Astragalus canadensis
Sp. Pl. 2: 757. 1753.
Plants usually robust, rarely quite slender, (10–)15–120(–160) cm, strigose; from oblique or horizontal rhizomes. Stems usually erect, sometimes decumbent and ascending, green or purplish, fistulose when stout, 1–7+ cm underground, strigose. Leaves (3–)5–25(–35) cm; stipules 3–18 mm, membranous early becoming scarious; leaflets (7–)13–35, blades lanceolate, lanceolate-oblong, or elliptic, (5–)6–45(–52) mm, apex obtuse, apiculate, or truncate-emarginate, surfaces strigose, sometimes glabrous adaxially. Peduncles erect or incurved-ascending, (2.5–)4–22 cm. Racemes 20–100+-flowered, flowers spreading-declined; axis 2.5–16 cm in fruit; bracts 1.5–10 mm; bracteoles 0–2. Pedicels 1.2–3.5(–4) mm. Flowers 11.3–17(–17.5) mm; calyx short-cylindric, (4.6–)5.5–10.5(–11) mm, strigose or pilosulous, tube 4–8.5 mm, lobes subulate or triangular, 1.2–4.4(–5) mm; corolla ochroleucous, greenish white, or stramineous; keel (9.5–)10.2–13.6 mm. Legumes brown then blackish, straight or incurved, cylindroid, terete, (9–)10–20 × 2.9–5.2 mm, somewhat fleshy becoming stiffly papery or leathery, usually strigose, strigulose, glabrate, or glabrous, rarely puberulent; sessile or subsessile. Seeds (16–)18–26(–28).
Distribution
North America.
Discussion
Varieties 3 (3 in the flora).
The chromosome number of 2n = 16 is in harmony with the view that the alliance of Astragalus canadensis, along with its near relative A. oreganus, is with the Asiatic A. uliginosus Linnaeus. The relationship is sufficiently close that R. C. Barneby (1964) said of the Canada milkvetch, the New World’s most widely dispersed Astragalus, that taxonomy would most closely reflect biological realities if the New World forms were reduced to varietal status under a bicentrically dispersed A. uliginosus.
Selected References
None.
Lower Taxa
Key
| 1 | Legumes not grooved dorsally, usually glabrous, rarely puberulent or strigulose; distribution primarily eastern, extending westward to New Mexico, Utah, Idaho, British Columbia, and Northwest Territories. | Astragalus canadensis var. canadensis |
| 1 | Legumes grooved dorsally, strigose or glabrate; distribution largely intermontane, extending eastward to Black Hills of South Dakota. | > 2 |
| 2 | Stems (25–)30–70(–90) cm; calyx lobes (1.5–)2–4.4 mm, adaxial pair usually not much broader (though sometimes shorter) than the rest; legume beaks (3–)3.5–5 mm; forest belt of n Rocky Mountains (British Columbia southward to Oregon, eastward to Montana). | Astragalus canadensis var. mortonii |
| 2 | Stems (10–)15–55(–75) cm; calyx lobes 1–2.5(–3) mm, adaxial pair nearly always broadly triangular or deltate (and mostly shorter) than the rest; legume beaks 1.5–3 mm; sagebrush valleys, less commonly in meadows, and xeric pine forests (British Columbia southward to California, eastward to Colorado and Montana). | Astragalus canadensis var. brevidens |