Mimosa pudica

Native from Mexico through tropical America, this herb or low, straggling subshrub grows close to the ground. Its leaflets fold within seconds when touched, and the leaf stalks can droop. Electrical and calcium signals trigger water loss from specialized cells at the leaf joints, causing this rapid movement. Experiments have shown that the movement can help defend the plant against insect feeding. Its pink flower heads owe much of their color to the long stamen filaments, and its seedpods have bristly margins. Outside its native range, it is naturalized in Singapore and invasive along parts of the Queensland coast in Australia, where it competes with tropical crops and pasture plants. Photographed in the western Andes mountain range of Colombia.