Submersed Plants

 
Species: Myriophyllum quitense Kunth (synonym M. elatinoides Gaud.), Andian milfoil, waterwort water-milfoil, Elatine water-milfoil
Family: Haloragaceae

Andean milfoil is a native plant which usually grows in cold, clear lakes and rivers. Like the other aquatic milfoils, it has finely-divided, feather-like underwater leaves and emergent flower stalks. Unlike other milfoils, the plant sometimes forms multiple flower stalks The above water leaves that grow on the flowering stalk are nearly triangular in outline and have small teeth along the leaf margins. Andean milfoil has an unusual native distribution, being found along the mountainous western half of both North and South America.

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Leaf: Two types. Submersed leaves: feather-like and arranged in whorls of 2-4 (occasionally 5) around the stem. The leaves are 1.5-4 cm long to 2 cm wide with 5-10 leaflet pairs per leaf. The first submersed leaves at the stem base of new shoots are small, entire, and opposite. Emergent leaves: blue-green to reddish-tinted leaves are arranged in whorls of 3-4 leaves around the flower spike. Each is 0.5-1 cm long, oval to triangular shaped, and toothed along the leaf to half way to the midrib, becoming less toothed toward the leaf tip.

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


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