Astragalus utahensis (Torr.) Torr. & A.Gray
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
"Shores and islands of the Salt Lake."—Holotypus, labeled "West shore of Great Salt Lake, June 24, 1850, Stansbury," NY! Stansbury collections at GH, K, are presumably isotypi!
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Synonyms
Phaca mollissima var. utahensis Torr., Tragacantha utahensis (Torr.) Kuntze, Xylophacos utahensis (Torr.) Rydb.
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Description
Species Description - Low, tufted, and subacaulescent or more commonly diffusely caulescent and loosely matted, with a taproot and shortly forking caudex, the stems and herbage densely pannose-tomentose with extremely fine, entangled, sinuous and curly hairs up to 1.5-2.5 mm. long, the cottony, not at all lustrous vesture concealing the surface of the white-felted leaflets; stems either very short and concealed by stipules, or more commonly developed, prostrate and radiating, up to 1.5 (2) dm. long, the internodes short, up to (but commonly less than) 3.5 cm. long; stipules membranous or early becoming so, ovate-triangular, ovate- or lance-acuminate, or -caudate, 3-10 mm. long, semiaxplexicaul-decurrent, dorsally tomentose but sometimes glabrescent distally; leaves (1.5) 3-12 cm. long, with flaccid, feebly persistent or deciduous petiole and (5) 9-19 broadly obovate, elliptic-obovate, or suborbicular, obtuse, rarely truncate-emarginate, exceptionally rhombic-ovate and acute, flat or loosely folded leaflets (2) 4-15 mm. long; peduncles rather stout, (1) 3-10 cm. long, equaling or shorter than the leaves, ascending at anthesis, prostrate in fruit; racemes shortly but loosely, sometimes subumbellately 2-8- flowered, the axis little elongating, 0.5-2.5 cm. long in fruit; bracts membranous, lanceolate, lance-, or, more rarely, ovate-acuminate, 4-9 mm. long; pedicels ascending, at anthesis 2-3 (3.7) mm., in fruit somewhat thickened, 2.3-4.3 mm. long; bracteoles commonly 0, rarely present and up to 1.5 mm. long; calyx (12) 13-17 mm. long, villous-tomentose like the herbage but more thinly so, the hairs white or partly fuscous, the obliquely campanulate or obconic disc 1-1.8 mm. deep, the membranous, purplish, broadly cylindric or at length tumid and then oblong-ellipsoid tube (8.5) 9.6-12.8 mm. long, 4.6-5.9 mm. in diameter, the firmer, subulate or lance-subulate teeth (2) 2.4-4 (4.7) mm. long; petals bright pink-purple, with a pale striate eye in banner; banner recurved through ± 45°, broadly oblanceolate or rhombic-spatulate, (21) 24-29 (31) mm. long, 10.5-15 (16.5) mm. wide; wings (19) 22-27 mm. long, the claws 11-14 (14.5) mm., the linear- or lance-oblong, obtuse, straight or slightly incurved blades 12-14.5 mm. long, 2.8-3.8 mm. wide; keel (16) 17-22 mm. long, the claws 11-14 mm., the lunate blades 7-8.9 mm. long, 3-3.9 mm. wide, gently incurved through 80-100° to the rounded apex; anthers 0.6-0.8 mm. long; pod ascending (humistrate), sessile on a glabrous, stipelike gynophore (1) 1.4-2.5 mm. long, the body (shorn of the vesture) lance-ellipsoid or narrowly ovoid-acuminate, 1.7-3 (3.5) cm. long, (5) 5.5—7.5 mm. in diameter, broadly cuneate or rounded at base, tapering gradually (rarely abruptly) into the erect or slightly incurved, laterally compressed beak, elsewhere obcompressed, openly and shallowly sulcate ventrally at and below the middle, a trifle sulcate or merely flattened dorsally, the thinly fleshy valves becoming stiffly papery or thinly leathery, reticulate, 0.2-0.3 mm. thick when ripe, so densely shaggy-villous with fine, horizontally spreading, lustrous, silky, cream- colored or pale yellow hairs 4-8 mm. long as to conceal the shape and surface of the fruit; dehiscence apical, tardy; ovules (22) 25-31; seeds light or dark brown, smooth or nearly so but scarcely lustrous, 2.1-3 mm. long.
Distribution and Ecology - Dry stony hillsides, open gravelly banks and river terraces, with sagebrush, oak brush, and junipers, 4100-7000 feet, especially abundant and vigorous on calcareous soils but not rare on other sedimentary and sometimes on granitic bedrock, common about Utah and Great Salt Lakes, Utah, south along the Sevier to Piute County, extending across the Wahsatch to the upper Price River and the edge of the Uinta Basin in Carbon and Duchesne Counties, north to the Bear River Valley in extreme southwestern Wyoming and to Bannock and Bear Lake Counties in southeastern Idaho; west through the limestone ranges of eastcentral Nevada to southern Eureka and northern Nye Counties—Map No. 88.—Late April to July, rarely again in fall.
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Discussion
The Utah milk-vetch was singled out by Jones as the state’s most beautiful flower; at very least it is one of the region’s most ornamental astragali. The generously proportioned and richly colored flowers are set off to advantage by the cottony tomentum of the foliage, and the pods, which so greatly excited the admiration of the early collectors on account of the dense silken vesture, are at once curious and handsome.
The relationship of A. utahensis to the A. Purshii complex is a close one. Early collections of A. Purshii var. concinnus, which superficially resembles the Utah milk-vetch in both foliage and flower, were long confused with it. The ordinarily fewer leaflets and the rigid, incurved pod of its species serve to distinguish var. concinnus, which has moreover a much more northern range than A. utahensis. The only form of A. Purshii found within the range of A. utahensis is var. Purshii, easily distinguished by its narrow leaflets and ochroleucous petals.
According to Stapf (in Curtis, Bot. Mag. Tab. 9302. 1933) the Utah milk-vetch was in English gardens about 1926, but it seems to have been lost to cultivation subsequently. The Argophylli are potentially perennial but are of rapid growth and short duration even in nature; under garden conditions they thrive only briefly and often fail to produce viable seed.
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Objects
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Distribution
Utah United States of America North America| Wyoming United States of America North America| Idaho United States of America North America| Nevada United States of America North America|