Journey with Nature


Hydrilla - known as the "world's worst weed" - has been found lurking in the Hoosier state.

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Hydrilla verticillata is a submerged aquatic plant with heavily branched stems that grow towards the water's surface. It is characterized by its long, slender stems that can grow as tall as 30 feet and are heavily branched with long, whorled leaves. Though usually rooted, it can be found floating in a large mass. Native to Africa, Asia and Australia, it is considered an invasive species in the States.  

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Indiana's first hydrilla sighting was confirmed at Lake Manitou in Rochester of Fulton County in August 2006. This one sighting means that our other lakes and rivers are now more susceptible to invasions of this aquatic nuisance if we don't take the necessary precautions.

Hydrilla is detrimental to our waters because it forms a dense canopy that forces native plant species to compete for nutrients and blocks much needed sunlight to aquatic plants below. Aquatic animals are also affected in heavily infested waters. Fish population imbalances are likely when over abundant amounts of hydrilla is present. Dense mats can raise the water's pH, oxygen levels fluctuate and water temperature rises. The fish are left smaller in size and weight; sportfish populations greatly decline.

Why Should We Be Concerned?

Besides adversely affecting the biodiversity and altering the aquatic ecosystem, hydrilla may greatly interfere with recreational water activities and be a strain on local economies.  

  • Intakes for drinking water, power generation and irrigation can be clogged.
  • Water quality may also degrade due to dense vegetation dying and decomposing.
  • Shoreline access, boating and swimming can be restricted by the thick growth.
  • Shallow water fishing is made impossible.
  • Depresses water-site property values. 

Management of hydrilla is expensive. Millions of dollars are spent each year in herbicides and mechanical harvesters. Unfortunately, the invasive is practically invisible until it's too late; it is only noticeable when it tops off at the surface. The best protection is to prevent hydrilla from reaching our water sources in the first place.

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What We Can Do to Prevent Further Spreading

Introduced by dumping aquarium contents into waterways, hydrilla is now listed by the U.S. government as a Federal Noxious Weed. With this designation, it is illegal to import or sell the plant in the United States although sales made through the internet are possible. Today, the plant travels to new lakes and rivers from plant material on boats, equipment and gear worn in the water. In order to prevent the transportation of hydrilla, please consider these precautions: 

  • Avoid boating through dense hydrilla mats. This will minimize fragmentation and the spreading of plants.
  • Remove all plant fragments from the boat, propeller, and trailer before and after boating. Always dispose plant fragments on the shore.
  • Rinse any mud and debris from equipment and gear before leaving a launch area. Drain any water from the boat before leaving.
  • Do not dump aquarium or water garden plants outside. Seal them in a plastic bag and throw in the trash.
  • Look for Indiana native plants to add in aquariums and water gardens; try Elodea canadensis or Elodea nuttallii