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Astragalus desperatus var. desperatus

Astragalus desperatus M.E. Jones var. desperatus

Rimrock Milkvetch

Fabaceae (Pea family)

Synonym(s):

USDA Symbol: ASDED

USDA Native Status: L48 (N)

"Dwarf, tufted, subacaulescent and shortly caulescent perennial, with woody taproot and at length shortly forking suffruticulose caudex often beset with a thatch of wiry, persistent but not spinose petioles, strigulose, strigose-hirsutulous, or loosely strigose with straight or largely straight and appressed or often some (especially toward the inflorescence, and late in the season elsewhere) or even mostly ascending hairs up to 0.5-0.95 (1.3) mm. long, the herbage greenish- cinereous or silvery-canescent, the leaflets pubescent on both sides but thinly so or medially glabrescent above; stems almost 0 or up to 3 (8) cm. long, when developed prostrate, the internodes often all concealed by loosely imbricated stipules, even when developed short, up to 6 (8) mm. long, mostly less; stipules submembranous early becoming papery-scarious, ovate to broadly lanceolate, (1.5) 2-7 mm. long, semi- or the early ones fully amplexicaul, the lowest sometimes very shortly and obscurely connate (but less connate than adnate); leaves (1) 1.5-7 (9) cm. long, slender-petioled, with (3) 7-15 (17) well-separated or rarely crowded, oblanceolate, obovate, or elliptic, obtuse or subacute, commonly folded leaflets 2-11 (13) mm. long, all readily deciduous when dry; peduncles usually quite slender, erect and ascending at anthesis, reclinate in fruit, 1-9 cm. long, much shorter, equaling, or a little longer than the leaf; racemes loosely but sometimes very shortly (3) 4-14-flowered, the flowers at first ascending, spreading or declined in age, the axis scarcely or considerably elongating, 0.4-7 cm. long in fruit; bracts papery-membranous, ovate-acuminate or lanceolate, (1) 1.5-5 mm. long; pedicels at anthesis ascending, 0.5-1 (1.2) mm. long, in fruit arched outward, thickened but ultimately disjointing, 0.5—1.4 (2) mm. long; bracteoles usually 0, rarely 1 or 2; calyx 3.5—9.4 mm. long, loosely strigulose with white and often some black hairs, the subsymmetric disc 0.5—1.4 mm. deep, the membranous, purplish tube varying from campanulate to cylindric, the subulate teeth 0.8—2.4 mm. long; petals pink-purple or lilac-pink, drying violet or bluish, the wing-tips sometimes pallid or white; banner recurved through ± 45°, obovate-cuneate or broadly oblanceolate, shallowly notched, 7.4—14.5 mm. long; wings a little shorter, the straight or slightly incurved blades obtuse or emarginate at apex; keel 5.9—12.5 mm. long, the half-obovate blades incurved through 90—115° to the rounded apex; anthers 0.4—0.7 mm. long; pod strongly declined or deflexed (but the tip often incurved to erect), sessile on and readily disjointing from a conical receptacle or incipient gynophore up to 1.2 mm. long, obliquely ovoid, oblong-, or lance-ellipsoid, lunately to very strongly incurved through 1/10—3/4, rarely an almost complete circle, 6—19 mm. long, 3—6 mm. in diameter, obtuse or retuse at base, contracted distally into a cuneate to broadly deltoid, laterally compressed, commonly incurved beak, elsewhere more or less strongly dorsiventrally compressed, carinate ventrally by the thin, prominent (but proximally often depressed) suture, openly sulcate dorsally, the thin, green but nearly always red-mottled or -spotted valves becoming papery, stramineous, delicately cross-reticulate, hirsute with lustrous, loosely ascending or horizontal, more or less twisted hairs seated on a minute bulbous thickening, not inflexed or inflexed as a very narrow partial septum up to 1 mm. wide; dehiscence apical and downward through the ventral suture, the beak widely gaping; ovules 16-28, commonly 18-24; seeds brown or greenish, often purple- speckled, pitted or wrinkled but somewhat lustrous, 2—2.9 mm. long." (bibref: 1813).

"The rimrock milk-vetch, A. desperatus, is one of quite few astragali in which a mutation has occurred involving the size and relative proportions of the calyx and petals, with scarcely any change readily apparent in other organs. The easily distinguished varieties are found in identical environments and are not mutually exclusive in range, phenomena again unusual in the genus." (bibref: 1813). "he common form of the rimrock milk-vetch, var. desperatus, is a neat little plant, notable for its tufted growth-habit, slender, wiry petioles from which the leaflets disjoint readily when dry, subscapose peduncles, and especially the small, deflexed, commonly much incurved, nearly always gaily mottled pod of papery texture beset with long, spreading, lustrous hairs minutely but always perceptibly enlarged at base. The small flowers are commonly bicolored, the white or pallid wing-tips contrasting with a purple banner and keel. The species is very characteristic of the sandstone butte and badland country of the Colorado Basin. It is usually found where its eventually woody taproot can strike down into a crevice of sandstone bedrock, thus often on rock pavement or on detrital slopes under cliffs with only a thin mantle of clay or wind-blown sand masking the rocky nature of the subsurface materials. The flowers vary somewhat in size; there is a series of variants connecting the small-flowered extreme exemplified by the typus of var. petrophilus with a normal or average state." (bibref: 1813).