchy=Salicaceae;Salix;Salix subg. Salix;Salix sect. Salix;Salix ×fragilis
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Salicaceae]]</div><div class="higher-taxon"><small>genus</small>[[Salix]]</div><div class="higher-taxon"><small>subgenus</small>[[Salix subg. Salix]]</div><div class="higher-taxon"><small>section</small>[[Salix sect. Salix]]</div><div class="higher-taxon"><small>species</small>[[Salix ×fragilis]]</div></div>
|volume=Volume 7
|mention_page=page 28, 39, 43
|treatment_page=page 42
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Salix </b>×fragilis Linnaeus: The hybrid white willow, <i>S. alba</i> Linnaeus × <i>S. euxina</i> I. <b>Belyaeva</b>, a European introduction, is the most commonly cultivated and naturalized tree-willow in the flora area. <b>It</b> is characterized by: trees, 3–20 m, stems erect or drooping; branches highly brittle at base; petioles with spherical or foliaceous glands distally, pilose or villous adaxially; largest medial leaf blade amphistomatous, very narrowly elliptic or narrowly elliptic, margins uniformly serrate or serrulate, abaxial surface glaucous, both surfaces sparsely long-silky to glabrescent, adaxial surface slightly glossy or dull; juvenile leaves at first densely long-silky soon glabrous; pistillate bract deciduous after flowering; stamens 2; anthers yellow; pistillate adaxial nectary shorter than or equal to stipe; stipe 0.3–0.5 mm; ovary pyriform, glabrous; ovules 6–12 per ovary; styles 0.4–1 mm; capsules 4.5–6 mm; 2n = 57, 76.</span><!--

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|phenology=Flowering in late May–early June.
|elevation=0–2500m
|distribution=Alta.;B.C.;Man.;N.B.;Nfld. and Labr. (Nfld.);N.S.;Ont.;P.E.I.;Que.;Sask.;Alaska;Ariz.;Ark.;Calif.;Colo.;Conn.;Del.;D.C.;Ga.;Idaho;Ill.;Ind.;Iowa;Ky.;Maine;Md.;Mass.;Mich.;Minn.;Miss.;Mont.;Nebr.;Nev.;N.H.;N.J.;N.Mex.;N.Y.;Ohio;Oreg.;Pa.;R.I.;S.Dak.;Tenn.;Utah;Vt.;Va.;Wash.;W.Va.;Wis.;Wyo.
|discussion=<p>Individual trees can persist for years by trunk suckering and spread vegetatively by shoot fragmentation along stream margins, shingle and sand beaches, sedge meadows, hardwood forests, and sand pits.</p><!--
--><p>A study of <i>Salix ×fragilis</i> in Colorado (as S. ×rubens) showed that 2172 of 2175 trees were pistillate. Occasionally seed was set, possibly fertilized by <i>S. alba</i> (P. B. Shafroth et al. 1994). There are at least five clones of <i>S. ×fragilis</i> (as S. ×rubens) in cultivation (T. Berg in B. Jonsell and T. Karlsson 2000+, vol. 1); the pistillate are sterile but the staminate produce viable pollen. The hybrid plants are often misidentified as S. “fragilis” or as <i>S. nigra</i>. In the flora area, reproduction of the hybrid seems to be mainly by stem fragmentation.</p><!--
--><p>Prior to the lectotypification of <i>Salix</i> fragilis Linnaeus and the description of <i>S. euxina</i> (I. V. Belyaeva 2009), the name S. “fragilis” was often inadvertently used for both the pure species and for its hybrids with <i>S. alba</i>. Thus all herbarium specimens under the names “fragilis” and “×rubens” need to be revised.</p><!--
--><p><i>Salix ×fragilis</i> can be separated from <i>S. euxina</i> by having branches and branchlets hairy or glabrescent in age versus glabrous; leaf blades not glaucous abaxially versus glaucous; leaves amphistomatous versus hypostomatous or with stomata only along veins and at apex; and pistillate catkins slender and loosely flowered versus stout and moderately densely flowered.</p><!--
--><p>Several molecular studies have been designed to understand the nature of this hybrid. H. Beissmann et al. (1997), using AFLP markers, were able to recognize three clusters: <i>Salix alba</i>, <i>S. euxina</i> (as <i>S. fragilis</i>), and <i>S. ×fragilis</i> (as S. ×rubens); but a study by K. De Cock et al. (2003), also using AFLP markers, was unable to resolve <i>S. alba</i> and <i>S. ×fragilis</i> (as S. ×rubens). They recommended the use of experimental hybridization to study the genesis of this hybrid. Molecular and genetic studies by L. L. Triest (2001) and coworkers concluded that in modern open agricultural situations in Belgium, hybridization was of low occurrence, and that morphologically intermediate plants were not necessarily genetically intermediate. These studies saw different facets of the question. Clearly there are three entities, <i>S. alba</i>, <i>S. euxina</i>, and their hybrid but, because <i>S. euxina</i> may be rare outside of cultivation, natural hybridization may not occur and the question of whether <i>S. ×fragilis</i> can be backcrossed with <i>S. alba</i> remains to be studied. The specimens used in these molecular studies require reidentification.</p>
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|references=
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-->{{#Taxon:
name=Salix ×fragilis
|author=
|authority=Linnaeus
|rank=species
|parent rank=section
|synonyms=
|basionyms=
|family=Salicaceae
|phenology=Flowering in late May–early June.
|elevation=0–2500m
|distribution=Alta.;B.C.;Man.;N.B.;Nfld. and Labr. (Nfld.);N.S.;Ont.;P.E.I.;Que.;Sask.;Alaska;Ariz.;Ark.;Calif.;Colo.;Conn.;Del.;D.C.;Ga.;Idaho;Ill.;Ind.;Iowa;Ky.;Maine;Md.;Mass.;Mich.;Minn.;Miss.;Mont.;Nebr.;Nev.;N.H.;N.J.;N.Mex.;N.Y.;Ohio;Oreg.;Pa.;R.I.;S.Dak.;Tenn.;Utah;Vt.;Va.;Wash.;W.Va.;Wis.;Wyo.
|introduced=true
|reference=None
|publication title=
|publication year=
|special status=
|source xml=https://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/f6b125a955440c0872999024f038d74684f65921/coarse_grained_fna_xml/V7/V7_1320.xml
|genus=Salix
|subgenus=Salix subg. Salix
|section=Salix sect. Salix
|species=Salix ×fragilis
}}<!--

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