Wolffia arrhiza Wolffia arrhiza is a species of flowering plant in the family Araceae. It is the smallest flowering plant on Earth. It is native to Europe, Africa, and parts of Asia, and is widely distributed worldwide. It grows in calm freshwater bodies such as ponds, lakes, and slow-moving streams. The plant is a tiny, free-floating, oval-shaped green thallus, 0.5–1.5 mm long, without roots or leaves. It reproduces primarily vegetatively. It is rich in protein and is used as food in some regions of Asia.