What it affectsHydrilla can cause fish kills by decreasing the amount of dissolved oxygen in water. It also outcompetes native plants, which can have negative effects on habitat quality for native fish, invertebrates, and waterfowl and disturb aquatic food webs. Its dense mats can interfere with boating, fishing, and swimming. Dense growth of hydrilla can reduce water flow by as much as 85%, interfering with irrigation canals and other human uses.

What it looks likeHydrilla stems can grow up to 30 feet tall at rates up to one inch per day. They have whorls of 3-10 bright green leaves around the stem and small spines that give it a toothed appearance. It’s generally found at the bottom of 20 or more feet of slow-moving or still water and can sometimes be confused with Elodea canadensis, a native aquatic plant.

Life cycleHydrilla can be either monoecious (individual plants with both male and female flowers) or dioecious (individuals have either male or female flowers but not both). Monoecious hydrilla is the form more likely to occur in northern states. Hydrilla can also reproduce vegetatively by fragments and turions (buds that can form new plants).

Where it’s found and how it spreadsHydrilla is native to Asia and Europe. It has not yet been reported in Minnesota, but has been found in other Great Lakes states, Ohio, New York, and Wisconsin. Hydrilla’s ability to spread rapidly makes it one of the world’s most invasive aquatic plants. It is spread primarily by transport of plant fragments via water currents and recreational boats and trailers. It also produces turions and tubers, structures that can stay viable in the sediment for several years, allowing the plant to regrow even after stems have been removed.

Research at MAISRCBecause hydrilla is not yet present in Minnesota, current research efforts focus on assessing the risk of hydrilla invading Minnesota. This will be based on lab experiments and modeling addressing habitat suitability under current and future climate scenarios. This will clarify our under-standing of risk and guide targeting of early detection efforts.

Learn more at www.maisrc.umn.edu/hydrilla

Learn the facts about hydrilla

Hydrilla (Hydrilla verticillata) is an aquatic plant considered to be one of the most problematic invasive plants in the United States. It outcompetes native plants, serves as a breeding ground for mosquitos, and degrades aquatic habitat. It is found rooted in shallow water up to 25 feet deep, with long stems that can grow up to 30 feet. These stems can grow horizontally on the surface of the water and form thick, dense mats that interfere with recreation.

Photos: Chris Evans, Vic Ramey, Robert Vidéki

Funding for MAISRC is provided by the Environment and Natural Resources Trust Fund, the Clean Water Fund, and private donations.

www.maisrc.umn.edu