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Astragalus chuskanus

Astragalus chuskanus Barneby & Spellenb.

San Juan Milkvetch, Chuska Mountains Milkvetch, Chuska Milkvetch

Fabaceae (Pea family)


USDA Symbol: ASCH13

USDA Native Status: L48 (N)

"Humifuse matted perennial herb with many freely branching, densely leafy stems to 3.5 (4) dm, radiating from the scarcely indurated multicipital crown of a taproot, originating at soil surface but commonly buried for more than half the length by sand moving downslope, densely softly pilosulous throughout with fine, spreading-ascending, mixed sinuous and straighter basifixed hairs to 1 mm, the foliage silvery-gray." (reslit: 2895).

"Flowering may begin as early as late May and proceeds through the summer, the first fruits forming near the beginning of July. Along the lower edge of its elevational range it is weakly sympatric with A. humistratus A. Gray var. humistratus but is otherwise entirely above that species. With this exception it was the only Astragalus noted within its area." (reslit: 2895).


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Plant Characteristics

Duration: Perennial
Habit: Herb
Leaf Arrangement: Alternate
Fruit Type: Legume
Size Notes: "Stems to 3.5 (4) dm." (reslit: 2895).
Leaf: "Stipules 2-5.5 mm, the small lowest ones early scarious, the upper herbaceous, all connate-amplexicaul, the lowest into cuplike sheath, the upper with deltate-acuminate, often squarrose blades, internally glabrous or thinly pubescent near the tip. Leaves arcuately spreading, (1) 1.5-4 cm long, the petiole more or less0.5-1.3 cm, the rachis (0.5) 1-2.5 cm. Leaflets (7) 9-15, subsessile, decrescent upward along rachis, obovate- or oblong-elliptic, abruptly acuminulate, convex ventrally, (1.5) 2.5-9 x (0.7) 1-3 (4) mm." (reslit: 2895).
Flower: "Peduncles subfiliform, 1.5-2.5 cm long, at anthesis incurved-ascending, humistrate in fruit. Racemes shortly but loosely 4-10-flowered, the flowers ascending-spreading, the axis scarcely elongating, in fruit 3-12 mm long; bracts narrowly lanceolate, 2-3.5 mm long; pedicels ascending, in fruit persistent but scarcely thickened, 0.9-1.5 mm long; bracteoles 0. Calyx about 5.5 mm long, pilosulous like the foliage with white and sometimes a few, commonly shorter, fuscous hairs, the oblique disc 0.6 mm wide, the campanulate tube 2.8-3 x 2.2 mm, ruptured by the pod, the narrowly subulate teeth 2.4-2.6 mm long. Petals whitish, fading or drying pale ochroleucous, the banner then faintly lilac-veined and often faintly blushed with lilac, the keel maculate with dull, dark purple; banner recurved through 40 degrees, narrowly obovate or subrhombic-obovate, deeply notched, 7.6-8.2 x 4 mm; wings slightly shorter, 6.8-7.1 mm, the claw 2.7 mm, the narrowly lance-elliptic, slightly incurved blade 4.6 x 1.3-1.8 mm; keel about 5.2 mm long, the claws 2.7 mm, the blades semiobovate, 2.8 x 1.7 mm, incurved through about 110 degrees to the broadly deltate, slightly porrect apex; anthers 0.3 mm; ovary pilosulous." (reslit: 2895).
Fruit: "Pod humistrately ascending, sessile, tardily disjointing from the receptacle, obliquely semi-ovoid, about 6 x 3 mm excluding the persistent style base, broadly rounded at the base, in the lower 2/3 triquetrously compressed, carinate by the concavely arcuate ventral suture, openly and shallowly sulcate dorsally, in the distal 1/3 laterally compressed and abruptly deltoid-beaked, the pale green, finally brownish chartaceous valves pilosulous with short more or less straight and contorted hairs, sometimes faintly purple-speckled, not inflexed; dehiscence apical, through the gaping beak; ovules (4) 6; seeds brown, purple-dotted, smooth, dull, 1.9-2.5 mm long." (reslit: 2895).

Bloom Information

Bloom Color: White , Yellow , Purple , Violet
Bloom Time: May , Jun , Jul , Aug , Sep
Bloom Notes: "Petals whitish, fading or drying pale ochroleucous, the banner then faintly lilac-veined and often faintly blushed with lilac, the keel maculate with dull, dark purple." (reslit: 2895).


Native Distribution: "The species is particularly common on comparatively open and dry rocky knoll tops and on rocky slopes, where it forms a seed source for plants colonizing roadbanks below (as at the type locality." (reslit: 2895).
Native Habitat: "On gentle or steep slopes of degraded Chuska Sandstone in openings in ponderosa pine, Douglas fir, and Rocky Mountain juniper above 2250 m." (reslit: 2895).

Web Reference

Webref 50 - New Mexico Rare Plants (2020) New Mexico Rare Plant Technical Council
Webref 23 - Southwest Environmental Information Network (2009) SEINet - Arizona Chapter

Research Literature


This information was provided by the Florida WIldflower Foundation.
Search More Titles in Research Literature

Additional resources

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


Record Modified: 2023-06-20
Research By: Joseph A. Marcus

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