Aquatic & Riparian Noxious Weeds

Aquatic weeds can be emerged, submerged or floating. An emerging plant is rooted underwater and has a structure emerging beyond the surface of the water (often on a stem, for flowers to be pollinated). A submerged aquatic plant exists entirely (or almost entirely) under the surface of the water (it may grow to touch the surface or produce near-surface flowers, such as Brazilian Elodea), and a floating plant will have roots in the underwater sediment but be attached to a leaf "floating" on the surface of the water.

Riparian weeds grow along the banks of a waterway extending along the edge of the floodplain. It is not uncommon for some riparian weeds to have submerged bases, but they are not categorized as "aquatic weeds," if their living totally outside the water is possible.

Aquatic and riparian weeds pose a variety of risks and create numerous issues including flooding, habitat degradation, impeding water flow, decreasing recreational opportunities, and much more. Often forgotten about and less visually apparent, aquatic weeds frequently go under the radar. It is, however, important for the public to be aware of the presence of aquatic noxious weeds in the water bodies they visit and take measures to prevent their spread!

The PlayCleanGo campaign provides excellent information on necessary precautions and procedures that should be taken by all, in order to reduce the spread of noxious aquatic weeds.Stop Aquatic Hitchhikers also provides a variety of resources for people to help stop the spread of these aquatic invaders.

Aquatic Noxious Weeds of Concern in Lewis County

brazilian elodea

Brazilian Elodea

Eurasian watermilfoil

Eurasian Watermilfoil





Riparian Noxious Weeds


Knotweed (Bohemian, Giant, Japanese)


Flowering Rush

purple loosestrife

Purple Loosestrife

yellowflag iris

Yellowflag Iris

Lewis County Noxious weed control has ongoing projects focused on addressing Knotweed, Eurasian Watermilfoil, Brazilian Elodea, and Purple Loosestrife in particular areas of the county.