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FNA | Family List | FNA Vol. 5 | Polygonaceae | Eriogonum

133. Eriogonum flavum Nuttall, Cat. Pl. Upper Louisiana. no. 34. 1813.

Eriogonum flavum var. polyphyllum (Small ex Rydberg) M. E. Jones; E. polyphyllum Small ex Rydberg

Herbs, matted, 0.2-4 × 1-10 dm, tomentose to floccose. Stems: caudex absent or spreading; aerial flowering stems erect or nearly so, slender, solid, not fistulose, arising at nodes of caudex branches and at distal nodes of short, nonflowering aerial branches, (0.1-)0.5-2(-3) dm, tomentose to floccose. Leaves basal, occasionally in rosettes; petiole 0.5-4 cm, tomentose to floccose; blade linear-oblanceolate to oblong or elliptic, 1-7(-9) × (0.3-)0.5-1.5 cm, densely whitish- or grayish-tomentose abaxially, mostly tomentose to floccose or glabrous and green adaxially, margins entire, plane. Inflorescences subcapitate or umbellate, 0.5-3(-5) × 0.3-2.5(-3) dm; branches tomentose to floccose; bracts 4-6, leaflike to semileaflike at proximal node, 0.5-2 × 0.2-0.5 cm, sometimes absent immediately below involucre. Involucres 1 per node, turbinate to campanulate, 3-9 × 2-5 mm, tomentose to floccose; teeth 5-8, erect, 0.2-1 mm. Flowers 3-7 mm, including 0.2-1.5 mm stipelike base; perianth pale to bright yellow, densely pubescent abaxially; tepals monomorphic, oblong; stamens exserted, 3-6 mm; filaments pilose proximally. Achenes light brown to brown, 3-5 mm, glabrous except for sparsely pubescent beak.

Varieties 3 (3 in the flora): w North America.

Eriogonum flavum approaches E. arcuatum morphologically in southeastern Wyoming, and a clear distinction is not always possible when the plants are immature or the herbarium material is poor.

Variety polyphyllum, as traditionally circumscribed, is an alpine phase of both var. flavum and var. piperi; it is encountered infrequently in scattered range in the high mountains of southwestern Montana and northwestern Wyoming.

1 Stipelike bases of flowers 1-1.5 mm; usually w of Continental Divide; sw Alberta and British Columbia, n Idaho, w Montana, ne Oregon, e Washington, nw Wyoming   133c var. piperi
+ Stipelike bases of flowers 0.2-1 mm; usually e of Continental Divide; ec Alaska, s Alberta, sw Manitoba, s Saskatchewan, wc Yukon, Montana, w Nebraska, North Dakota, South Dakota, e Wyoming, and Colorado   (2)
2 (1) Leaf blades (0.3-)1-1.5 cm wide; inflorescence branches 4-20 cm; s Alberta, sw Manitoba, s Saskatchewan, Montana, w Nebraska, North Dakota, South Dakota, e Wyoming, and Colorado   133a var. flavum
+ Leaf blades 0.4-1 cm wide; inflorescence branches 0.5-2 cm; ec Alaska, wc Yukon   133b var. aquilinum


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