Astragalus oxyphysus

Tall, robust perennial, with taproot and stems at length ± indurated at base, villosulous nearly throughout with fine, ascending, incurved, wavy, or curly hairs up to 0.6-0.95 mm. long often mixed with a few longer, straighter ones up to 1-1.6 mm. long, the stems and those leaves developing before and with the flowers greenish-cinereous, the leaflets sometimes glabrescent above, those leaves developing after the flowers and those of basal innovations produced late in the season more densely pubescent, commonly white-tomentose; stems several or numerous, erect and ascending in bushy clumps, stout, striate, fistular at base, (1.5) 3-8 dm. long, bearing a slender branch or spur at 1-several nodes preceding the first of some 3-5 (6) peduncles, rarely a spur and peduncle together in the same axil; stipules submembranous becoming papery-scarious and fragile, the lowest often early deciduous, deltoid, triangular- or lance-acuminate, (3) 4-12 mm. long, the lowermost ones amplexicaul and connate (at least in vernation) through ± half their length into a bidentate sheath (but this often ruptured by the expanding stem), the median and upper ones embracing ± half the stem, all thinly, or the upper ones densely pubescent dorsally; leaves (4.5) 7-17 cm. long, all shortly petioled or the upper ones subsessile, with (11) 17-29 (31) broadly to narrowly lance- or oblong-elliptic, or oblong-obovate, obtuse, subacute, truncate and mucronulate, or (in some lower leaves) retuse, flat leaflets (4) 7-32 mm. long; peduncles stout, erect, (4) 7-17 cm. long, mostly as long or longer than the leaf; racemes 20-60 (65)-flowered, loose or early becoming so, the flowers at first ascending, loosely declined or nodding in age, the axis elongating, (4.5) 6-22 (25) cm. long in fruit; bracts membranous, lanceolate or lance-ovate, 2-3.5 mm. long; pedicels ascending, straight or arched outward, at anthesis 1.2-2 mm., in fruit thickened, persistent, 2-4 mm. long; bracteoles 0-2; calyx 8.7-10.3 mm. long, villosulous with mixed white and fuscous or black hairs, the slightly or strongly oblique disc 1.3-2 mm. deep, the cylindric or deeply campanulate tube 5.9-8.4 mm. long, 2.8-3.8 mm. in diameter, the subulate or triangular-subulate teeth 1.6-3.7 mm. long, the dorsal one often shorter, rarely longer than the rest, the orifice oblique, the whole becoming papery, marcescent unruptured; petals pale cream-color or almost white, immaculate; banner gently recurved through ± 50° (or further in withering), oblanceolate, rhombic- or elliptic-oblanceolate, 15.3-18 (19) mm. long, 5—8.2 mm. wide, shallowly notched or subentire at apex; wings 14.6—17.1 mm. long, the claws 7.4—8.9 mm., the narrowly oblong-oblanceolate, obliquely emarginate or (when narrow) entire and obtuse, slightly incurved blades 8-9.8 mm. long, 2-3.2 mm. wide; keel 13.1-14.7 mm. long, the claws 7.6-9.1 mm., the lunately half-elliptic blades 5.9-6.4 mm. long, 2.4—3 mm. wide, gently incurved through 70-90° to the bluntly triangular apex; anthers 0.55-0.8 mm. long; pod spreading or loosely pendulous, sessile but elevated on and readily disjointing from a slender, densely villosulous, outwardly arched, stipelike gynophore 3-11 mm. long, the body obliquely elliptic, half-elliptic, or rhombic-elliptic in profile, (2.1) 2.5—4.5 cm. long, (6) 8—15.5 mm. in diameter, downwardly acuminate from above the middle, more shortly acuminate or triangular distally, bladdery- inflated but also laterally compressed, bicarinate by the filiform, salient sutures, the thin, pale green, sparsely strigulose (or in age glabrate) valves becoming papery, stramineous, lustrous, semitransparent, delicately cross-reticulate, not inflexed, the funicular flange obscure, not over 0.3 mm. wide; dehiscence apical, after falling; ovules 11—18; seeds brown, sometimes purple-speckled, smooth or sparsely pitted, dull, 3-3.9 mm. long.—Collections: 47 (vii); representative: L. S. Rose 49,140 (CAS, SMU, WIS, approximate topotypi); Eastwood 6907 (CAS, NY); Ferris & Bacigalupi 10,354 (NY, TEX, WS); C. B. Wolf 4577 (CAS, POM, TEX, WS); Eastwood & Howell 4080 (CAS, NY); Barneby 11,368 (CAS, RSA).

