Myriophyllum aquaticum
parrot feather watermilfoil

Myriophyllum aquaticum
Myriophyllum aquaticum
Photo courtesy Renee Brecht
Britton & Brown
Botanical name: Myriophyllum aquaticum
Common name: parrot feather watermilfoil
Group: dicot
Family: Haloragaceae
Growth type: forb/herb
Duration: perennial
Origin: introduced; highly invasive, noxious in several states and banned in several countries
Plant height: up to a foot above the water surface
Foliage: feather like leaves arranged around the stems in whorls of four to six
Habitat: used in aquaria and outdoor ponds; escaped or disposed of into waterways such as freshwater lakes, ponds, streams, canals
Range in New Jersey: Cumberland County on Menantico; known from Gloucester County
Heritage ranking, if any: n/a
Misc. An extremely invasive weed from South America. All plants outside of South America are female and thus do not reproduce by seed. Reproduction is via heavy rhizomes and mechanical fragmentation.

Problems caused by M. aquaticum include physical and chemical changes to lakes and streams; shading of algae, a loss of oxygen resulting in loss of aquatic life; increase in mosquito larvae habitat; clogging of irrigation and drainage canals; and lost recreational opportunities such as kayaking, canoeing, and fishing.

This plant has been found on the upper stretches of the Menantico River. Manual removal of the plant is difficult, as this plant spreads through fragmentation. Use of herbicides is difficult because the plant has a waxy cuticle, requiring a wetting agent. The weight of the herbicide causes the plant to collapse and the herbicide often washes off of the plant before the herbicide works.

Planting of this plant in outdoor ponds and aquaria is highly discouraged.

Reference sources:

State of Washington Dep't of Ecology
Massachusetts Department of Conservation and Recreation
British Centre for Ecology & Hydrology Centre for Aquatic Plant Management
Invasive Species Ireland
UK Invasive Weeds