Lepidaploa gracilis (Slender Ironweed)

Native to tropical South America, this erect subshrub grows about two to five feet tall. Its slender stems are longitudinally ridged, and the young tips are hairy. Narrow, lance-shaped leaves have short stalks and pale, woolly undersides; their margins are entire or faintly toothed. Small flower heads occur singly or in pairs along leafy flowering branches. Each head contains numerous purple florets surrounded by several rows of bracts. Tiny hairy fruits develop with a two-tiered tuft of bristles that aids dispersal. Photographed in Colombia.