Mimosa pigra

Name and classification

Mimosa pigra L. var. pigra
Family Fabaceae, Subfamily Mimosoideae

Common names

catclaw mimosa

Disseminule

one-seeded fruit segment

Description

Fruit a craspedium; craspedia linear-oblong, compressed, straight or curving slightly, 4–7.5 cm long, 8–11 mm wide, ca. 2 mm thick. Sessile, apex mucronate, margins straight. Densely bristly. At maturity narrow 1-seeded fruit segments (valves) split transversely and separate from the persistent sutures. Valves 20–25.

Seeds oblong in outline, umbo absent, 4–8 mm long, 2–4 mm wide, 1.75–2 mm thick, depressed on faces, irregularly oblong in cross section. Dull, semiglossy, smooth. Pleurogram open, distinctly wide and closely following margin; pleurograms on each face nearly connected at base. Lens elliptic, same color or lighter than testa, surrounded by darker halo, flush or slightly raised. Embryo investing, cotyledons much longer than radicle.

Identification considerations

The bristly craspedium and single-seeded craspedium segments are distinctive. Compare with Mimosa diplotricha and with seeds of Prosopis.

Seeds distinctly oblong, with a wide pleurogram.

Distribution

United States, Mexico through Central America and the Antilles; South America: Colombia, Peru, and Brazil to northern Argentina. In the eastern hemisphere, Africa: Ghana, Madagascar, Mauritius, Nigeria, South Africa; Asia: Cambodia, Indonesia, Philippines, Sri Lanka, Taiwan, Thailand; Oceania: Australia, Fiji, Hawaii, Polynesia

native to tropical America

Habitat

wet places in the humid and subhumid tropics, such as drainage ditches, wetlands, riverbanks, and lowland fields

General information

Mimosa pigra is a prickly shrub, 3–5 m tall, that forms impenetrable thickets, making areas inaccessible to man and animals. Reproduction is by seed and vegetatively from cut stems. The hairy one-seeded craspedium segments stick to animal fur and are eaten by animals. But more significantly, the segments float, allowing the plant to be dispersed by flood waters and along river systems, enabling it to rapidly colonize large wetland areas. This shrub interferes with irrigation projects and smothers pasture lands.

seeds

seeds

lens and hilum of seed

lens and hilum of seed

craspedia

craspedia

A, one-seeded fruit segment; B, seed; C, longitudinal section of seed showing embryo; D, transection of seed; drawing by Lynda E. Chandler

A, one-seeded fruit segment; B, seed; C, longitudinal section of seed showing embryo; D, transection of seed; drawing by Lynda E. Chandler