Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: parrot feather

Synonyms and Other Names: Brazilian watermilfoil, parrot’s feather, parrot-feather, parrotfeather, parrot feather watermilfoil, Enydria aquatica (Vell.), Myriophyllum brasiliense (Camb.), Myriophyllum proserpinacoides (Gillies ex Hook. and Arn.)

Taxonomy: available through www.itis.gov

Identification: Parrot feather (Myriophyllum aquaticum) is heterophyllous, meaning it has both an emergent and submersed leaf form. Emergent leaves are whorled, stiff, and usually have 20 or more linear divisions (10 leaflet pairs) on each leaf (Godfrey and Wooten 1981). The leaves appear feather-like and grayish green and can extend to 30 cm above the water surface.

The submersed shoots, similar to those of Eurasian watermilfoil (M. spicatum), are comprised of whorls of four to six filamentous, pectinate leaves, 1.5 to 3.5 cm long, arising from each node (Mason 1957, Washington State Department of Ecology 2011). Submersed leaves are reddish orange. When the submersed shoots reach the water surface, plant growth changes and begins to creep along the water surface with extensive branching from nodes followed by vertical growth of emergent stems (Moreira et al. 1999).

Small, white flowers occur in the leaf axils on the emergent shoots and are approximately 1/16 inch long (Washington State Department of Ecology 2011). Parrot feather lacks structures for storage, dispersal, and perennation (e.g., tubers, turions, and winter buds), and therefore stolons serve all these functions (Sytsma and Anderson 1993).

Size: leaves 1.5 to 5 cm, stems up to 5 feet.

Native Range: Myriophyllum aquaticum is a native of the Amazon River basin in South America, including Brazil, Bolivia, Ecuador, Peru, as well as Argentina, Chile, and Paraguay (Washington State Department of Ecology 2011). It prefers to inhabit subtropical regions (Fernandez et al. 1993).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Parrot feather grows well in shallow wetlands, slow moving streams, irrigation reservoirs or canals, edges of lakes, ponds, sloughs, or backwaters (Sutton 1985). Although it can grow in moist soil and tolerates a wide-range of water levels, parrot feather grows most rapidly in higher water levels (but has been documented in depths up to 16 ft; Banfield 2008) and high-nutrient environments (Hussner et al. 2009; Sutton 1985; Sytsma and Anderson 1993). Parrot feather requires rooting in bottom sediments, in habitats where light can penetrate to the bottom favor growth and colonization. Parrot feather thrives under slightly alkaline conditions (pH range 6.8-8.0), prefers temperatures between 16-23°C, and can withstand a water hardness level between 50-200 ppm (Federation of New Zealand Aquatic Societies, in Mabulu 2005). This species displays photosynthetic activity at pH levels of 6 to 8.5, depths of 0 to 10 meters, and temperatures from 10°C to 30°C, though it can survive even broader ranges (Robinson 2003; WIDNR 2011). It can also survive frequent inundation of salt water as long as concentrations remain below 4 ppt (Sutton 1985). Parrot feather is not seriously affected by frost (Moreira et al. 1999); however, a hard or extended period of frost may kill emergent shoots in northern latitudes (WIDNR 2011). Parrot feather can survive winters in its submersed form and begin growth when water temperatures reach 7°C (Moreira et al. 1999). Nevertheless, invasion tends to fail in areas with severe winters, because parrot feather does not store phosphorus or carbon in its rhizomes (Mabulu 2005).

Parrot feather is a dioecious species, however only pistillate (female) plants are found outside of South America. Staminate (male) plants are rare even in native populations of South America (Orchard 1981). For this reason, seed production is not known to occur (Aiken 1981) and reproduction is exclusively vegetative in North America (Orchard 1981). Reproduction occurs by fragmentation of emergent and/or submersed shoots, roots, rhizomes, or attached plant fragments (Center for Aquatic and Invasive Plants, UF/IFAS 2010; Les and Mehrhoff 1999; Mabulu 2005).

Parrot feather has an annual growth pattern, forming shoots in spring from overwintering rhizomes as water temperature increases. Rhizomes provide support for adventitious roots and buoyancy for emergent summer growth. Flowers usually appear in spring, or in fall for some plants. The plant usually dies back to its rhizomes in the autumn (Mabulu 2005).

Means of Introduction: Escaped ornamental pond plant.

Status: Established in North America.

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health	Other

Dense infestations can rapidly overtake small ponds and sloughs, impeding water flow resulting in increased flood duration and intensity. Parrotfeather may also out-compete more desirable native macrophytes. Little information exists on the direct impact that parrotfeather has on fish and wildlife. Dense beds of parrotfeather have resulted in reductions in dissolved oxygen in the water column, which may be detrimental to fish (Fonseca 1984 cited in Moreira et al. 1999). Parrotfeather growth can inhibit the growth of more desirable plant species such as pondweeds and coontail (Ferreira and Moreira 1994), which are readily utilized by waterfowl as food items (Wersal et al. 2005). A strong correlation was determined between the density of parrotfeather growth and the presence of mosquito eggs and larvae (Orr and Resh 1989), which may lead to increases in mosquito born diseases that could infect wildlife and humans.

Remarks:
 

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Other Resources:
UF/IFAS Center for Aquatic and Invasive Plants - Myriophyllum aquaticum

ISSG Database: Myriophyllum aquaticum

State of Washington Department of Ecology

US Fish and Wildlife Service Ecological Risk Screening Summary for Myriophyllum aquaticum

Author: Wersal, R.M., E. Baker, J. Larson, K. Dettloff, A.J. Fusaro, D.D. Thayer, and I.A. Pfingsten

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.