Myriophyllum aquaticum

Family

Haloragaceae – Watermilfoil family

Other Names

Brazilian watermilfoil

USDA Code

MYAQ2

Legal Status

Colorado Noxious Weed List A

Identification

Lifecycle

Perennial emergent aquatic

Growth Form

Plants are up to 5 foot tall, emerges 1 foot above the water surface.  May spread horizontally 16 feet

Flower

Flowers are white, inconspicuous, in leaf axils
Flowers May-September

Seeds/Fruit

Seed not produced in North America

Leaves

Leaves in whorls of 4-6, feather-like, each deeply divided into 10-15 pairs.   Submersed leaves ½-1¼ inches long and ½ inch wide.  Emergent leaves ¾-2 inches long and ½ inch wide

Stems

Stems rigid, thick, to 15 feet long.  May form mats

Roots

Rhizomes with secondary adventitious roots

Impacts

Agricultural

Alters flow of water.  May contribute to increased severity of flooding

Ecological

Displaces native plants.  Depletes oxygen levels in water

Human

May create habitat for mosquitoes

Habitat and Distribution

General requirements

Found in lakes, ponds, canals and slow-moving water

Distribution

Not known in Colorado

Historical

Native to South America

Biology/Ecology

Mode of reproduction

Reproduces by plant fragments.  Only female plants found in North America

Dispersal

Plant fragments, rhizomes, human