Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.
Alisma plantago-aquatica, European water-plantain, is an emergent aquatic plant native to Europe, northern and eastern Africa, much of Asia, and southeastern Australia. The plant is used in the ornamental trade, particularly in northern Europe, and also for medicinal purposes. Both introduction and trade history in the United States is unclear due to taxonomic redescriptions of the genus in the mid-twentieth century that were not consistently adopted by non-taxonomists. The species has become established in several other countries outside the native range, including Brazil, Chile, South Africa, Zimbabwe, Canada, New Zealand, and additional Australian states. It has been introduced through escaping cultivation and is spread by seeds passing through the digestive systems of birds. A. plantago-aquatica is known to be a weed in rice fields, but because very limited information on harm is available from outside the native range, the history of invasiveness is classified as Data Deficient. The climate match to the contiguous United States is high overall, with areas of low to medium match limited to the Sonoran Desert, the Lower Mississippi Basin east into Alabama, and northern New England. The certainty of the assessment is low due to taxonomic confusion and lack of sufficient information on nonnative establishment and impacts. The overall risk assessment category is Uncertain for A. plantago-aquatica in the contiguous United States.
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Uncertain Risk
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