Northern Watermilfoil (Myriophyllum exalbescens)

Northern watermilfoil illustration Northern watermilfoil photo


Location: Grows entirely underwater in depths from 1 to 20 feet.

Description: Dark-green, feathery leaves are grouped in fours around a hollow stem that is usually buff- or pinkish-colored; leaves are comprised of 5 to 10 pairs of leaflets.

Hints to identify: Northern watermilfoil is often mistaken for coontail or Eurasian watermilfoil, but it does not branch at the surface as much as Eurasian watermilfoil does; northern typically has half as many leaflet pairs as Eurasian has; northern leaves are rigid when removed from the water, but Eurasian leaves are limp when out of water. The northern species also forms winter buds (groups of small, dark, brittle leaves) in late fall and winter, but the Eurasian variety does not.

Importance of plant: Provides cover for fish and invertebrates; supports insects and other small animals eaten by fish; waterfowl occasionally eat the fruit and foliage.

Management strategy: See DNR regulations. When control is absolutely necessary, hand-pulling, raking, or cutting can be effective in small infestations. Collect and dispose of all fragments----they can regenerate into new plants. Treatment with aquatic herbicides can be effective.