Description

• Egeria densa
• Aquatic plant from South America; imported from the aquarium trade
• Has few natural predators to keep its growth in check
• When introduced to a lake it often forms dense mats that displace native aquatic plants
• These mats are unsightly, interfere with recreation, and degrade fish habitat

General Characteristics

• similar to hydrilla
• submersed aquatic weed, found in ponds, lakes, streams and rivers
• may reach 6 feet in length and are freely branching
• leaves occur in whorls of 3-6, most commonly of 4
• individual leaves are 1-1 ¼ inch long, 5 mm wide
• finally toothed leaf margins
• undersides of the leaf midribs are smooth and without teeth unlike those of hydrilla
• flowers have 3 white petals and 3 green sepals
• flowers appear at water surface on long stalks, showy flowers petals are 1/3 inch long

Description

• Hydrilla verticillata
• Introduced from Asia for use in aquariums
• Spreads by fragmentation and via transport on boats, motors, trailers, fishing nets, and other gear, and aquarium or water garden release
• Grows thick mats especially in shallow water
• Quickly takes over shallow lakes and rivers, preventing boating, fishing, hunting, and swimming
• Clogs irrigation canals

Description

• difficult to identify, sometimes confuse with Elodea or Egeria
• sharply toothed leaves in whorls of 3-8
• sometimes possess small teeth along underside of leaf midrib

Description

• Myriopyllum spicatum
• Spreads by fragmentation, currents and waves, and overland via transport on boats, motors, trailers, fishing nets, and other gear
• Grows thick mats in waters less than 15 deep
• Eradication is nearly impossible
• Can quickly take over shallow lakes and rivers, which can prevent boating, fishing, hunting, and swimming

General Characteristics

• Submersed, perennial, aquatic plan with feathery leaves arranged in whorls around the stem.
• Found growing in shallow water to 25 feet deep or more.
• Tops often turn read in color.
• Milfoil stems branch several times near the water surface.
• Erect stalks emerge above water with small reddish flowers.
• Typically 4, but sometimes 3-5 leaves, form a whorl around the stem.
• Each leaf has 12 or more pares of leaflets.

Links

Walleyes Unlimited of Montana-Eurasian Watermilfoil

Description

• Potamogeton crispus
• Perennial, rooted, submerged aquatic vascular plant native to Eurasia, Africa and Australia
• By 1950 most of the U.S. was infested by this species
• Forms dense mats which interfere with recreation and limit the growth of native aquatic plants
• In shallow lakes it can grow dense enough to affect recreational boating and fishing
• It can alter nutrient dynamics of a fertile lake causing heavy summer algae blooms

General Characteristics

• leaves are alternate with crinkled leaves that are finely toothed
• most often found in ponds with fertile, hard water
• flower spikes often stick up above the water surface during spring
• tolerates low light and may grow in deep water

Description

• Butomus umbellatus
• An emergent in shallow areas of lakes, flowering rush has umbellate pink flowers and grows to 3 feet tall on triangular stems
• Also a submersed form which can grow in water 10 feet deep
• Use as an ornamental provided a route to the Midwest and expedited it’s spread westward to the Idaho panhandle and Northwestern Montana
• In Northwestern Montana it is reported to be out-competing the native willows and cattails

General Characteristics

• flowers grow in umbrella shaped clusters and each individual flower has 3 whitish pink petals
• plants only produce flowers in very shallow water or on dry sites
• green stems resemble bulrushes but are triangular in cross section
• leaf tips may be spirally twisted
• along shores, has erect leaves and grows to about 3 feet in height
• forms an extensive root system that can break into new plants if disturbed