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Astragalus cremnophylax
Astragalus cremnophylax Barneby
Cliff Milkvetch, Sentry Milkvetch
Fabaceae (Pea family)
Synonym(s):
USDA Symbol: ASCR3
USDA Native Status: L48 (N)
"Diminutive, matted or somewhat mounded, essentially acaulescent but suffruticulose, with a gnarled, closely ramifying caudex, the ultimate divisions becoming columnar from a sand-impacted thatch of fibrous, decaying leaf-bases, the herbage silvery-strigulose with truly appressed, straight hairs up to 0.3—0.35 mm. long, mature plants forming low-convex cushions up to 2 dm. in diameter; stems of the year not over 5 mm. long, concealed by imbricated stipules." (bibref: 1814).
"The sentry milk-vetch is one of our rarest species. It was first discovered in 1903 by Marcus Jones, who mistook it for A. humillimus and reported it (1923, p. 82, Pl. 6, fig. 19) as "apparently common at the Grand Canyon ... on sandy ledges." Search in recent years has revealed, however, only a single group of perhaps a hundred plants confined to a strip of rock pavement not over fifty yards in length. They are scattered over the area, some in full sun and rooting in scarcely visible cracks of the limestone, others standing back among the piñons and rooting into sand-filled hollows of the rock. It is to be sought elsewhere in the region, perhaps on some of the buttes which stand out in isolation from the canyon wall." (bibref: 1814).
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Plant Characteristics
Duration: PerennialHabit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Mature plants forming low-convex cushions up to 2 dm. in diameter; stems of the year not over 5 mm. long." (bibref: 1814).
Leaf: "Stipules deltoid- ovate, subobtuse, 1-3 mm. long, fully amplexicaul but free, the nearly glabrous or distally puberulent blades squarrose, becoming papery and brownish in age; leaves 3-9 (12) mm. long, with (3) 5-9 crowded, sometimes subpalmate, elliptic, obovate, or suborbicular, obtuse, thick-textured, folded leaflets 1-2.5 mm. long." (bibref: 1814).
Flower: "Peduncles subfiliform, up to 5 mm. long, reclinate in fruit; racemes 1-3 (commonly 2)-flowered, the flowers loosely ascending, the fruiting axis not over 2 mm. long; bracts membranous, ovate, 0.6-1 mm. long; pedicels ascending, nearly straight, at anthesis about 0.7 mm., in fruit about 1 mm. long; bracteoles 0; calyx 2.7-3.5 mm. long, strigulose with mixed black and white hairs, the subsymmetric disc 0.3-0.4 mm. deep, the campanulate tube 1.7-2.3 mm. long, 1.5-1.7 mm. in diameter, the subulate, obtuse teeth 0.8-1.4 mm. long; petals pale pinkish-lilac, the wings white-tipped, the banner purple-veined, the keel-tip maculate; banner recurved through 45 degrees, broadly ovate- or suborbicular-cuneate, shallowly notched, 5.3-6.1 mm. long, 4.3-4.6 mm. wide; wings as long or a trifle shorter, the claws 1.9-2.1 mm., the ovate-elliptic, obtuse blades 3.5-4.4 mm. long, 1.6-2 mm. wide, both incurved but the left one more strongly so and its inner margin infolded; keel 3.7-4.3 mm. long, the claws 1.7-2 mm., the half-obovate or nearly half- orbicular blades 2-2.8 mm. long, 1.3-1.7 mm. wide, abruptly incurved through 100-120 degrees to the bluntly deltoid, minutely porrect apex; anthers 0.3-0.45 mm. long." (bibref: 1814).
Fruit: "Pod ascending (mostly humistrate), obliquely ovoid, 3-4 (4.5) mm. long, about 2.5 mm. in diameter, rounded at base, flattened or slightly depressed dorsally, carinate ventrally by the prominent, thick, convexly arched suture, contracted distally into a minute, declined, deltoid beak, the thinly fleshy, pale green or purple- dotted, densely strigulose valves becoming papery and stramineous, obscurely reticulate; ovules 4-6; seeds amber-yellow or pale orange, smooth or nearly so, dull, 1.4-1.8 mm. long." (bibref: 1814).
Bloom Information
Bloom Color: White , Pink , Purple , VioletBloom Time: May , Jun
Bloom Notes: "Petals pale pinkish-lilac, the wings white-tipped, the banner purple-veined, the keel-tip maculate." (bibref: 1814).
Distribution
USA: AZNative Distribution: "Known only from one colony of plants on the South Rim of the Grand Canyon of the Colorado River, near El Tovar, Coconino County, Arizona." (bibref: 1814).
Native Habitat: "Crevices of limestone pavement in the piñon belt, about 7050 feet." (bibref: 1814).
Bibliography
Bibref 1814 - Atlas of North American Astragalus Volume 2 (1964) Barneby, Rupert C.Search More Titles in Bibliography
Additional resources
USDA: Find Astragalus cremnophylax in USDA PlantsFNA: Find Astragalus cremnophylax in the Flora of North America (if available)
Google: Search Google for Astragalus cremnophylax
Metadata
Record Modified: 2020-12-07Research By: Joseph A. Marcus