Trifolium resupinatum

Herbs annual, 20–60 cm, gla­brous or glabrescent. Stems ascending, erect, or procumbent, branched. Leaves palmate; stip­ules lanceolate or ovate, 0.5–1.8 cm, margins entire, apex acuminate-filiform; petiole 0.5–20 cm; petiolules to 1 mm; leaflets 3, blades obovate, ovate, elliptic, or rhombic, 1–3 × 0.5–3 cm, base cuneate, veins moderately prominent, margins spinulose-dentate, apex rounded or broadly acute, surfaces hairy abaxially, glabrous adaxially. Peduncles 1–6 cm. Inflorescences axillary, 15–30-flowered, subglobose to globose, flowers resupinate, forming stellate-spreading clusters in fruit, 0.5–1.6 × 0.8–1.5 cm; involucres a narrow rim, 0.2 mm. Pedicels slightly reflexed, to 0.5 mm; bracteoles minute or absent. Flowers 5–6 mm; calyx tubular-campanulate, inflated in fruit, markedly asymmetric-bilabiate, slit between adaxial lobes, 2.5–3 mm, 8–11 mm in fruit, hairy, short-hairy or glabrescent in fruit, veins 10, connected by lateral veins, tube 2 mm, 7–9 mm in fruit, lobes green, erect, unequal, triangular, divergent, linear-lanceolate, unequal in fruit, orifice open; corolla pink to purple, 5–8 mm, banner oblong, 5–8 × 2 mm, apex emarginate to crenulate. Legumes lenticular, 1.8–2.2 mm. Seeds 1, ovoid, dark purple, olive green, yellow, or reddish brown, 1.5–1.9 mm, smooth, dull. 2n = 14, 16, 32.

Phenology: Flowering Mar–May.
Habitat: Wet meadows, lawns, road­sides, fields, waste places.
Elevation: 0–700 m.

Distribution

• Generated Map
• Legacy Map

Introduced; Ont., Ala., Ark., Calif., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Miss., Mo., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Vt., Va., Wash., W.Va., Wis., c, s Europe, sw Asia, n Africa, intro­duced also in s South America (Argentina, Uruguay), s Africa, Pacific Islands (Hawaii, New Zealand), Australia.

Discussion

Widespread use of Trifolium resupinatum as a forage crop began in the late 1920s, after it began to flourish in Louisiana following a flood of the Mississippi River (E. A. Hollowell 1943). It is used in the southern United States as a pasture plant and for production of hay, and has spread widely from cultivation.

Reports of Trifolium resupinatum for New Brunswick and Quebec are based on old collections; since the species has not been recollected for many years in either province, they are excluded here.

Selected References

None.

Lower Taxa

None.