mimosa (mĭmōˈsə) [key], any tree, shrub, or herb of the genus Mimosa of the family Leguminosae (pulse family), chiefly tropical plants. They usually have feathery foliage and rounded clusters of fragrant pinkish flowers atop the branches. Mimosas are used for ornamental purposes in warm regions. The yellow-flowered plants sold as mimosa by florists are usually of the related genus Acacia (see acacia). Most widely known of the mimosas is the sensitive plant ( M. pudica ), considered a weed in the American tropics but cultivated as a greenhouse annual elsewhere because its leaves fold up and collapse under stimulus (e.g., touch, darkness, or drought) until the whole plant may assume temporarily a thoroughly wilted appearance. It is now naturalized in many warm regions and grows wild in the Gulf states. The name sensitive plant is also applied to other plants of this family that show similar movements. Mimosa is classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Leguminosae.