Monographs Details: Astragalus andersonii A.Gray
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:

351.  Astragalus Andersonii

Low, loosely tufted, with a woody taproot and shortly forking caudex, densely gray-villous throughout with fine, shorter and sinuous together with longer, almost straight, spreading or widely ascending hairs up to 1—1.3 mm. long, the stems more densely and shortly white-tomentose at base than distally; stems several or numerous, decumbent and incurved-ascending, (0.7) 1—2 dm. long, simple or bearing 1 spur or branchlet from a subbasal axil, commonly zigzag distally in age, stipules (1.5) 2-7 mm. long, the lowest early becoming scarious, amplexicaul and connate through half their length or less into a sheath (sometimes ruptured by the expanding stem), the upper ones connate at base only, or muted by a stipular line, or free, with lanceolate or triangular, erect, usually herbaceous blades; leaves (2) 3-10 cm. long, the lower ones petioled, the upper shortly so or subsessile, with (9) 13-21 mostly elliptic-oblanceolate and acute or abruptly short-acuminate, more rarely oval-obovate and mucronulate or obtuse, flat or loosely folded leaflets 3—10 (14) mm. long; peduncles erect or incurved-ascending, (2) 3-7 cm. long, either slightly longer or shorter than the leaf; racemes 12-20 (26)-flowered, rather dense at early anthesis, the flowers at first ascending, finally declined, the axis early elongating, 2.5-8 cm. long in fruit; bracts thinly herbaceous becoming scarious, narrowly lanceolate to linear-setaceous, 2-4 mm. long; pedicels at anthesis straight, ascending, 0.6-1 mm. long, in fruit usually arched outward, 1-1.7 mm. long, finally disjointing; bracteoles 0; calyx 6.2-8.2 mm. long, densely curly-villous, the subsymmetric disc 0.7-1 mm. deep, the campanulate tube 3.5-4.3 mm. long, 2.73.6 mm. in diameter, the subulate or subsetaceous teeth 2.4-4.3 mm. long, the whole becoming papery, ruptured, marcescent; petals whitish or ochroleucous, often tinged, and the banner veined, with dull lavender; banner recurved through ± 45°, ovate- or obovate-cuneate, 9.5-14.5 mm. long, 6.1-8 mm. wide; wings 8.8-13.5 mm. long, the claws 3.2-5 mm., the lunately oblong-elliptic, obtuse blades 6-9.5 mm. long, 2.2-3 mm. wide; keel 6.6-9 mm. long, the claws 3.2-4.8 mm., the half-obovate blades 3.6-4.8 mm. long, 2.2-2.9 mm. wide, abruptly incurved through 90-95° to the bluntly deltoid apex; anthers 0.45-0.55 mm. long; pod horizontally spreading or declined, sessile on a minute bosslike gynophore up to 0.5 mm. long, readily deciduous, the body obliquely oblong, linear-oblong, or narrowly lanceolate in profile, gently incurved or falcate, (1) 1.2-1.8 cm. long, 3-4.5 mm. in diameter, rounded at base, abruptly acute or sometimes tapering distally, cuspidate, strongly compressed-triquetrous, with low-convex or nearly flat lateral faces and shallowly sulcate dorsal face, carinate ventrally by the prominent suture, the thin, pale green, villous or villous-tomentulose valves becoming papery, stramineous, finely reticulate, inflexed as a complete or nearly complete septum 1.8-3 mm. wide; dehiscence primarily basal, after falling, ultimately through the ventral suture and the beak, the base of the valves curling back to release the seeds; ovules (10) 12-16; seeds brown or olivaceous, often purple-speckled, smooth or sparsely pitted, 1.9-2.8 (3.1) mm. long.—Collections: 50 (vi); representative: M. & G. Ownbey 2925 (CAS, NY, RSA, SMU, WS); Train 3612 (NA, NY); Ripley & Barneby 4461, 5821 (CAS, RSA).

Sandy flats, gravelly hillsides, and valley floors, in light dry soils overlying granites or more rarely basalt, 4300-7200 feet, locally plentiful in a narrow strip along the east base of the Sierra Nevada from Mono Lake, Mono County, California, north to the lower Carson and Truckee Valleys in western Nevada, reentering California in southern Lassen County.—Map No. 158.—April to June, or July at the greatest elevations.

Astragalus Andersonii (Charles Lewis Anderson, 1827-1910) Gray in Proc. Amer. Acad. 6: 524. 1864.—"Near Carson City, Nevada, Dr. C. L. Anderson (1863 and 1864)."—Cotypi, collected in 1863 and 1864, GH! isotypi (1864), MO, NY, P, US!—Tragacantha Andersonii (Gray) O. Kze., Rev. Gen. 943. 1891. Hamosa Andersonii (Gray) Rydb. in Bull. Torr. Club 54: 16. 1927.

In southern Washoe and Ormsby Counties, Nevada, the Anderson milk-vetch is a common and rather conspicuous element of the spring flora, easily distinguished from other astragali of the region by its connate stipules, gray-villous leaves, whitish or faintly lavender-tinged flowers, and declined, gently incurved, compressed-triquetrous pods which disjoint readily when ripe and dehisce by a somewhat elastic basal fracture on the ground. It is especially common between 4500 and 5500 feet around the east base of Mt. Rose and in the Truckee Valley upstream from Reno and extends northwest from there in a narrow belt, closely following the outer fringes of the Sierran pine forest, as far as Honey Lake. No record of its occurrence in Douglas or Lyon Counties has been seen and the stations in Mono County, where A. Andersonii reaches up to the 7000 feet contour and is decidedly rare, appear somewhat isolated. The Anderson milk-vetch is normally part of the sagebrush climax flora but is quick to colonize cleared and subsequently abandoned land, flourishing on grassy road embankments and in fallow fields. The species apparently affords a wholesome forage, for plants browsed down to the crown are often seen.