Monographs Details: Astragalus calycosus Torr. ex S.Watson
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Family:Fabaceae
Discussion:

337.  Astragalus calycosus

Low, sometimes dwarf or even diminutive, tufted, matted, or rarely mounded, essentially acaulescent, perennial, with a slender or at length stout and woody taproot and multicipital root-crown or closely forking caudex, densely strigulose throughout with straight, appressed, contiguous and parallel hairs up to 0.5-0.75 (1) mm. long, the herbage canescent or silvery, the vesture of the upper leaf-surface often turning a greenish-golden color when dried; stems 0, rarely up to 2 cm. long, the internodes then nearly always concealed by imbricated stipules; stipules 1.5-6 mm. long, submembranous becoming firmly papery, ovate or triangular, commonly obtuse, about semiamplexicaul; leaves 1—13 cm. long, with slender or filiform, rarely rather stiff, mostly recurved and subpersistent petioles and 1-13 obovate-cuneate, rhombic-obovate, oblanceolate, or elliptic, obtuse, acute, or exceptionally retuse leaflets 2-19 mm. long, when only 3 (as commonly) palmately trifoliolate, when more numerous usually crowded, the rachis mostly 1 cm. long or less, in one var. up to 4.5 cm. long; peduncles scapiform, mostly quite slender, 1-7 cm. long and weakly ascending or arcuately reclining in fruit, occasionally stiffer, erect or ascending even in fruit and up to 25 (30) cm. long; racemes loosely but usually shortly 1-8-, more rarely loosely 7-17-flowered, the flowers ascending or spreading, the axis usually less than 3 cm., rarely up to 7 cm. long in fruit; bracts scarious or early becoming so, ovate, 0.5-1.7 (2) mm. long; pedicels ascending, straight or a trifle arched outward, at anthesis 0.7-1.8 (2.5) mm. long, in fruit not or scarcely thickened, 1.1-3 (3.5) mm. long; bracteoles 0, rarely a minute scale; calyx 4.7—10.6 mm. long, densely strigulose with white and often some black hairs, the symmetric or decidedly oblique disc 0.7-1.1 mm. deep, the tube 3.7—6.4 (6.7) mm. long, 2.2—4.5 mm. in diameter, the erect or somewhat incurved, subulate or triangular teeth 0.5-3 (4.2) mm. long, the whole becoming papery, ruptured, marcescent; petals whitish (drying ochroleucous), flesh-color, milky-blue, pink, or bright purple, but the wing-tips always white or pallid and the keel-tip nearly always maculate, the banner (and sometimes other petals) tending to persist about the forming pod; banner recurved through ± 45°, rarely 90°, 9.5-16.5 (20.8) mm. long, variable in outline, mostly with cuneate claw abruptly expanded into an ovate, suborbicular, or obreniform blade 6-10 (13) mm. wide; wings slightly longer or shorter than the banner, 9-17 (19.7) mm. long, the claws 3.6-6.2 (7.2) mm., the blades (6.3) 7-12 (14) mm. long, through the proximal ?-¾ narrowly oblong or oblanceolate and 1.1-3.3 mm. wide, straight or slightly incurved, more or less dilated distally and cleft into 2 oblong or ovate, obtuse or subacute lobes (0.7) 1-4.5 mm. long, the lower (exterior) lobe commonly erect, the inner one usually broader and abruptly twisted inward toward the banner, the intervening sinus sometimes minutely appendaged; keel 7.4-11.6 (12.7) mm. long, the claws 3.5-6.2 (7.7) mm., the half-obovate or obliquely oblanceolate blades 4-6.7 mm. long, 2.1-3.2 (3.5) mm. wide, abruptly incurved through 85-100° to the rounded or bluntly deltoid apex; anthers 0.45—0.6 (0.7) mm. long; pod ascending (commonly humistrate), sessile, oblong-elliptic, linear-oblong, or lance-acuminate in profile, straight or gently lunate-incurved, (0.8) 1-2.1 (2.5) cm. long, (2.5) 3-4.5 mm. in diameter, rounded at base, cuspidate at apex, compressed-triquetrous with acute ventral and narrow but obtuse lateral angles, the plane or low-convex lateral faces broader than the narrowly grooved dorsal one, the thin, cinereously strigulose valves becoming papery, inflexed as a complete or nearly complete septum; seeds light or dark brown, sometimes nearly black, lustrous but irregularly pitted, 1.9-2.4 (2.8) mm. long.

The Torrey milk-vetch, A. calycosus, is a polymorphic species widely dispersed in the arid interior of western United States and is especially variable in habit of growth. Individual plants may form a diminutive tuft, or a depressed cushion up to 1.5 dm. in diameter, with 2-4-flowered racemes immersed in or barely projected beyond the foliage, but these common dwarf forms pass by gradual transition into a relatively robust, loosely tufted phase, with erect scapes and loose racemes of as many as seventeen flowers, the whole well over 2 dm. tall. The leaflets vary from one to thirteen to the leaf, the calyx from less than 5 mm. to over 10 mm. (with teeth 0.5-4 mm.) long, and the banner from less than 9 mm. to over 16 (very rarely over 20) mm. long. Segregates proposed and maintained on number of leaflets, number of flowers, length of calyx-teeth, or general growth-habit have no just claim to specific rank. The importance attached to length of the calyx-teeth, whether absolute or relative to the tube, has been overestimated. The pod, of the same form throughout the species, sens. lat., varies approximately between one and two centimeters long in each variety, and to nearly the same degree in many colonies of otherwise like plants. With evidence of instability in all the available differential characters, it has become increasingly difficult to define in mutually exclusive or exact terms the geographic varieties, which probably correspond to climactic points on a sliding scale of variation rather than to discrete entities.