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Floating Mat Rooted Plants  

 
Species: Myriophyllum aquaticum (Vell.) Verdc. (synonym M. brasiliense Cambess), parrotfeather milfoil, parrot's feather
Family: Holoragaceae

Parrotfeather milfoil is an easily recognized member of the milfoil family because its stiff, bright green leaves rise above the water like a forest of tiny fir trees. These emergent leaves have a feather-like shape and are arranged in whorls around the stiff stem. Introduced from South America, parrotfeather milfoil has become a nuisance in many parts of the world, often creating dense mats on the surface of shallow water or on wet soil.

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Leaf: Two types, both feather-like and finely divided. Emergent leaves: the stiff 2-5 cm long leaves are arranged in whorls of 3-6 leaves around the stem. Each leaf is divided into 12-36 leaflet pairs. Underwater leaves are often decayed, but if present, they are limp, 1.5-3.5 cm long, and are divided into 10-15 leaflet pairs per leaf.

Stem: The sturdy, sparsely branched stems grow up to 2 m long and 5 mm in diameter. They sprawl along the water surface or wet soil and rise up to 30 cm above the water.

Flower: Tiny (0.5 mm) flowers with 4 white sepals occur individually on short stalks at the base of the emergent leaves. Male and female flowers are on separate plants, but only female plants are found in North America.

Fruit: Because only female plants are found in North America, fruits are not produced here.

Root: Many, thin, from rhizomes.

Propagation: Spreads by rhizomes. Fragments easily root to colonize new areas. 

Importance of plant: Parrotfeather is an escaped ornamental and aquarium plant and often invasive where introduced. This hardy plant will survive summer droughts and winter freezes.

Distribution: Native to South America, but introduced nearly worldwide. Found in several western Washington locations. It has not been reported from eastern Washington, but should be tolerant of conditions there.

Habitat: Slow moving rivers, ditches, and shallow freshwater lakes and ponds. Will grow on wet soil along shorelines. Prefers nutrient rich conditions.

May be confused with: The submersed leaves are easily confused with Invasive Nonnative Plant Iconother milfoil species, however the stiff, finely-divided feather-like emergent leaves are distinctive.


Photographs:
Close up of Myriophyllum aquaticum, parrotfeather in lake

Line Drawings: Myriophyllum aquaticum


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