Lathyrus hirsutus L. (Caley pea, singletary pea)
Pl. 398 d–f; Map 1760
Plants annual, with
shallow taproot, the roots not producing tubers. Stems 15–100 cm
long, trailing, ascending, or climbing, often branched at the base, glabrous or
sparsely and inconspicuously hairy, angled or narrowly winged, the wings to 2
mm wide. Leaves with 2 leaflets, the petiole 2–4 cm long, broadly winged, the
tendrils branched. Stipules 7–20 mm long, 1–3 mm wide,
narrowly lanceolate, the basal lobe 3–10 mm long,
narrowly triangular. Leaflets 2–9 cm long, 4–18 mm wide, narrowly
elliptic to linear or oblong-lanceolate, angled at
the base, angled to a bluntly or sharply pointed tip, the midvein
sometimes extended into a minute sharp point at the very tip, glabrous.
Inflorescences of solitary flowers or clusters of 2(3) flowers, the stalk
3–10(–20) cm long, usually extending past the attachment of the flowers as a short
bristle, the flower stalks 4–6 mm long. Calyces with the tube 2–3 mm long,
glabrous or sparsely appressed-hairy, the lobes 2–4
mm long, subequal, narrowly ovate to ovate. Corollas 9–14 mm long, pink to bluish-purple, sometimes appearing bicolorous. Filaments with the fused portion 5–6 mm
long, the free portion 2–3 mm long. Ovary densely hairy, the
hairs developing pustular bases. Fruits 2–4 cm
long, 6–8 mm wide, narrowly oblong, strongly flattened, conspicuously hairy,
the hairs with pustular bases, 5–10-seeded. Seeds 3–4
mm long, globose to slightly angular, not flattened, the surface finely wrinkled, brown. 2n=14, 28. May–June.
Introduced, uncommon, mostly in the
southern portion of the state (native of Europe; introduced widely in the
southern U.S. north locally to Oregon and Michigan). Edges of bottomland and mesic upland forests; also margins of crop fields, old
fields, pastures, ditches, railroads, roadsides, and open disturbed areas.
Lathyrus hirsutus is easily recognized by the distinctive, pustular-based hairs on the ovary and fruits, along with
the narrowly winged stems and leaves with two leaflets. It is widely cultivated
in the United States for soil improvement and pasturage. This species was first
collected in Missouri in Jasper County by Ernest J. Palmer in 1949, and Steyermark (1963) knew it from only one additional specimen
collected by Viktor Mühlenbach in the city of St.
Louis. Since that time it has become much more abundant in southern Missouri,
especially in the Mississippi Lowlands Division.