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Astragalus cobrensis
Astragalus cobrensis A. Gray
Copper Mine Milkvetch
Fabaceae (Pea family)
Synonym(s):
USDA Symbol: ASCO5
USDA Native Status: L48 (N)
"Low, slender perennial, with a woody taproot and loosely forking, subterranean caudex, thinly strigulose to densely hirsutulous, the herbage green or cinereous, the leaflets ± bicolored, pallid beneath, yellowish-green and either glabrous or thinly pubescent above; stems few or several, decumbent and weakly ascending, (4) 6—20 (25) cm. long, subterranean for a space of 1.5—10 (15) cm., simple or bearing 1 (2) branches just above soil-level, flexuous or zigzag distally." (bibref: 1813).
"The Copper Mine milk-vetch, A. cobrensis, is a lowly, inconspicuous but nonetheless quietly elegant astragalus, often remarkable for the length of the buried caudex-branches which may be as long or longer than the aerial stems and are beset with prominent scaley stipule-sheaths. The habit of growth recalls the dwarfer, small-flowered Scytocarpi, although the strongly obcompressed and partly bilocular pod is characteristic of sect. Strigulosi. Like the related A. recurvus, with which it is marginally sympatric in central Arizona, A. cobrensis flowers in spring, and both species fluctuate in numbers and in vigor from year to year in response to depth of winter rainfall. Most other Strigulosi, whether native to the United States or Mexico, await the summer rains before starting into active growth, and the adaptation to vernal flowering may well be, with these two species, a reversion to the condition primitive in the genus." (bibref: 1813).
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Plant Characteristics
Duration: PerennialHabit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Stems few or several, decumbent and weakly ascending, (4) 6-20 (25) cm. long." (bibref: 1813).
Leaf: "Stipules 1.5-5 mm. long, those at the lowest, leafless nodes papery or early becoming so, connate into a low, loosely amplexicaul collar or shortly campanulate, bidentate sheath, the median and upper ones united through half their length or only at base, with triangular-lanceolate, thinly herbaceous, mostly erect blades; leaves 1.5- 8 (11) cm. long, shortly petioled or the uppermost subsessile, with (7) 11-19 (23) broadly obovate, obovate-cuneate, broadly oblong-elliptic, or suborbicular, retuse, flat leaflets (1.5) 3-12 (17) mm. long." (bibref: 1813).
Flower: Peduncles slender, incurved- ascending, (1) 1.5-8.5 cm. long, equaling or a little shorter than the leaf; racemes loosely (4) 8-22 (33)-flowered, the flowers spreading and ultimately declined, the axis elongating, (1) 2-6 (7.5) cm. long in fruit; bracts membranous, purplish, ovate or ovate-acuminate, 1-2.2 mm. long; pedicels slender, at anthesis ascending or arched outward, 1-2 mm. long, in fruit more strongly arched or deflexed, 1.3-2.5 (3) mm. long, persistent; bracteoles 0; calyx 3.2-4.5 mm. long, loosely strigulose with black or fuscous, and often a few intermingled white hairs, the slightly oblique saucer- or top-shaped disc 0.4-0.8 mm. deep, the campanulate or turbinate-campanulate tube 2.2-21 mm. long, 1.6-2.2 mm. in diameter, the subulate teeth 1-1.8 mm. long, the whole becoming papery, a little distended but unruptured; petals whitish tinged with dull lilac; banner at full anthesis recurved through about 85 degrees, broadly obovate-cuneate, -flabellate, or rhombic-ovate, deeply and widely notched, 6.5-7.8 mm. long, 4.2-5.8 mm. wide; wings a trifle longer or shorter than the banner, 6.2-1.1 mm. long, the claws 1.9-2.6 mm., the triangular- obovate, or broadly and obliquely elliptic, obtuse but erose or minutely undulate blades 4.2-5.9 mm. long, 1.7-3 mm. wide, the left one slightly incurved, the right abruptly bent inward at a right angle with the claw and its inner margin infolded; keel 4.4-6 mm. long, the claws 1.9-2.7 mm., the half-obovate or -circular blades 2.5-3.8 mm. long, 1.7-2.3 mm. wide, abruptly incurved through 95-100 degrees to the blunt, or sharply deltoid and obscurely porrect apex; anthers 0.3-0.55 mm. long." (bibref: 1813).
Fruit: "Pod pendulous, subsessile, the obscure stipe no longer than the calycine disc and often subobsolete, the body oblong- or somewhat clavate-ellipsoid, (7) 9-15 mm. long, 3.5-6 (reportedly "7") mm. in diameter, straight or a trifle arched downward, cuneate at base, abruptly contracted at apex into a very short, triangular, cuspidate beak, obcompressed, with low-convex ventral face obtusely carinate by the thick suture, flattened or widely and openly sulcate dorsally, the greenish, strigulose or villosulous valves becoming papery, stramineous, delicately cross- reticulate, inflexed as a partial or nearly complete septum 0.8-1.3 mm. wide; dehiscence apical and downward through the length of the ventral suture, the valves tending to twist outward in age; ovules 10-13; seeds brown, pitted and rugulose but somewhat lustrous, 2.4-3 mm. long." (bibref: 1813).
Bloom Information
Bloom Color: White , Purple , VioletBloom Time: Mar , Apr , May
Bloom Notes: "Petals whitish tinged with dull lilac." (bibref: 1813). "Mid-March to May, sometimes sporadically in fall. (bibref: 1813).
Distribution
USA: AZ , NMNative Distribution: As given for the varieties. (bibref: 1813).
Native Habitat: As given for the varieties. (bibref: 1813).
Bibliography
Bibref 1813 - Atlas of North American Astragalus (1964) Barneby, Rupert C.Search More Titles in Bibliography
Additional resources
USDA: Find Astragalus cobrensis in USDA PlantsFNA: Find Astragalus cobrensis in the Flora of North America (if available)
Google: Search Google for Astragalus cobrensis
Metadata
Record Modified: 2020-12-07Research By: Joseph A. Marcus