Mike Naylor, MD DNR

Parrot Feather Watermilfoil
Myriophyllum aquaticum

Origin: South America

Background
Parrotfeather was introduced to the United States in the Washington, DC area about 1890. Commonly sold for aquaria and aquatic gardens, it has escaped to some freshwater ponds in this region.

Distribution and Ecological Threat
Parrotfeather occurs in at least 26 states throughout the United States, and is limited to non-tidal fresh waters. It can form dense mats and compete with native aquatic plants, especially in shallow ponds. It also provides habitat for mosquito larvae, impedes boats and clogs drainage ditches.

Description and Biology

• Plant: aquatic plant with stout stems; both stems and submerged leaves may be reddish tinted; gray-green tips of the stems with leaves may protrude above the water.
• Leaves: are finely divided, pale whitish green in color, in whorls of mostly five with smooth leaf margins.
• Flowers, fruits and seeds: flowers in axils of submerged leaves; fruits up to 1/8 inch long.
• Spreads: vegetatively from whole plants or fragments; it can be dispersed by people dumping aquaria into rivers and ponds and by animals carrying fruits and fragments on their bodies.
• Look-alikes: coontail (Ceratophyllum demersum), hydrilla (Hydrilla verticillata), Eurasian watermilfoil (Myriophyllum spicatum, non-native, invasive), and possibly elodeas.

Prevention and Control
Attempting control by manual or mechanical means tends to spread the plants and should only be conducted in small, contained water bodies. Draining a pond in the summer achieved control in one instance, but draining may not achieve control in winter. Control with herbicides is difficult because the emergent stems and leaves have a waxy cuticle that repels herbicides. Research into biological control of parrotfeather is ongoing.

Peter Bergstrom, USFWS

Peter Bergstrom, USFWS

Peter Bergstrom, USFWS

Native Alternatives
Some aquatic nurseries carry native and non-invasive alternatives. However, due to the similarity in appearance among aquatic plants to the untrained eye, they are easily confused. Contact your state natural resource agency, native plant society or other resource (see reference section) for assistance in locating species appropriate to your location and site conditions.

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Publication by USFWS BayScapes Conservation Landscaping Program
http://www.nps.gov/plants/alien/pubs/midatlantic/myaq.htm
Last updated: 7 October 2004