Ageratum conyzoides (billygoat-weed, chick weed, goatweed, whiteweed) is native to Tropical America, especially Brazil, and considered an invasive weed in many other regions. Herb 0.5–1 m. high, with ovate leaves 2–6 cm long, and flowers are white to mauve. In Vietnamese, the plant is called cứt lợn (meaning "pig feces") due to its growth in dirty areas.