Rolling plains, grassy hillsides and canyon banks, mostly in arid grassland, 250-2200 feet, extending rarely up into the digger pine belt at 3200 feet, common and sometimes forming extensive and conspicuous colonies, inner South Coast Ranges and adjacent Great Valley of California, from the Mt. Hamilton Range, Stanislaus County, south to the upper Cuyama Valley and the foothills of the Tehachapi Mountains and extreme southern Sierra Nevada in Santa Barbara and Kern Counties; one station on the east slope of the Santa Lucia Mountains in northern San Luis Obispo County.—Map No. 111.—March to June.

Astragalus oxyphysus (with pointed bladders, of the fruit) Gray in Proc. Amer. Acad. 6: 218. 1864.—"California, Arroyo del Puerto, in the Mt. Diablo range, on dry hills, June 11, in flower and fruit, Dr. Brewer."—Holotypus, Brewer 1259, GH! isotypus, US!—Tragacantha oxyphysa (Gray) O. Kze., Rev. Gen. 947. 1891. Phaca oxyphysa (Gray) A. Hell., Muhlenbergia 2: 86. 1905.

The Stanislaus milk-vetch, A. oxyphysus, is one of the handsomest astragali, the flourishing adult plant forming noble clumps of stout, ascending stems. These are clothed in softly hairy leaves and from above the middle send forth three to six long racemes of nodding, ivory-white flowers succeeded by large, pendulous, papery fruits of lustrous, semitransparent texture. The outline of the pod, as seen in profile, varies from half-elliptic when the ventral suture is nearly straight to rhombic-elliptic when both sutures are bowed. The pod is usually broadest above the middle and acuminate downward, but sometimes acuminate toward both ends from near the middle. Jepson (1936, p. 349) has drawn attention to the white spot formed by the densely pubescent foliage developing above the flowering nodes, a feature not obvious until late in the season. The same silvery tops are found in the partly sympatric A. asymmetricus, and in one species of the desert interior, A. (Preussiani) sabulosus. The leaves of basal shoots produced toward the end of the active cycle of growth, early in June or thereabouts at low elevations in the San Joaquin Valley, are likewise more densely hairy than the more rapidly expanded vernal foliage.

No difficulty should be experienced in recognizing the Stanislaus milk-vetch once its unique characters are understood; but it does resemble one other astragalus of the region, A. asymmetricus, in stature and flower-size and the two species have often been confused. They may be distinguished by the following contrasts:

1. Pubescence of the leaves and calyx villosulous; pod elevated on a villosulous gynophore 3-11 mm. long, the body laterally compressed, carinate by the salient sutures, cuneately or acuminately narrowed downward into the joint with the gynophore; ovules mostly 12-18 — A. oxyphysus

1. Pubescence of the leaves and calyx silky-strigulose; pod elevated on a genuine stipe 1.4—4 cm. long, the body obliquely, balloon-shaped, not or only a trifle compressed laterally (the"sutures not salient), cuneately to subtruncately contracted at base into the stipe; ovules mostly 18-30 — A. asymmetricus

The Stanislaus milk-vetch has been of ill repute as a stock poison since the early days of settlement in California. According to Ernest Twisselmann, who has very kindly provided me with detailed information about the locoweeds of the Great Valley and South Coast Ranges, A. oxyphysus, sometimes called the diablo loco, is acknowledged toxic to cattle, sheep, and horses. The plants are rapidly fatal to sheep. Cattle suffer severely, but do not become addicted and ordinarily avoid browsing the astragalus if other forage is available. Horses are affected less by A. oxyphysus than by A. asymmetricus, although once they acquire a taste for the weed, the disease follows the same course, leading to complete neurological collapse. Twisselmann points out that A. oxyphysus grows in a drier belt than A. asymmetricus and is green for a shorter time; on this score it is the less dangerous of the two. Much effort has been expended on control of A. oxyphysus, but it is still locally abundant and in no danger of extinction. Chemical sprays have been used against it, but even though these are effective temporarily, unremitting vigilance is required, the species soon becoming abundant again on neglected land.