Thank you for your question. It doesn't appear to be on the list of invasive species for Michigan. As for identification, if you could send some pictures from some different angles as well as a leaf or two (back and front) with a measurement reference, it would be helpful. Are there any flowers or old fruit ? It would also help if you could describe the location (e.g ten feet from water, in water, etc)as well as other flora in the area.
I look forward to hearing back,
After looking at this further, I have some additional questions. Does this plant appear vinelike or erect? Are the leaves arranged directly opposite each other or do they alternate on the stem?
I look forward to your answer,
I looked further in the pond just up from the creek and found another plant in the water. I have a picture and it looks like a ground cover in water very thick all across the water. Also another picture of the first plant I asked about, which is upright, no flowers, leaves are across from each other. And the ground cover plant has an occasional yellow flower.
Thank you for the pictures. The second plant you presented appears to be watercress (nasturtium officinale). What is concerning is that the flowers are white. Although invasive removing it may not be desired. See the following link:.
I am still trying to identify the first plant. I really need to see the individual leaf shape and would like to know if the leaves come out opposite each other on the stem. I will be forwarding the pictures to MSU to see if someone recognizes the plant.