Stem: The cylindrical stem is 1-4 m long and is 2-4 mm in diameter at the base. Each stem sometimes bears multiple flower stalks. 

Flower: Tiny flowers (0.7-1.2 mm long) have 4 sepals and 4 petals and are located at the base of the emergent leaves. The male flowers are located near top of the flower stalk; the female flowers near the base. Andean milfoil often flowers in August and September; later than other aquatic milfoils.

Fruit: The olive brown, squarish fruit is 1.7 mm long and seldom found.

Root: Numerous whitish rhizomes form roots at the joints. The roots are very branched.

Propagation: Seeds and plant fragments. Andean milfoil will also produce winterbuds, although it overwinters in an evergreen condition.

Importance of plant: Provides habitat for aquatic animals and stabilizes sediments.

Distribution: South America, Mexico, western North America, and Prince Edward Island. Not common in Washington.

Habitat: Freshwater lakes, rivers, and streams. Usually in cold nutrient-poor water. 

May be confused with: When the emergent flowering stalks are absent, Andean milfoil is easily confused with other milfoils, especially northern milfoil (Myriophyllum sibiricum). Usually chemical analysis is necessary to be certain of the identity of non-flowering aquatic milfoil plants.

Photographs: Myriophyllum quitense, Myriophyllum quitense showing opposite, entire leaves at the stem base. 

Line Drawings: None available