Monographs Details: Astragalus gilensis Greene
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:

308.  Astragalus gilensis

Acaulescent or nearly so, the leaves tufted on a multicipital root-crown or shortly forking caudex beset with a thatch of marcescent, closely imbricated, brownish stipules, the herbage silvery-strigulose (strigose) with appressed and often a few narrowly ascending hairs up to 0.5—1.1 mm. long, the leaflets equally pubescent on both sides; stipules submembranous becoming papery, 4—9 mm. long, the erect, ovate or broadly lanceolate blades densely pubescent dorsally; leaves (1.5) 2.5-9 cm. long, with slender petioles and (7) 11-21 (25) elliptic, oblong-elliptic, or oblanceolate and acute, more rarely oval-elliptic and obtuse or emarginate, flat or loosely tufted leaflets (2) 3-12 mm. long; peduncles (2.5) 3.5-15 cm. long, mostly surpassing the leaves, at anthesis incurved-ascending, arcuate-reclinate or prostrate and radiating in fruit; racemes densely 7-26-flowered, the upper flowers ascending, the lower ones spreading or declined, together forming a subcapitate cluster or oblong-ovoid head, the axis scarcely elongating, 0.5—2.5 cm. long in fruit; bracts submembranous, lanceolate, 1.5-4 mm. long; pedicels either straight and ascending or a little arched outward, 0.6—1.5 mm. long, a trifle thickened but scarcely longer in fruit; bracteoles 0—2; calyx 3.7—6 mm. long, strigulose with white or mixed black and white hairs, the slightly oblique disc 0.4-0.9 mm. deep, the tube 2.3-4 mm. long, 1.6-2.4 mm. in diameter, the erect, subulate teeth 1.3-2.7 mm. long, the whole becoming papery, ruptured, marcescent; petals varying from flesh-pink to pink-purple with white wing-tips; banner recurved through 45-50°, elliptic or elliptic-oblanceolate, shallowly notched, 6.2-10.4 mm. long, (2.8) 3-5.6 mm. wide; wings 5.8-9 mm. long, the claws 2.1-3.9 mm., the oblong-oblanceolate or elliptic, obtuse or emarginate blades (3.7) 4-6.2 mm. long, 1.4-2.7 mm. wide, both incurved but the left more strongly so and its inner margin infolded; keel 4.3-6.8 mm. long, the claws 2.2-3.6 mm., the half-circular or -obovate blades 2.5-3.6 mm. long, 1.5-2.2 mm. wide, abruptly incurved through 95-120° to the blunt, deltoid, sometimes minutely porrect apex; anthers 0.3-0.5 (0.55) mm. long; pods ascending or spreading according to their position in the crowded, globose or oblong fruiting head, obliquely ovoid or oblong-ellipsoid, 4.5-7.5 mm. long, 2-4.2 mm. in diameter, rounded or shortly obconic at base, abruptly contracted distally into a declined, cusplike beak 0.5—1.2 mm. long, keeled ventrally by the thick, prominent, convexly arched suture, at once obscurely trigonous and a trifle laterally compressed, the convex lateral faces wider than the flattened or shallowly grooved dorsal one, the decidedly fleshy and firm, red- dish-tinged, strigulose valves becoming brownish, stiffly papery or almost leathery, faintly cross-reticulate; ovules 7—11, commonly 8; seeds ocher, purplish-brown, or brown blotched with purple, obscurely pitted or smooth but scarcely lustrous, 1.4-2 mm. long.—Collections: 22 (vi); representative: Metcalfe 1553 (CAS, NY, NMC); Barneby 12,615 (CAS, RSA); Eggleston 20,255, 20,274 (NY); Ripley & Barneby 5094 (RSA).

Dry sandy or gravelly flats, knolls and benches in xeric pine forest, 5600-8600 feet, locally plentiful in scattered stations in the Mogollon mountain system about the headwaters of the Little Colorado and Gila Rivers, from southern Navajo County, Arizona, southeast to western Sierra and northern Grant Counties, New Mexico; apparently somewhat isolated to the northeast on the Jemez Mountains, Sandoval County, New Mexico.—Map No. 140.—(April) May to September.

Astragalus gilensis (of Gila River) Greene in Bull. Torr. Club 8: 97. 1881 ("Gilensis"). —"On a high summit at the mouth of the canyon of the Gila River. April, 1881."—Holotypus, labeled in Greene’s hand and with additional datum in pencil: "No. 1553," but without date or locality, ND (Herb. Greene. No. 31,089)1 isotypi, collected April 3, 1881, CAS, GH, MO!—The Greene spms. at K, dated April 30, and ex herb. Porter, at PH, although dated 1880, are probably other isotypi.—Batidophaca gilensis (Greene) Rydb. in N. Amer. Fl. 24: 318. 1929.

The Gila milk-vetch is a sharply defined and stable species, its silvery dolabriform vesture, slender, relatively long, scapose peduncles bearing dense heads of pinkish or purple and white flowers, and its small, crowded pods of characteristic form and compression all contributing to an idiosyncratic facies. The species most like it in general organization and habit of growth is the related A. troglodytus, but this is readily distinguished by its hirsute inflorescence and pod and its larger, reddish-purple flower. The species has been collected in flower and fruit in every month from April to September. In cultivation it has flowered continuously through the summer, but in its natural habitat the period of abundant flower usually follows summer rains and the spring crop of fruits is small and uncertain.