Flora of the Canadian Arctic Archipelago

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S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Astragalus L.

English: Milk-vetch.

Fabaceae (Leguminosae), Pea family.

Published in Sp. Pl. 755. 1753.

Vegetative morphology. Plants 2–30 cm high; perennial herbs; not caespitose. Taproot present. Well developed on older plants. Ground level or underground stems horizontal; rhizomatous; elongate; 0.4–0.8 mm wide. Ground level or underground stems scales absent (stipules present). Caudex present. Aerial stems branching from a tap at or near ground level into two or more branches; erect, or decumbent. Aerial stem trichomes spreading. Leaves distributed along the stems; alternate, or opposite (compact plants of Astragalus alpinus have leaves that may appear opposite); dying annually and non-persistent (leaf blades), or marcescent (petioles). Stipules present; persisting for 2 or more years; 3–6 mm long; 2–4 mm wide; sheathing, or not sheathing; black from hairs (when young), or brown (with age), or green; hairy (when young, glabrescent); apex acute, or rounded. Petioles 5–35 mm long; hairy; pilose, or villous. Petiole hairs shorter than the diameter of the petiole, or longer than the diameter of the petiole; appressed, or spreading, or erect; straight; smooth (flattened, whitish, approaching strigose). Leaf blades compound. Blades 15–55 mm long, 8–25 mm wide, spreading, veins pinnate or appearing single-veined or with inconspicuous veins. Blade adaxial surface glabrous or glabrescent or hairy, hairs pubescent or pilose or strigose, hairs simple (if applicable), hairs sparse or moderately dense or dense, hairs white, or translucent. Blade abaxial surface glabrous or hairy, hairs pubescent or villous or short-silky or long-silky or strigose, hairs sparse or moderately dense or very dense, hairs white, hairs straight or wavy, hairs appressed or spreading. Blade apices acute, or obtuse, or rounded. Leaflet arrangement pinnate (odd-pinnate). Leaflets 7–23; 3–12 mm long; 1–4.5 mm wide; linear, or oblong, or elliptic, or ovate, or lanceolate; veins conspicuous, or veins inconspicuous.

Reproductive morphology. Flowering stems about as high as the leaves, or conspicuously taller than the leaves; without leaves. Flowering stems hairy. Flowering stems pilose, or strigose. Flowering stem hairs simple; white or translucent and black. Inflorescences racemose; terminal; dense (in flower); oblong, or globose or sub-globose; 0.5–9 cm long; 10–35 mm wide; elongating as the fruit matures, or not elongating as the fruit matures. Bisexual spike(s) with empty bracts at the base (stipule-like). Flowers per inflorescence 3–16; medium-sized, or large; bilaterally symmetrical (zygomorphic). Sepals conventional; 5; fused; 4–6 mm wide; brown, or black. Calyx tubular, or funnel-form; 5-lobed; hairy. Calyx hairs pilose, or strigose; black, or black and white or translucent. Calyx teeth equal or nearly so; 0.9–1.6 mm long. Petals conventional; both free and fused; 5; green, or white, or purple, or blue; with contrasting markings, or without contrasting markings; unlobed, or slightly lobed or undulating; 6–15 mm long. Corolla papilionaceous; keel blunt. Stamens 10; stamen filaments all equal in length (or slightly unequal). Anther filaments 9 fused into a tube, plus 1 free. Anthers yellow; 0.3–0.5 mm long. Nectaries present. Ovary superior; carpels 1; monomerous. Stipes 0–8 mm long (in fruit). Stigmas per ovary 1. Ovules per ovary 3–12. Fruit stalked; with calyx persisting; dry; a legume; spherical (almost), or ellipsoid, or ovoid; black, or brown, or red; 5–26 mm long; 2.5–6 mm wide; glabrous, or hairy; distinctly flattened, or not distinctly flattened; dehiscent; splitting to the base into separate segments. Legume nearly 2-locular by intrusion of placenta; valves straight. Styles persisting but not modified. Seeds 3–12; 1–2 mm long; brown, or yellowish; surfaces smooth.

Chromosome information. 2n = 16, or 32, or 48.

Ecology and habitat. Substrates: imperfectly drained moist areas, dry, moderately well-drained areas; acidic, or calcareous. Dry or moist sandy areas.

General notes. The name Astragalus is from the Greek for ankle bone, used in ancient times as a form of dice. It has been supposed that the word was applied to the plant because of the rattle of seeds within the dry pods of some species.

Illustrations. • Stipules of Astragalus leaves. Left, Astragalus eucosmus leaf conspicuously larger than A. alpinus (the two leaves to the right). Note stipules at the base of the petioles. Photograph by Kathy Thornhill 2005.


This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.

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