Keep Hydrilla Out of Michigan

By Emma Costantino, Outreach Coordinator
North Country Cooperative Invasive Species Management Area

When children go swimming in lakes and rivers, they sometimes imagine monsters like swamp thing lurking down below. As people get older, we sometimes learn that the real monsters that threaten our lakes and rivers are us. There are several aquatic invasive plants that would be concerning to find in the Muskegon River Watershed, including hydrilla. Hydrilla has been found in several states in the Eastern U.S., but has not yet been detected in Michigan. If hydrilla did enter the state, it could become a monster of a problem.

Hydrilla is a submerged aquatic plant that can reach 30 feet in length. Its leaves have serrated edges and grow in whorls of four to eight. The midrib, or the central vein of the leaf, can also have serrations on the underside of the leaf, although these are not always present.

The long stems of hydrilla tend to get tangled and form dense mats. Large infestations can prevent light from reaching the bottom of the lake and crowd out native vegetation. This in turn disrupts available habitat for fish and wildlife. Hydrilla also prevents people from being able to recreate in the water because the mats are too dense for swimmers and boats to move through.

Hydrilla is often spread between bodies of water by fragmentation. A few fragments of the plant can create new infestations when transported by unsuspecting boaters. In order to prevent hydrilla from establishing a population in Michigan, it is important for boaters to clean, drain, and dry boats and trailers each time they use them. Early detection is also important as it can help to start control efforts as soon as possible to limit the damage of the invasive plant. To learn how to monitor your lake for hydrilla and other aquatic invasive plants, visit

Emma Costantino is the North Country Cooperative Invasive Species Management Area (NCCISMA) Outreach Coordinator. She can be reached by calling (313) 570-6853 or by emailing

Dense Infestation of Hydrilla. Photo Credit: Leslie J. Mehrhoff, University of Connecticut,


Close Up of Hydrilla.
Photo Credit: Robert Vidéki, Doronicum Kft.,