Ecological Risk Screening Summary - American Spongeplant (Limnobium spongia) - Uncertain Risk

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.

American Spongeplant, Limnobium spongia, is an aquatic plant that is native to the southeastern United States. It is sometimes a nuisance species within the native range. Kentucky lists the species as threatened and Maryland lists it as endangered. Although some sources report introductions of L. spongia to Connecticut and New York, these disjunctive populations failed to establish, and it is uncertain if they were the result of natural dispersal or anthropomorphic introductions. L. spongia is in trade as an ornamental plant. L. spongia is listed as a noxious weed in California. The history of invasiveness is classified as No Known Nonnative Population. The overall Climate 6 score for the contiguous United States was high, with high matches found throughout the Southeast where it is native, southeastern Midwest, and MidAtlantic regions. The certainty of assessment is low due to uncertain and conflicting information regarding this species’ native and introduced range and taxonomic standing. Conflicting information is largely the result of some sources attributing introduced populations in California of the congener L. laevigatum to L. spongia. However, most sources treat the two as distinct species. The overall risk assessment category is Uncertain.