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Aquatic Plants - #5 Most Unwanted AIS
Aquatic Plants

Aquatic plants, such as Hydrilla, Eurasian watermilfoil, and Curly Pondweed can have huge impacts on fishing, boating, and even swimming in Wyoming waters. Be sure you are not spreading these unwanted plants to Wyoming by making sure your boat and gear is Drain, Clean, and Dry.


Origin: Asia

Distribution: Throughout the United States. Hydrilla is not known to be present in Wyoming.

Impacts: Clog lakes, out-compete natives, alter water chemistry, reduce fish forage.

Dispersal: Transported as small plant fragments attached to trailered watercraft, or through the aquarium trade.

Characteristics: Heavily branched, small, pointed leaves-5 per whorl. Coarse teeth along leaf margin, midrib often red color, submersed, rooted, perennial.

Additional Hydrilla Information
arrow Hydrilla (Info Sheet)

Hydrilla Hydrilla
Eurasian Watermilfoil

Origin: Europe, Asia

Distribution: Throughout the United States. Eurasian Watermilfoil is not known to be present in Wyoming but is present nearby in Colorado.

Impacts: Displace natives, clog lakes, reduce fish forage and invertebrate abundance.

Dispersal: Transported as small plant fragments attached to trailered watercraft.

Characteristics: Long, branched stems, finely divided leaves, 3-5 per whorl, threadlike leaflets – pairs of 12-20, submerged, perennial.

Additional Eurasian Watermilfoil Information
arrow Eurasion Watermilfoil (Info Sheet)

Eurasian Watermilfoil Eurasian Watermilfoil
Curly Pondweed

Curly pondweed has limited distribution in Wyoming. It was found in Lake DeSmet in 2011. In 2012, it was discovered on the North Platte River between Seminoe Reservoir and Pathfinder Reservoir (an area referred to as the “Miracle Mile”) and also at New Fork Lake.

Origin: Eurasia, Africa and Australia

Distribution: Found in Lake DeSmet, North Platte River (Miracle Mile), and New Fork Lake, Wyoming.

Impacts: Competes with native plants reducing plant diversity and forms dense mats that impact water-based recreation.

Dispersal: Reproduces by seed which can be easily transferred in mud or water. It has been introduced into new areas by accidental introductions and as an ornamental plant.

Characteristics: Leaves are arranged alternately along the stem, and are submersed. The leaf margins are distinctively wavy or 'curled‘ with a prominent red-tinged midvein.

Additional Curly Pondweed Information
arrow Curly Pondweed (Info Sheet)


Didymo (also called “rock snot”) is believed native to the Rocky Mountain area of the United States, including Wyoming. However, it is spreading rapidly throughout the area and is becoming a “nuisance” species. While not considered an AIS because it is native, stopping its spread to other areas to limit the harmful impacts of Didymo is important.

Origin: North America

Distribution: Throughout the United States. Mainly present in western Wyoming.

Impacts: Out-compete natives, impede recreation.

Dispersal: Transported attached to boats and fishing gear.

Characteristics: Freshwater algae, brownish yellow, forms dense colonies or mats.

Didymo Didymo
If you see invasive plants on your boat or equipment or in Wyoming waters, please report it to 1-877-WGFD-AIS or

Wyoming Game & Fish Department Headquarters
5400 Bishop Blvd. Cheyenne, WY 82006
ph: (307) 777-4600
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