FULL SCIENTIFIC NAME
Myriophyllum aquaticum (Vell.) Verdc.
FAMILY NAME COMMON
FAMILY SCIENTIFIC NAME
Close-up of plant
Synonyms: Enydria aquatica Vell.
Myriophyllum brasiliense Camb.
Myriophyllum proserpinacoides Gillies ex Hook. & Arn.
Myriophyllum aquaticum is an herbaceous aquatic plant that can grow 2-5 m (6.5-16 ft.) in length. The bluish-green stems are stout. The numerous leaves of this plant are pinnately dissected and arranged in whorls of 4 to 6 around the stem. They have both emergent and submerged leaves. The emergent leaves can be up to 30 cm (1 ft.) out of the water. They measure 2-5 cm (0.75-2 in.) long and have 6-18 divisions per leaf. The submerged leaves are 1.5-3.5 cm (0.5-1.25 in.) long and have 20-30 divisions per leaf. The flowers are located axillary to slightly modified leaves on the emergent inflorescences. They are positioned between two bracts and measure 1.5 mm (0.06 in.) long. The flowers do not have petals, but have white sepals. The plants are dioecious, and only female plants have been reported in the United States. The fruits of this plant are 1.5-2 mm (0.07 in.) long. Page References Crow & Hellquist 194, Gleason & Cronquist 308, Holmgren 289, Magee & Ahles 778. See reference section below for full citations.
Since all the known Myriophyllum aquaticum plants in the United States are female, the only means of reproduction for this plant in the U.S. is by fragmentation. Plant fragments can move downstream with the current, or attach to boats and animals.
Myriophyllum aquaticum is native to South America along the Amazon River. It has been introduced into South Africa, New Zealand, Australia, Japan and parts of Europe. In the United States it has been reported in the west from Washington, Oregon, California, Hawaii, Idaho, Montana, Arizona and New Mexico. It has been reported from Massachusetts to Florida and west to Kansas, Oklahoma and Texas. In New England it has been reported from Connecticut and Massachusetts.
HISTORY OF INTRODUCTION IN NEW ENGLAND
Myriophyllum aquaticum was most likely introduced in the late 1800's for aquaria and water gardening. The first known specimen of this plant was collected in 1890 from New Jersey. It also became established in the early 1900's around Washington, D.C. because of water gardening. This plant reported in 1929 from southeastern New York (Long Island). In 1946 the first report in New England came from West Lake in Guilford, Connecticut. In Massachusetts it has been reported from Cape Cod.
HABITATS IN NEW ENGLAND,Aquatic,Lake or Pond,River or Stream,Yard or Garden
Myriophyllum aquaticum is found in lakes, ponds and quiet streams. The emergent form of this plant can survive on mudflats, indicating that it can tolerate water fluctuations. Myriophyllum aquaticum appears to thrive in high nutrient situations.
Myriophyllum aquaticum has not yet been reported from the northern parts of New England, and its potential range is yet to be determined. In more southern regions, this plant forms monocultures that clog waterways, impeding recreational and commercial boating activities. These monocultures also disrupt the growth of native aquatic plants and provide breeding areas for mosquitoes. Myriophyllum aquaticum is a common water garden plant, which has the potential to escape into local waterways. The control of this plant is expensive, with costs in the order of tens of thousands of dollars in Washington state alone.
Documentation required: Herbarium specimen or mounted snippet of the branch.
Best time for documentation: Summer, fall.
Integrated Taxonomic Information System
General information and map
Virginia Native Plant Society
Fact sheet with description and control information
Center for Aquatic and Invasive Plants, University of Florida
General information and photographs
North Carolina State University
Fact sheet with description and images
King County Noxious Weeds
Description and illustrations
Washington State Department of Ecology
General information including control
Pacific Island Ecosystems at Risk
Description and control information
Bossard, C.C., J.M. Randall, M.C. Hoshovsky, M.C. 2000. Invasive plants of California's wildlands. University of California Press, Berkeley, California. Chambers, P.A., J.W. Barko, C.S. Smith. 1993. Evaluation of invasions and declines of submersed aquatic macrophytes. Journal of Aquatic Plant Management 31: 218-220. Cilliers, C.J. 1999. Lysathia n. sp (Coleoptera: Chrysomelidae), a host-specific beetle for the control of the aquatic weed Myriophyllum aquaticum (Haloragaceae) in South Africa. Hydrobiologia 415: 271-276. Cilliers, C.J. 1999. Biological control of parrot's feather, Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae), in South Africa. African Entomology 113-118. Cronk, Q.C.B. and J.L. Fuller. 1995. Plant invaders. Chapman & Hall, London. Crow G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol 1. University of Wisconsin Press, Madison. Fischer, B. 1992. The Grower's Weed Identification Handbook. Publication 4030. University of California, Division of Agriculture and Natural Resources, California. Gleason H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York. Holmgren N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York. Les, D.H. and L.J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: a historical perspective. Biological Invasions 1:281-300. Magee D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst. USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.