Herbs or subshrubs, prostrate or sprawling, 0.5–0.8 m, armed. Stems ribbed, usually glabrous, rarely puberulent; prickles along ribs, recurved. Leaves: stipules linear to narrowly lanceolate, 4.5–8 mm, glabrous; petiole 2–4 cm; primary rachis 3–7 cm; pinnae 4–7(or 8) pairs; leaflets 11–16 pairs, blades obliquely oblong to elliptic, 4.5–6 × 1.8–2.5 mm, margins ciliate, reticulate veins prominent abaxially, apex acute, mucronate, surfaces glabrous. Peduncles 3.5–9.5 cm. Inflorescences 90–140-flowered, axillary, globose capitula, solitary and in racemes 130–200 mm, 20–30 mm diam.; bracts spatulate, 1/3–1/2 corolla length. Pedicels 0.2–0.9 mm. Flowers bisexual and staminate; calyx campanulate, lobes 5(or 6), 1/10 corolla length; corolla purplish pink, glabrous, lobes 5(or 6), 1/3–1/2 corolla length; stamens 10(or 12), filaments connate at bases, pink; ovary stipitate, glabrous; style attenuate at apex; stigma narrowly cupuliform or tubular. Legumes sessile, straight or curved, linear, 40–120 × 3–4.5 mm, not constricted between seeds, valves entire, 1–2.5 mm wide, margin 2–4 mm wide, prickly, prickles sometimes connate at bases, apex rostrate, rostrum 5–20 mm, faces glabrous. Seeds 4–15, reddish brown, lenticular or rhomboid, 4.2 × 3.2 × 2 mm, testa porous, fissural line 90%.

Phenology: Flowering Apr–Oct; fruiting Jun–Oct.
Habitat: Woods, mesic to xeric prairies, dry woods, oak woods.
Elevation: 0–1300 m.

Distribution

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Ark., Colo., D.C., Ill., Iowa, Kans., La., Mich., Mo., Nebr., N.Mex., N.Dak., Okla., Pa., S.Dak., Tex., Wis.

Discussion

Mimosa nuttallii is the most widespread species of the genus in the United States. It superficially resembles M. hystricina, but the two are largely allopatric (B. L. Turner 1994e), although D. Isely (1973) reported occasional intermediates between these two closely related taxa in northern Louisiana. Furthermore, Isely (1986) considered M. hystricina as a variety of M. nuttallii.

Selected References

None.

Lower Taxa

None.