by Alisha Davidson, Ph.D.
ML&SA Research and Development Coordinator
Figure 1. European water-clover floating on water surface. Photo by Krzysztof Ziarnek, Kenraiz via Wikimedia Commons
The Michigan Department of Environmental Quality (DEQ) Water Resources Division and Department of Natural Resources (DNR) Wildlife Division are working together to better understand the distribution of European water-clover, its impacts, and possible management options. In particular, they are trying to pinpoint the locations of European water-clover around Michigan. European water-clover (Marsilea quadrifolia) is an invasive aquatic plant that still has limited distribution in Michigan. Currently, European water-clover is only found in the Huron River and Clinton River watersheds. The DEQ and DNR recognize that local groups and individuals who have ‘eyes and ears on the ground’ may have valuable information to contribute regarding distribution of this species. Knowing its distribution will assist state agencies in management efforts to hopefully stop further spread. As those of us familiar with inland lakes know – once a species is established and widespread, eradication is nearly impossible. Preventing the introduction and spread of species is the best option. European water-clover has the ability to form dense, mono-specific stands by out-competing native aquatic species. Its ability to adjust the angle of floating leaflets to optimize sunlight gives it even more of a competitive edge over native species.
European water-clover is a rooted aquatic plant with floating leaves and is easily identified (see Figures 1 and 2). It typically grows in slow moving waters, like embayments and side channels with silty or sandy substrate in inland lakes and along shorelines or shallow water less than 2 feet deep. Based on recent monitoring efforts, it has been found in the Huron River in Washtenaw County from North Maple Road above the Barton Dam, downstream to the Argo Dam in Ann Arbor. It has been found in the Clinton River in Oakland County, Waterford Township from US-24 (Dixie Hwy) downstream to Cass Lake. As of mid-October, this plant was still green; although, it’s likely getting close to dying off soon.
If you have information on previous or current observations of European water-clover, please share detailed location information with Bill Keiper, keiperw@michigan.gov or 517-284-5553, or report to the Midwest Invasive Species Information Network www.misin.msu.edu. Pictures are also welcome. This information will be used to inform current and future monitoring efforts and the development of a response plan, as appropriate. Please share this request for information with relevant groups or individuals in the Huron River and Clinton River watersheds.
For more information about European water-clover visit:
https://www.michigan.gov/documents/deq/wrd-ais-week-european-waterclover_444413_7.pdf
(Please note that the population in the northern lower peninsula has not been confirmed.)