Astragalus pattersonii A.Gray ex Brandegee
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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
"The only flowering specimens were collected by Mr. H. N. Patterson ... in the foothills of the Gore Mountains, Colorado ... "—Holotypus, collected by Patterson on July 28, 1876, on the Harris & Co. Ranch in the foothills of the Gore Mountains, Middle Par
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Description
Species Description - Similar in growth-habit to A. praelongus, usually robust, with several or many erect and ascending stems forming well-furnished clumps, the stems glabrous below the middle, often thinly strisulous distally, the thick-textured herbage green or sometimes pallid-elaucescent, the leaflets (at least some upper leaves) thinly strigulose beneath with fine, straight, appressed hairs up to 0.2-0.5 mm long, the inflorescence usually black-strigulose; stems 2-5 dm. long, usually tinged with red (drying reddish- or purplish-brown), rarely green, simple or shortly spurred at some lower or median axils, often flexuous or zigzag distally; stipules 3-8 mm. long, all firm, purplish, becoming papery and brownish, or the upper ones (occasionally all) pallid and membranous, all ± amplexicaul-decurrent the lowest around 3/4 to the whole stem's circumference, sometimes obscurely united, the upper ones triangular-lanceolate, semiamplexicaul; leaves 5-13 cm. long, shortly petioled or the uppermost subsessile, with (9) l5-25 (29) commonly oblong-elliptic leaflets 5-30 mm. long, those of the upper leaves varying from obtuse to Sharply acute, nearly always narrower than the retuse to obtuse sometimes mucronulate ones of the lower leaves; peduncles erect, usually stout, (3) 5 14 cm. long; racemes 10-25-flowered, rather dense at early anthesis, the flowers nodding and ± retrorsely imbricated, the axis soon elongating, 3—15 cm. long in fruit; bracts membranous, lanceolate or lance-acuminate, 2—8 mm. long; pedicels at anthesis 1-1.5 mm. long, in fruit ascending, straight, 1.7-4 (4.5) mm. long; bracteoles 2, commonly conspicuous; calyx (8.8) 10.5-14.2 mm. long, white or red- tinged, thinly white- or black-strigulose, the oblique disc 0.9-1.5 mm. deep, the membranous, deeply campanulate or cylindric, nearly always basally pouched tube (6) 6.5-8.8 mm. long, 3.5-4.8 mm. in diameter, the narrowly lance-acuminate or subulate-setaceous, spreading or loosely recurving teeth (2.3) 3-6.8 mm. long; petals white, the keel-tip faintly maculate; banner recurved through 50-90°, 14.6-21.5 mm. long, the long-cuneate claw expanded into an oval or ovate, truncate, mucronulate, erose-emarginate, or very shallowly retuse blade 6—10 mm. wide; wings 14.8-20 mm. long, the claws 7.2-9.1 mm., the oblong-oblanceolate or -lanceolate, rarely elhptic or narrowly ovate, obtuse or subacute blades 8.4— 12.2 mm. long, 2.7-4 mm. wide; keel 12.4-15 mm. long, the claws 7-9 mm., the lunately half-elliptic blades 5.7-7.5 mm. long, 2.5-3.5 (3.8) mm. wide; anthers 0.7-0.85 mm. long; pod strictly erect, sessile, oblong-ellipsoid, lance-ellipsoid, or narrowly ovoid, (1.7) 2-3.5 (3.8) cm. long, 6-10 mm. in diameter, rounded or cuneate at base, abruptly contracted distally into a rigid, cuspidate beak, straight or commonly a little incurved, nearly terete to strongly obcompressed at maturity, the thick, salient ventral suture either convexly or (in the lower 1/2-2.3) concavely arcuate (then depressed and lying in a double groove), the succulent, green or reddish-green, glabrous or rarely puberulent valves becoming stiffly leathery, brown or stramineous, rugulose-reticulate, inflexed as a sometimes obscure septum 0.3—1.4 mm. wide; ovules 22-38; seeds smooth, pale or greenish-brown, ± 3-3.5 mm. long.
Distribution and Ecology - Open banks, gullied hillsides, barren knolls, and over-grazed pastures, usually in stiff adobe or gumbo soils, (5400) 6000-8250 feet, rather frequent and locally plentiful in the oak-brush belt along the west slope of the Colorado Rocky Mountains, from the upper White and Grand Rivers south to the upper tributaries of the San Juan, west to the south slope of the Uintah Mountains in northern Uintah County, Utah; also disjunctly on red clay hills, ± 4900 feet, in the valley of Kanab Creek at the north edge of Coconino County, Arizona.—Map No. 73.—May to July, the dead fruits often persistent over winter.
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Discussion
The Patterson milk-vetch is closely related to A. praelongus and the two species have often been confounded. Even in the first instance Gray’s description of the pod was based partly on material of A. praelongus collected by Ward in Utah. The attention of botanists has been focused so intently on the fruit, to the exclusion of valuable characters in the flowers, that the apparent or claimed differences between the two have become increasingly nebulous. The pod of A. Pattersoni is quite variable in length, shape, and maximum diameter, sometimes in one colony of plants, and no single feature of the fruit’s form provides a satisfactory differential character. However, sharply defined discontinuities in ovule-number, in form of the calyx, in flower-color, and in shape of the keel-petals effectively separate A. Pattersoni from A. praelongus, all forms of which have essentially the same flower but extremely variable pods. While A. praelongus is a plant of desert and semidesert environments, climbing to 7100 feet only on the arid crest of the Continental Divide in northwestern New Mexico, A. Pattersoni is characteristic of middle elevations in the Rocky Mountains, in the relatively well-watered oak belt between 6000 and 8000 feet. The disjunct occurrence of an extensive and vigorous population of the Patterson milk-vetch on the badlands of Kanab Creek in Arizona (near Fredonia, Ripley & Barneby 4361, CAS, RSA), over two hundred miles west of the main range, can be explained rationally only by assuming the species to be introduced in this locality. Typical A. praelongus is found in quantity on the same ridge, apparently in identical environment, although the two species are not directly associated or intermingled.
The Patterson milk-vetch is ordinarily recognized in the field by its shining red (rarely green) stems which form a handsome contrast with the green or glaucescent foliage and snow- white flowers. Calyx and petals are usually of the same clear white, but the former is sometimes tinged with red and the keel-tip is faintly lavender-tipped. The calyx-teeth are commonly crowded toward the dorsal side of the tube and more or less stellately recurved or distally hooked. The Patterson milk-vetch is as ill-scented and as poisonous as the commoner A. praelongus, but is found in a region where palatable forage is more easily available to stock. The plants are often trampled by cattle, but are seldom browsed.
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Objects
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Distribution
Utah United States of America North America| Arizona United States of America North America|