Vicia hirsuta (L.) Gray (tiny vetch, hairy vetch)

Endiusa hirsuta (L.) Alefield

Ervum hirsutum L.

Map 1827

Plants annual, with short taproots. Stems 20–70 cm long, loosely ascending to spreading or climbing, glabrous or sparsely and finely hairy. Leaves with (8)10–18 leaflets, the petiole absent or to 2 mm long, the tendrils mostly branched. Stipules 2–5 mm long, lacking a glandular spot, deeply 2–4-lobed, the margins otherwise entire or sharply few-toothed. Leaflets 5–14(–20) mm long, 1–3(–4) mm wide, those of the lower leaves often somewhat shorter than those of the upper leaves, linear to narrowly elliptic or narrowly oblong, angled or tapered at the base, truncate or slightly to broadly notched at the tip, the midvein often extended as a minute, sharp point at the very tip, the surfaces glabrous or sparsely and finely hairy. Inflorescences short racemes, the stalk 1.0–2.5 cm long, the flowers (2–)3–5(–8), each with a stalk 1–2 mm long. Calyces finely short-hairy, the tube 1.0–1.5 mm long, the base not or only slightly oblique, not pouched, the attachment appearing basal, the lobes 1.5–2.0 mm long, subequal (the lowermost only slightly longer than the other lobes), narrowly triangular. Corollas 2.5–4.5 mm long, pale blue to lavender or white, the keel sometimes slightly darker toward the tip, the banner somewhat curved upward, moderately to strongly curved around the wings and keel. Stamens with the fused portion 1.5–2.5 mm long, the free portion 0.5–1.0 mm long. Style with a few short hairs on the lower side at the tip. Fruits 6–10 mm long, 3–5 mm wide, sessile, finely hairy, brown to black at maturity, (1)2(3)-seeded. Seeds 1.5–2.5 mm long, brownish yellow to reddish brown and with strong, darker mottling (occasionally appearing nearly solid dark purplish brown), more or less circular in outline, not flattened or somewhat flattened, the attachment scar not raised, dark brown, extending less than 1/4 the circumference of the seed, obscured by the persistent, brown stalk. 2n=14. May–June.

Introduced, uncommon in the Mississippi Lowlands Division (native of Europe; introduced widely in the U. S., Canada). Sand prairies; also fallow fields, roadsides, and open disturbed areas.

Steyermark (1963) reported this species from railroads in the St. Louis area. However, Mühlenbach (1979) noted that these collections were misdetermined and instead represented specimens of V. villosa ssp. varia (as V. dasycarpa). The presence of V. hirsuta in Missouri subsequently was first-confirmed by a collection made by Jay Raveill in 1985 in Dunklin County.

Vicia hirsuta is recognized by the leaves with several pairs of narrow leaflets, sharply lobed stipules, small flowers, nearly glabrous styles, hairy, mostly 2-seeded fruits, and seeds with a persistent attachment stalk. Because of these distinctive characters it has sometimes been treated historically as a separate genus (Gunn, 1979). The petals are small and shed early, and the fruit begins to develop before the flower is fully open, features indicative of self-fertilization.