This story originally appeared on the Illinois Natural History Survey website.

When clearing out the foliage from an aquarium or backyard water garden this fall, keep water hyacinth and other invasive plants out of streams, rivers, and other waterways.

Water hyacinth has been described as “the world’s worst aquatic weed,” lovely in the garden, but a nuisance in the river, according to Andy Casper, director of the Illinois River Biological Station of the Illinois Natural History Survey (INHS), Prairie Research Institute, University of Illinois.  At this time of year, the plant can be spread easily.

“Water hyacinth is the aquatic version of kudzu,” Casper said.  “It grows faster than any other plant competing with it, quickly taking over a pond or river-bed.”

As the plant spreads out over a water surface, it blocks the sun, so native plants can’t survive.  Fish that once hid amongst the underwater plants to hunt for their prey and young fish that hide from predators experience a changed habitat.

Additionally, in the fall as the water hyacinth dies, it sinks to the river bottom, decomposes, taking the oxygen out of the water in the process.  Too little oxygen can lead to large fish kills in the winter when oxygen is naturally in short supply.

Deliberately dumping water hyacinth plants in the waterways will cause the plant to spread, as well as composting plants too close to a river, stream, or drainage ditch. Backyard flooding can also cause the invasive plant to spread into nearby surface water areas.

In one case in which plants spread, an individual composted water hyacinth plants on a pile at the edge of a yard located close to the river.  The result was a big pile of water hyacinth down river, Casper said.

“All it takes is one good growing season, and the plants take over,” he said.

In a survey of the entire Illinois River from Hennepin, Illinois to Joliet, Illinois by airplane and boat, INHS staff discovered 15 individual water hyacinth beds in the river. In addition, fish surveys also showed that whole water hyacinth seeds were present in the digestive tracts of carp, indicating a threat of dispersal of the seeds to other areas. Seeds were present in 27 percent of the digestive tracts of the common carp examined, regardless of their proximity to water hyacinth beds.

For proper disposal of water hyacinth, place plants in a plastic garbage bag and throw them away. Keep all plant parts away from waterbodies because the seeds are tiny and can be missed by the naked eye.

Water hyacinth is an economically important plant for the water gardening industry.  For this reason, the sale of water hyacinth has not yet been prohibited by the State of Illinois, as the debate continues on whether it survives a cold winter, according to Pat Charlebois, INHS aquatic ecologist.  Many states, and the City of Chicago have prohibited the sale of this plant.

Water hyacinth is just one of many invasive aquatic plants that should not be discarded in waterways.  Hydrilla, a formerly common aquarium plant, is another plant that carries a financial toll when it spreads uncontrolled.  Plants such as these clog waterways, impeding boat navigation.  With government cleanup, millions of dollars may be spent, and recreational areas may be closed, reducing recreation-based incomes.

“Hydrilla is such an aggressive plant and spreads so quickly that it can take years to completely remove it in lakes and rivers,” Charlebois said.  “Because of this, the State of Illinois has an early detection and rapid response plan in place in case hydrilla shows up in an area.”

Charlebois and colleague Greg Hitzroth, INHS outreach specialist, are seeking to change the behavior of people who purchase and use plants for outdoor water gardens and indoor aquariums, encouraging them to dispose of all aquatic plants in sealed plastic bags in the trash.  Consumers can find a list of Illinois’ invasive plants at TakeAim.org. The State of Illinois regulates some plants, but others, which are not regulated, can be just as much of a nuisance.

Consumers often look to retailers for advice on which plants to purchase and how to care for and dispose of them.

“We partner with retailers, educating them not only on which species should not be sold, but also giving them alternatives,” Hitzroth said.  “We have had success with this effort because most retailers want to do the right thing.”

There’s a loophole in these efforts, though.

“A huge market for aquatic plants is offered for sale online, which can be difficult to regulate,” Charlebois said.  “This is a sticky wicket because retailers in another state may not know which plants cannot be sold or shipped to customers in Illinois.”

Charlebois and Hitzroth have been working with wholesalers, retailers, scientists, hobbyists, consumers, and others and attending hobbyists’ tradeshows to create outreach material that aims to prevent the spread of aquatic invaders in trade.

They also worked on a statewide campaign about invasive species.  Part of that effort is the Release Zero campaign, which aims to provide suggested alternatives to release plants based on published guidelines for teachers and water garden hobbyists from the Aquatic Nuisance Species Task Force.

