Astragalus tweedyi M.L.Canby
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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
“Collected by Mr. Howell ‘in prairies, Eastern Oregon,’ and distributed by him as Astragalus collinus Dougl.; and by Mr. Tweedy (no. 613) and Mr. Brandegee (no. 731) on ‘hills along the Columbia River, Yakima County, Washington territory’."—Lectotypus, la
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Synonyms
Phaca tweedyi (Canby) Piper, Homalobus tweedyi (Canby) Rydb.
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Description
Species Description - Robust perennial, loosely strigulose or villosulous with fine, incurved or sinuous hairs up to 0.35-0.55 mm. long, the herbage greenish or in youth cinereous, the leaflets pubescent on both sides, but often more thinly so and deeper green above; stems few, stout or occasionally slender and wiry, stiffly erect or ascending, (2.5) 3.5-8 dm. long, subterranean for a space of 1.5-5 cm., naked and usually simple through the lowest emersed internodes, thereafter leafy, paniculately branched and bearing several spurs in the median axils, the whole composed of ± 10-17 internodes; stipules (1) 2-7 mm. long, the lowest shortly adnate to the suppressed petiole, ovate or broader than long, early becoming papery and irregularly deciduous, decurrent around 1/3 to nearly the whole stem’s circumference, the median and upper ones herbaceous, deltoid, triangular, or drawn out into a lanceolate, often deflexed blade; leaves 3-10 (13) cm. long, subsessile or the lowest ones shortly petioled, with (7) 11-23 narrowly oblong- oblanceolate to linear-oblong, retuse, truncate, rarely obtuse, flat or loosely folded leaflets 5-18 (25) mm. long; peduncles erect, (5) 7-15 cm. long, usually well surpassing the leaf; racemes 12-35 (40)-flowered, rather compact at early anthesis, the axis elongating, 2.5-10 cm. long in fruit; bracts narrowly ovate to lanceolate, 1.5-6 mm. long; pedicels ascending, straight, at anthesis 0.8-2 mm., in fruit somewhat thickened, 1-3 mm. long; bracteoles 0; calyx 8-10.5 mm. long, villosulous with white and sometimes a few black hairs, the strongly oblique disc 0.8-1.6 mm. deep, the tube 7.5-9 mm. long, (3.3) 3.8-5 mm. in diameter, gibbous-convex behind the pedicel, the broadly subulate teeth 1-2.1 mm. long, the ventral pair commonly deltoid and shorter than the rest, the whole becoming papery, marcescent unruptured; petals ochroleucous, immaculate; banner broadly oblanceolate, 15-18.6 mm. long, the blade recurved through ± 45°, sometimes further in age, (5) 6.8-9 mm. wide; wings (14.2) 15-18 mm. long, the claws 7.5-9.6 mm., the oblong-elliptic or -oblanceolate, obtuse, nearly straight blades (7.4) 8-9.5 mm. long, (2.3) 2.8-3.6 mm. wide; keel 11.5-14.3 mm. long, the claws 7.2-8.9 mm., the half-obovate blades 4.5—6 mm. long, 2.7—3.4 mm. wide, abruptly incurved through 85-95° to the bluntly deltoid apex; anthers 0.5-0.7 mm long; pod stipitate, the stiff but slender, ascending stipe 6—10 mm. long, incurved distally to bring the body to perpendicular at a distance from the raceme-axis, the body oblong-ellipsoid, cuneate or shortly acuminate at base, abruptly cuspidate-beaked, (1) 1.2-1.5 cm. long, (3) 3.4-4 (5.4) mm. in diameter, a little compressed laterally, with strongly convex faces, bicarinate by the elevated sutures, the green, glabrous, lustrously fleshy valves becoming stramineous, stiffly leathery, transversely rugulose-reticulate and often wrinkled lengthwise, not inflexed; dehiscence apical, the beak gaping to release the seeds; seeds (little known) brown, apparently smooth, and ± 2—2.5 mm. long.
Distribution and Ecology - Dry hillsides, grassy banks, and stony meadows or hilltops, in light dry basaltic soils, sometimes among sagebrush, 250-2350 ("3000") feet, locally plentiful in the lower Deschutes and Columbia Valleys in Wasco, Sherman, and Gilliam Counties, Oregon, and adjacent Klickitat County, Washington; one old record from Columbia River in Yakima County, Washington. — Map. No. 29. — Late May to July, the fruit long persisting.
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Discussion
The Tweedy milk-vetch is a tall, graceful astragalus, with comparatively few, erect, and often paniculately branching stems and handsome, rather dense racemes of ascending creamy- white flowers. It is technically remarkable for its tumid, pallid, basally pouched calyx and incurved-ascending, stipitate, unilocular pod which remains securely attached to the raceme-axis until after dehiscence, indeed long after the seeds themselves are shed. The fruits are similar in structure to those of A. collinus, but less strongly compressed, of somewhat thicker texture, and they tend, like those of several Reventi-arrecti, to become wrinkled lengthwise as well as reticulate when fully ripe or dried.
All modern records of A. Tweedyi are concentrated into a small area along the Columbia and lower Deschutes Rivers, extending along the Columbia from the mouth of Willow Creek to that of the John Day, thence south to Tygh Valley and Maupin, where the species is locally abundant. The type-locality, supposedly on the Columbia in Yakima County, has not been confirmed but has been mapped arbitrarily in the northeast corner of the county.
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Objects
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Distribution
Oregon United States of America North America| Washington United States of America North America|