Are You Buying Invasive Water Garden Plants?
May 9, 2007

URBANA - Aquatic invasive species, which have had serious ecological impacts and led to steep economic costs in the Great Lakes region, are probably available right now at a retailer near you. When University of Notre Dame researchers went shopping for invasive species, they found a number of them for sale in the southern Lake Michigan region.

With funding from Illinois-Indiana Sea Grant, David Lodge, biologist, and his graduate student Reuben Keller, set out to assess whether the trades contribute to the introduction and spread of invasive species. They shopped at pet and nursery retailers both large and small, as well as fish markets in Chicago. The researchers found many invasive and potentially invasive species, often misidentified.

“At pet stores, we were able to purchase species that are already invasive, such as rusty crayfish and Asiatic clam,” said Keller. “With these animals, the biggest risk is increasing their spread in local waterways.”

At Asian markets in Chicago, they found bighead carp—often taken home alive. Both bighead and silver carp pose a serious threat to the Great Lakes ecosystem if they become established in Lake Michigan. (The City of Chicago has since outlawed the live sale of both species.)

It was nurseries, however, that provided the richest source of invasive species. “Water gardening poses the greatest risk for new introductions and invasions,” said Keller. “It is a booming business, and shoppers often want the newest and prettiest plants that are hardy for the region. This means that each year there is an influx of new plants that are capable of surviving in the environment.”

Of the plant species for sale, many are already serious invaders in the Great Lakes region, including water chestnut (Trapa natans), yellow flag iris (Iris pseudacorus) and Eurasian watermilfoil (Myriophyllum spicatum). Over the past 40 years, Eurasian watermilfoil has become a serious problem in many local waterways, crowding out native species and interfering with boating, fishing and swimming. In Indiana, for example, it can be found in lakes all over the state, according to Doug Keller (no relation) of the Indiana Department of Natural Resources. "The State of Indiana spends $700,000 a year to control Eurasian watermilfoil and we are barely making a dent in the problem."

The researchers found that roughly a third of the plant species purchased were identified only with common names, which are ambiguous at best. They also purchased 140 plants that were identified with a scientific name, but one-third of those names were wrong.

“We came to the conclusion that most aquatic plants sold in the Great Lakes area are not properly identified, making it impossible for consumers to be sure what they are buying, and difficult for agencies to effectively regulate which species are for sale,” said Lodge.

On the bright side, Keller and Lodge's research results are already informing and inspiring policymakers, natural resource managers and retailers as they address the threat of invasive species. The City of Chicago is voting on an ordinance this week to prohibit the possession of a number of particularly threatening aquatic invasive species. Some plants on the proposed list of 26 species (13 plants, 13 animals) are those that Keller and Lodge found at local nurseries. The researchers worked closely with the Chicago Department of Environment as the ordinance was crafted and will remain on the advisory board to evaluate the species list annually. They are now a part of a new effort in Indiana.

Illinois-Indiana Sea Grant is collaborating with Indiana Department of Natural Resources to organize a working group in Indiana that includes invasive plants experts, along with aquarium, water garden, and other relevant trade representatives. "We are trying to determine which plants pose a worrisome threat and whether they are available in trade," said Doug Keller. "From there we will develop appropriate strategies that may include new regulations or new management practices at stores. Raising awareness is key in this process. The retailers want to know which plants are the 'bad players' so they know not to sell them to the public."

Keller and Lodge's research is published in the May issue of the journal Bioscience. The article is titled "Species Invasions from Commerce in Live Aquatic Organisms: Problems and Possible Solutions."


The Illinois-Indiana Sea Grant College Program is one of 30 National Sea Grant College Programs. Created by Congress in 1966, Sea Grant combines university, government, business and industry expertise to address coastal and Great Lakes needs. Funding is provided by the National Oceanic Atmospheric Administration (NOAA), U.S. Department of Commerce, the University of Illinois at Urbana-Champaign and Purdue University at West Lafayette, Indiana.

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