More information about aquatic invaders in the market place (AIM) can be found at TakeAIM.org. Alternatives to the release of aquatics in trade can be found at ReleaseZero.org.

Not all non-native plants and animals turn out to be invasive in a new environment. How can we predict whether a species poses a threat to local waters? If we could predict that, how can we make the best use of that information?

IISG and University of Notre Dame researchers set out to answer the first question by analyzing which traits help a species thrive in a new environment. They brought this data to an Indiana working group looking to proactively prevent the introduction of invasive plant species through water garden and aquarium retailing. The group of researchers, resource managers, retailers, and hobbyists created a risk assessment tool and their work led to 28 aquatic plants being banned in the state.

As a result of this work, Notre Dame’s David Lodge, and Reuben Keller, now with Loyola University Chicago, were funded through the Great Lakes Restoration Initiative to create risk assessment tools for all taxa in the Great Lakes, including crayfish, fish, mollusks, plants, and turtles. These tools can help decision makers establish consistent and comprehensive regulations focused on species that pose the biggest threat.

Meanwhile, IISG’s aquatic invasive species (AIS) team has been pulling out all the stops to distribute information that can help prevent the spread of AIS in trade—in other words, species that are bought and sold for water gardens, aquariums, and to a lesser extent, classrooms. Leading the effort as part of the Great Lakes Sea Grant Network, and informed by social science research from North Carolina State University, the specialists are targeting all levels of this AIS pathway—from retailers to hobbyists—and sharing information across the region through a variety of media.

The suite of tools contains publications for retailers and their customers that include lists of non-invaders as well as known or potential invaders. “Many of these resources are informed directly from the risk assessment findings,” said Pat Charlebois, AIS outreach coordinator.

Great Lakes Sea Grant programs and the Sea Grant Law Center are contributing their expertise. For example, Wisconsin Sea Grant created a training video for water garden retailers, and Ohio Sea Grant hosted a webinar for aquarium hobbyists. In addition to writing news articles, other programs helped craft non-technical versions of relevant state regulations to give retailers easy access to the information.

All of this work is raising awareness and potentially changing behavior. “Most of the retailers that have received materials about the risk of AIS have reported that they will distribute publications and talk with their customers about invasive species, and a majority will avoid selling them,” said Greg Hitzroth, IISG AIS outreach specialist.

You can find these resources and many more on the new website Aquatic Invaders in the Marketplace (AIM) or TakeAIM.org. AIM are aquatic plants and animals available for sale that can negatively impact ecosystems, economies, or public health. These organisms are commonly found in the live food, aquarium, pet, biological supply, live bait, water garden, and aquaculture industries.

This comprehensive resource provides a wealth of information for resource managers, retailers, hobbyists, aquatic farmers, and more on how to prevent the spread of AIS that can happen with plants and animals that come to new environments through the marketplace. The website includes links to regulations, lists of contacts and invasive species, and species prediction tools for the Great Lakes and beyond.

Illinois-Indiana Sea Grant is a part of University of Illinois Extension.

With the peak of summer right around the corner and gardening season in full swing, we’d like to use this moment as a reminder to be careful about what you choose to plant – particularly if you have a water garden.

A departure from traditional dirt landscaping, water gardens come with their own set of complications and challenges when it comes to the spread of invasive species. Some key things to keep in mind – make sure your water garden is not near any waterways or flood-prone areas to reduce the risk of any species spreading to natural areas, and always rinse off any dirt or debris from all parts of the plant before planting, to get rid of any potential eggs, animals, or unwanted plant parts and seeds.

If you are planning on cultivating a water garden this summer, and would like more information, check out our brochure and handy wallet card  for tips and guidelines on what precautions to take during the gardening process, as well as lists of what plants to grow and what plants to avoid.

These lists are the product of research conducted at Loyola University Chicago and University of Notre Dame, taking into account biological characteristics such as rates of reproduction and climate tolerance to determine which plants are most likely to become invasive. On the flip side, horticulturists and scientists from the Chicago Botanic Garden were consulted to figure out what native or non-invasive plants are the best alternatives. With this information, we hope you are successful in making your water gardens a little safer, and your summer a little more beautiful.

For more information on invasive species and what you can do to help, visit TakeAIM.org.

Illinois-Indiana Sea Grant is a part of University of Illinois Extension.