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Astragalus cerussatus
Astragalus cerussatus Sheldon
Powdered Milkvetch, Powdery Milkvetch
Fabaceae (Pea family)
Synonym(s):
USDA Symbol: ASCE2
USDA Native Status: L48 (N)
"Low, slender, diffuse, with a short-lived perennial taproot but flowering the first season and then appearing annual, thinly villosulous throughout with fine spreading or ascending, nearly straight or crisply sinuous hairs up to 0.5-0.8 mm. long, the stems and herbage green or in youth subcinereous, the leaflets sometimes glabrescent above; stems several, ascending or decumbent with ascending tips, 0.3-2.5 dm. long, in older plants becoming somewhat indurated at base but scarcely caudiciform, branched or bearing short spurs at most of the axils, together forming densely leafy tufts or loose, low clumps." (bibref: 1814).
"The powdered milk-vetch, A. cerussatus, is a pretty but inconspicuous astragalus, with diffuse stems, tiny, milky-lilac flowers, and swollen fruits of notably delicate texture. It is found most commonly on gravel bars or sandbars along the flood plain of the Arkansas River or in the beds of torrents lateral to the main stream, and in these situations the older plants must be subject to flooding in the spring thaws. The average plant of A. cerussatus is of rapid growth and short duration, coming into flower two or three months after germination of the seed and fruiting soon after. Some colonies seem to be composed entirely of annuals. Elsewhere, however, individuals may be found with flowering stems arising from a base already indurated and caudiciform in early spring, and these are doubtless in their second or third season." (bibref: 1814).
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Plant Characteristics
Duration: Annual , PerennialHabit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Stems several, ascending or decumbent with ascending tips, 0.3-2.5 dm. long." (bibref: 1814).
Leaf: "Stipules thinly herbaceous, deltoid or lanceolate, 2-4 mm. long, semiamplexicaul, free; leaves 2.5-8 cm. long, shortly petioled, with subfiliform rachis and 13-21 narrowly oblanceolate to oblong-oblanceolate, retuse or sometimes obtuse, thin, flat leaflets 4-13 (18) mm. long." (bibref: 1814).
Flower: "Peduncles very slender, incurved-ascending, 2-4.5 cm. long, or some arising late in the season from axillary spurs only 1 cm. long or even less; racemes loosely (1) 3-7-flowered, the flowers at first ascending, declined in age, the axis 0.5-3.5 cm. long in fruit; bracts submembranous, ovate- or lance-acuminate, 1.5-2.5 mm. long; pedicels slender, at anthesis 1-1.2 mm., in fruit arcuate and 1.8-2.5 mm. long; bracteoles 0-2, minute when present; calyx 3.4-4.2 mm. long, villosulous like the herbage with white hairs, the disc about 0.5 mm. deep, the campanulate or obconic-campanulate tube 1.7-2 mm. long, about 1.6 mm. in diameter, the narrowly lance-subulate teeth 1.4-2.5 mm. long, the whole becoming papery, ruptured, marcescent; petals pale lilac, or whitish with lilac tips and pale purple veins in the banner; banner recurved through nearly 90 degrees, ovate-cuneate, 5.2-6 mm. long, 3.2-4.2 mm. wide; wings 4.7-5.6 mm. long, the claws 1.8-2.3 mm., the lunately lance-oblong, obtuse blades 3.4-3.9 mm. long, 1.1-1.7 mm. wide; keel 3.6-4.3 mm. long, the claws 1.7-2.2 mm., the broadly half-obovate blades 2-2.5 mm. long, 2-2.5 mm. wide, abruptly incurved through 120 degrees to the obliquely deltoid, obscurely porrect apex; anthers 0.3-0.4 mm. long." (bibref: 1814).
Fruit: "Pod spreading or declined, sessile, readily deciduous, obliquely ovoid or ovoid-ellipsoid, bladdery- inflated, 1-2.2 cm. long, 5-14 mm. in diameter, rounded or broadly obconic at base, contracted distally into a shortly deltoid, laterally flattened beak, otherwise a trifle obcompressed, shallowly sulcate ventrally, the filiform dorsal suture more strongly convex than the ventral one, the thin, greenish or sometimes purplish valves thinly strigose-villosulous with incumbent or curly hairs 0.3-0.5 mm. long, becoming papery-membranous, stramineous, delicately reticulate, inflexed as a very narrow partial septum 0.1-0.4 mm. wide, the funicular flange about 0.5 mm. wide; dehiscence apical, after falling; ovules 18-22; seeds olivaceous-brown, sometimes purple-speckled, smooth but dull, 1.9-2.5 mm. long." (bibref: 1814).
Bloom Information
Bloom Color: White , Purple , VioletBloom Time: Apr , May , Jun , Jul , Aug
Bloom Notes: "Petals pale lilac, or whitish with lilac tips and pale purple veins in the banner." (bibref: 1814).
Distribution
USA: CONative Distribution: "Rather local but forming colonies, known only from southern Colorado: along the Arkansas River from Canon City upstream to Poncha Springs and Salida, Fremont and Chaffee Counties; on the upper Rio Grande and Conejos River in Costilla and Conejos Counties; and on the La Plata River near Durango, La Plata County; reported (Rydberg, 1929, p. 352) from northern New Mexico." (bibref: 1814).
Native Habitat: "Dry sandy banks and hillsides, and sandbars and shingle bars along rivers and torrents, 5400-8300 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 cerussatus in USDA PlantsFNA: Find Astragalus cerussatus in the Flora of North America (if available)
Google: Search Google for Astragalus cerussatus
Metadata
Record Modified: 2020-12-07Research By: Joseph A. Marcus