Astragalus crotalariae (Benth.) 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(1): 1-596.
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Family
Fabaceae
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Scientific Name
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Type
"Juxta Monterey legit Coulter."—Holotypus, Coulter 436, labeled "Monterey, California," K (herb. Benth.)!
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Synonyms
Phaca crotalariae Benth., Tragacantha crotalariae (Benth.) Kuntze, Astragalus limatus E.Sheld., Astragalus preussii var. limatus (E.Sheld.) Jeps.
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Description
Species Description - Coarse, leafy, ill-scented but handsome perennial, of rapid growth, often flowering the first season, strigulose, strigulose-pilosulous, or exceptionally pilose with fine, straight, appressed and often (especially the stems upward) some narrowly ascending hairs up to 0.5-0.9 (1.2) mm. long, the herbage green, yellowish- green, or the growing tips cinereous, rarely cinereous throughout, the leaflets commonly glabrous but sometimes thinly pubescent above; stems usually several or numerous, erect and ascending in bushy clumps, or in seedling plants erect and solitary, 1.5-5 (6) dm. long, angular-striate and hollow when vigorous, simple or commonly spurred at 1 or several nodes preceding the first peduncle, floriferous upward from near or above the middle; stipules thinly herbaceous becoming papery, pallid, fragile in age, broadly deltoid or ovate, commonly broader than long or broader than the stem, 4-12 mm. long, several-nerved, decurrent around half to nearly the whole stem’s circumference, the obtuse or shortly acuminate blades recurved or reflexed; leaves 5-14 (16.5) cm. long, the lower ones petioled, the upper subsessile, with stout, tapering rachis and 9-17 (19, or in some seedlings only 3-9) obovate-cuneate, broadly oblong-obovate or -elliptic, or (in some leaves) suborbicular-obcordate, retuse or emarginate, flat, thick-textured leaflets (5) 7-30 (35) mm. long; peduncles stout, erect, (5) 7-17 cm. long, a little longer or shorter than the leaf; racemes loosely, or at first rather closely, 10-25- flowered, the flowers ascending at a wide angle, the axis somewhat elongating, (2) 3-10 cm. long in fruit; bracts submembranous, broadly ovate, ovate-acuminate, or lanceolate, 1.5-4 mm. long; pedicels ascending, straight or a trifle arched outward, at anthesis 1.2-2.2 mm., in fruit thickened, 2.8-4.5 mm. long; bracteoles 2, rarely vestigial or 0; calyx (7.6) 8-12.3 mm. long, strigulose or pilosulous with black, fuscous, or mixed black and white hairs, the oblique disc 1.2—2 mm. deep, the submembranous, deeply campanulate or subcylindric, red- or purple-tinged tube (6 3) 6 7-9.7 mm. long, (3.6) 3.9-6.5 mm. in diameter, the subulate or triangular-subulate teeth (1.3) 1.8-2.7 mm. long, the dorsal one often the shortest, the ventral pair sometimes broadly deltoid, the whole becoming papery, fragile, ruptured but usually marcescent, rarely tardily circumscissile; petals rosy- or magenta-purple, drying violet, sometimes all white; banner recurved trough ± 40°, broadly to narrowly rhombic-oblanceolate, shallowly notched 21-27 (28 mm. long, 8.2-13 (14) mm. wide; wings 19.5-24 (25) mm. long, the claws (8.8) 9.4-11.3 mm., the linear-oblong or -elliptic, obtuse, nearly straight blades (11.1) 12.4-15 mm long, 2.9-4.8 mm. wide; keel 17.4-21 mm. long, the claws (8.8) 9.2-11.3 mm., the half obovate or lunately half-elliptic blades 8.9-11 mm. long, (3) 3.2-4.8 mm. wide, incurved through 50-90° to the rounded apex; anthers (0.7) 0.8-1 mm. long; pod ascending or somewhat spreading, subsessile, the broadly ellipsoid, oblong- or ovoid-ellipsoid body (2) 2.3-3 cm. long, 1-1.4 cm. in diameter, inflated bud hardly bladdery, cuneately or truncately contracted at base into a thick, turbinate, stipelike neck 1-1.5 mm. long, narrowed distally into a very short, erect or slightly incurved, triangular-acuminate beak tipped by the persistent style-base, the whole slightly compressed laterally, bicarinate by the slender sutures (these subequally convex as seen in profile or the ventral one less so), the lateral faces broadly and plumply rounded, the green, thinly fleshy, sparsely to quite densely strigulose valves becoming stramineous, papery, finely but prominently cross-reticulate, sparsely filamentous within, not inflexed, or inflexed as a vestigial septum up to 0.4 mm. wide; dehiscence apical and downward through the ventral suture; ovules (24) 28-38; seeds brown, sometimes speckled with purple, nearly smooth or sparsely punctuate, dull, 3-4.3 mm. long.
Distribution and Ecology - Plains, valley floors, washes, and outwash fans in the foothills of desert mountains or on open desert, in sandy or gravelly soils, sometimes on dunes, rarely along irrigation ditches, with Larrea, -220-800 feet, locally abundant in the Colorado Desert, southeastern California, from the head of the Salton Sea south to Carrizo Valley, southeast through Imperial Valley to the Yuma Desert in extreme southwestern Arizona, and south just into Baja California.—Map No. 72.— January to April.
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Discussion
The rattle-box milk-vetch, A. Crotalariae, is by far the handsomest astragalus found on the floor and surrounding outwash fans and sand plains of the Salton Sink, readily known by its long flowers and stiffly papery, swollen fruits. The plants are potentially perennial and, granted the right conditions for growth, form vigorous clumps of stems arising from a thick, woody taproot; but they mature rapidly and often flower within three or four months after germination of the seed. Depending on rainfall and on timing of the rains, the populations vary greatly in numbers from year to year. After several years of drought only a few aged and ailing veterans may be found along a wash where a few seasons earlier, following one or especially two successive wet winters, the plants could be numbered in the thousands, thronging the interspaces between the larreas for mile on mile. An albino form, with pure white petals but either purple or pallid calyx, is rather frequent, and the mutation is probably inherited, for sometimes whole colonies of white-flowered plants are found among the usual purples.
The misleading data furnished by Coulter for this and other desert species, encountered on his journey from Monterey to the mouth of the Gila River in 1832, has been the source of lasting confusion. The epithet Crotalariae was applied by Gray to A. Nuttallii, the only astragalus with bladdery pod found in the immediate vicinity of Monterey Bay; and later by Torrey to A. oocarpus, a species with rather similar inflated fruits but much smaller, ochroleucous flowers. The material in Bentham’s herbarium at Kew was examined by I. M. Johnston (fide Jones, Contrib. West. Bot. 15: 69, the name misspelled "crotalarioides") and then first identified positively with A. limatus Sheld.; the determination is confirmed by Bentham’s excellent description, and by re-examination of Bentham’s specimen.
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Objects
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Distribution
Arizona United States of America North America| California United States of America North America| Baja California Mexico North America|