Monographs Details: Astragalus succumbens Douglas ex Hook.
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:

336.  Astragalus succumbens

Low but robust, densely to rather thinly hirsute or hirsutulous nearly throughout with rather stiff, spreading and ascending or somewhat retrorse hairs up to 0.7-1.3 mm. long, the herbage greenish or canescent, the leaflets bicolored, brighter green and sometimes glabrous or medially glabrescent above; stems several, (1) 1.5-4 dm. long, arising together from the root-crown shortly below soil-level, the inner ones erect, the outer longer and ascending, together forming flat-topped, bushy plants, all usually divaricately branched or spurred at several nodes preceding the first peduncle, zigzag distally; stipules herbaceous or the lowest becoming papery, (1.5) 2.5-8 (9) mm. long, broadly ovate-acuminate, ovate, or lance-acuminate, the lowest (sometimes all) amplexicaul-decurrent around half to nearly the whole stem’s circumference, free (exceptionally very obscurely united), the upper ones narrower, usually deflexed; leaves 3-8 cm. long, very shortly petioled, divaricate or ascending, with (7) 9-17 obovate or elliptic, acute, obtuse and mucronulate, or rarely retuse, mostly flat leaflets (3) 5-19 mm. long; peduncles erect, 1.5-5.5 cm. long, nearly always shorter than the leaf; racemes rather densely 10-25-flowered, the axis slightly elongating, (1) 2-5 cm. long in fruit; bracts herbaceous, lanceolate or linear-lanceolate, (2.5) 4-12 mm. long; pedicels ascending, straight, at anthesis 0.5—1.2 mm., in fruit a trifle or not thickened, 0.9—2.3 mm. long; bracteoles 0-2, sometimes conspicuous and up to 4 mm. long; calyx 9.5—13 mm. long, very thinly to quite densely hirsute or hirsutulous with white or white and some black hairs, the subsymmetric or strongly oblique disc 1-1.5 (1.7) mm. deep, the membranous, pallid or pinkish tube 7—8.6 mm. long, 3—4.7 mm. in diameter, the subulate or linear-lanceolate teeth 2.5—5.5 mm. long, the whole becoming papery-scarious, ruptured, marcescent; banner gently recurved through ± 45—50°, broadly oblanceolate to ovate-cuneate, 14-20.3 mm. long, (6.2) 7—10 mm. wide; wings (0.3) 1—4 mm. longer than the banner, 17.5—23.7 mm. long, the claws 7-9.4 mm., the oblong-oblanceolate, nearly straight blades 10.5-16 mm. long, shallowly notched or erose on the lower margin just below the more or less obliquely distended apex, 3—5 mm. wide; keel shorter than the banner, 12-15.3 mm. long, the claws 7-8.9 mm., the lunately half-elliptic or -obovate blades 5.3-7.2 mm. long, 2.7-3.8 mm. wide, incurved through 50-95° to the obtusely deltoid or triangular apex; anthers 0.6-0.8 mm. long; pod ascending or erect, sessile on a minute boss and readily disjointing when ripe, linear- oblong or -lanceolate in profile, nearly straight to lunately incurved through about ¼ circle, (2) 2.5-4 cm. long, (4) 5-7 (8) mm. in diameter, obtuse at base, broadly cuneate to narrowly triangular-acuminate and minutely cuspidate at apex, compressed-triquetrous with sharply carinate ventral and narrow but obtuse lateral angles, the almost flat lateral faces much broader than the narrowly or (at maturity) openly and deeply sulcate dorsal face, the thin, pale green, glabrous valves becoming papery, stramineous, somewhat lustrous, finely cross-reticulate, inflexed as a complete or nearly complete septum 1.2-2.5 mm. wide; seeds buff or olivaceous, often purple-speckled, lustrous but minutely pitted, 1.8-2.9 mm. long.—Collections: 40 (ii); representative: J. W. Thompson 11,442 (CAS, NY, RM, RSA, WS); Cronquist 6498 (ID, NY, TEX, WS); Ripley & Barneby 10,776 (CAS, RSA, WILLU).

Dunes and sandy barrens along the Columbia River and its immediate affluents, 250-1000 feet (reportedly up to 2350 feet in Gilliam County, Oregon), locally plentiful and rather common from Kittitas and Grant Counties, Washington, downstream to Gilliam County, Oregon, apparently most abundant between the mouths of the Yakima and Umatilla Rivers.—Map No. 153.—April to July.

Astragalus succumbens (lying down) Dougl. ex Hook., Fl. Bor.-Amer. 1: 151. 1831.—"On the barren grounds of the Columbia and near the Wallawallah River, North-West America. Douglas."—Holotypus, from "the junction of Wallahwallah River with the Columbia, 1826," K! isotypi, BM, GH (fragm.)! the spm. dated 1830 at G is perhaps also an isotypus!—Tragacantha succumbens (Dougl.) O. Kze., Rev. Gen. 948. 1891. Phaca succumbens (Dougl.) Piper in Contrib. U. S. Nat. Herb. 11 (Fl. Wash.): 370. 1906. Hamosa succumbens (Dougl.) Rydb. in Bull. Torr Club 54: 14. 1927.

The crouching milk-vetch, A. succumbens, is a plant of strong individuality and of great beauty when in flower. It is easily recognized by its low, rather coarse, distally zigzag stems, copious hirsute vesture, and long, ascending, sessile, compressed-triquetrous pods becoming straw-colored and glossy in the course of ripening. The flowers are remarkable for the exserted, apically dilated and (commonly) notched wings, which are either white or at least much paler than the roseate-purple banner. In relation to the pod’s size, the seeds are unexpectedly small.

The identity of A. dorycnioides, traditionally listed as a synonym of A. succumbens, is discussed in Appendix I.