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Astragalus aridus

Astragalus aridus A. Gray

Annual Desert Milkvetch, Parched Milkvetch

Fabaceae (Pea family)

Synonym(s):

USDA Symbol: ASAR5

USDA Native Status: L48 (N)

"Annual, of 2-4 months duration, variable in stature, either low and very slender or becoming robust and coarse in favorable seasons, with a slender or subfiliform taproot, densely strigulose-pilosulose (-pilose) with fine, shorter, appressed and straight together with some or many longer, straight or subsinuous and narrowly ascending hairs up to 0.6-1.1 mm. long, the stems and herbage silky- or almost satiny-canescent, the leaflets equally pubescent on both sides; stems solitary and erect in small plants, more commonly 3 from the root-crown and these often branched or spurred at each node preceding the first peduncle, decumbent with ascending tips or eventually diffuse and trailing, (2.5) 5-30 cm. long." (bibref: 1814).

"The parched milk-vetch, A. aridus, is a most distinct species, recognized at a glance by its obviously annual root, silvery or satiny pubescence extending up to the small, ascending, turgid but scarcely bladdery fruits, and its tiny, flesh-pink flowers which turn straw-color in drying." (bibref: 1814).

 

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Plant Characteristics

Duration: Annual
Habit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Stems decumbent with ascending tips or eventually diffuse and trailing, (2.5) 5-30 cm. long." (bibref: 1814).
Leaf: "Stipules thinly herbaceous becoming papery, commonly purplish, ovate, triangular, or triangular-acuminate, 1.5-5 (6.5) mm. long, more or less semiamplexicaul- decurrent; leaves (2) 3-9 cm. long, petioled but the uppermost shortly so, with (7) 9-17 oblanceolate, oblong-oblanceolate, or elliptic, obtuse, truncate, or emarginate, flat or loosely folded leaflets 4-16 mm. long." (bibref: 1814).
Flower: "Peduncles incurved- ascending, 2-5.5 cm. long, shorter than the leaf; racemes loosely (3) 4-9-flowered, the flowers ascending, the axis elongating, 1.5-5.5 cm. long in fruit; bracts subherbaceous, ovate or lanceolate, 0.8-2.2 mm. long; pedicels ascending, straight or a trifle arched outward in age, at anthesis 0.2-0.5 mm., in fruit thickened, 0.5-1 mm. long, persistent; bracteoles 0; calyx 3.3-4.3 mm. long, densely silvery-pilose with white and rarely a few black hairs, the subsymmetric disc 0.6-0.9 mm. deep, the turbinate-campanulate tube 2.1-2.7 mm. long, 1.5-2.3 mm. in diameter, the broadly subulate, herbaceous teeth 1-1.6 mm. long, the whole becoming papery, ruptured, marcescent; petals whitish faintly tinged with pink-lilac or flesh-color, drying stramineous, only slightly or (when small) often irregularly graduated, the wings then either a trifle shorter than the keel or longer than the banner; banner recurved through about 40 degrees, obovate-cuneate or broadly elliptic, shallowly but openly notched, (3.3) 3.5-6.5 mm. long, 2.5-3.8 mm. wide; wings 3.6-5.4 mm. long, the claws 1.4-2.3 mm., the oblong or oblong-oblanceolate, obtuse, straight or slightly incurved blades 2.1-3.7 mm. long, 1-1.6 mm. wide; keel 3.6-5 mm. long, the claws 1.4-2.5 mm., the obliquely obovate or nearly half-circular blades 2.1-3 mm. long, 1.4-2 mm. wide; anthers 0.25-0.4 mm. long." (bibref: 1814).
Fruit: "Pod ascending, sessile on the receptacle, half-elliptic or lunately elliptic in profile, 1-1.7 cm. long, 4.5-7 mm. in diameter, a little inflated but scarcely bladdery, cuneate and laterally compressed at both ends, but strongly compressed only in the triangular beak, at the middle terete or very slightly compressed, the sutures both filiform, the ventral one straight or gently concave, the dorsal one convex, the thin, canescently strigulose-pilosulous valves becoming papery but opaque, obscurely reticulate, not inflexed, the funicular flange subobsolete, not over 0.2 mm. wide; dehiscence apical, after falling, the beak narrowly gaping; ovules (3) 4-6 (7); seeds ochraceous or chestnut-brown, often purple-dotted, pitted or wrinkled, dull, 2.7-3.7 mm. long." (bibref: 1814).

Bloom Information

Bloom Color: White , Pink , Yellow , Purple , Violet
Bloom Time: Feb , Mar , Apr , May
Bloom Notes: "Petals whitish faintly tinged with pink-lilac or flesh-color, drying stramineous. February to April (May)." (bibref: 1814).

Distribution

USA: AZ , CA
Native Distribution: "Locally abundant in the Larrea zone of the Colorado Desert from Salton Sea to Borrego Valley, Imperial Valley, and along the lower Colorado from Palo Verde Valley south to Yuma Desert, southeastern California and immediately adjoining Arizona, Sonora, and Baja California." (bibref: 1814).
Native Habitat: "Dunes and open sandy plains and valley floors, 200 feet below to 1200 feet above sea level." (bibref: 1814).

Bibliography

Bibref 1814 - Atlas of North American Astragalus Volume 2 (1964) Barneby, Rupert C.

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Additional resources

USDA: Find Astragalus aridus in USDA Plants
FNA: Find Astragalus aridus in the Flora of North America (if available)
Google: Search Google for Astragalus aridus

Metadata

Record Modified: 2020-12-07
Research By: Joseph A. Marcus

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