Astragalus lotiflorus Hook. (low milk vetch, lotus milk vetch)
Pl. 389 i–k; Map 1716
Plants perennial herbs (but sometimes
flowering the first year), with a taproot, sometimes below a branched caudex.
Stems 1–8(–12) cm long, sometimes apparently absent and the nodes short and
densely clustered, mostly prostrate, but the inner stems often loosely
ascending to erect, several per plant, unbranched or more commonly
few-branched, green or purplish-tinged, glabrous toward the base, moderately to
more commonly densely pubescent with branched hairs, these appressed and with 2
opposite branches, thus appearing as a straight line attached near the midpoint
(best observed carefully with magnification). Leaves with the petiole 10–30 mm
long, with 9–15(–21) leaflets, the rachis 4–9 cm long. Stipules 2–8 mm long,
free from the petiole and not sheathing the stem, narrowly lanceolate to ovate,
tapered to a sharply pointed tip, membranous when young, papery at maturity.
Leaflets 4–15 mm long, 2–6 mm wide, narrowly oblanceolate to lanceolate,
elliptic, or obovate, rounded to bluntly pointed at the tip, the upper surface
sparsely branched-hairy, the undersurface moderately to densely branched-hairy
(the foliage leaves similar to those of the stem). Inflorescence of 2 types
(produced on separate plants or those with cleistogamous flowers produced late
in the season only from basal nodes), those with open flowers short, appearing
as capitate clusters or short, dense, often more or less ovoid, spikelike
racemes, 3–5 cm long, the stalk 2–6(–9) cm long, with 5–11 flowers; those with
cleistogamous flowers appearing as capitate clusters or very short, spikelike
racemes, 1–3 cm long, the stalk absent or to 2 cm long, with 2–4 flowers.
Bracts 2–3 mm long, hairy. Flowers mostly spreading, the stalks 0.5–2.5 mm
long, hairy. Calyces with the tube 2–3 mm long, narrowly bell-shaped, usually
slightly pouched, densely hairy, the lobes 2–3 mm long, narrowly triangular.
Corollas of open flowers well-developed, light greenish yellow, the banner 8–11
mm long, 4–5 mm wide, somewhat curved or bent upward, the wings 7–9 mm long,
the keel 6–7 mm long; those of cleistogamous flowers reduced, not fully
opening, white to pale cream-colored, the banner 4–7 mm long, the wings and
keel 4–6 mm long. Stamens with the fused portion 4–5 mm long, the free portion
1.0–1.5 mm long. Styles 4–6 mm long. Fruits 16–25 mm long, 6–7 mm wide,
cylindric, short-tapered to a short beak at the tip, straight or nearly so, not
or only slightly inflated, leathery at maturity, ascending, 1-locular, hairy,
sometimes reddish- to purplish-tinged when young, dehiscent from the tip,
sometimes tardily or after being shed. Seeds 1.8–2.5 mm long, the surface brown
to reddish grown, coarsely and bluntly wrinkled. 2n=26. April–May.
Uncommon, known only from Holt and
Atchison Counties (Montana to Minnesota south to New Mexico, Texas, and
Arkansas; Canada). Loess hill prairies.