Flowering rush (Butomus umbellatus) is an invasive plant of riparian areas. It is a native of Africa, Asia and Eurasia and was first detected in Laprairie on the St. Lawrence River in 1905.
This plant was brought to the US intentionally as a garden species. It is difficult to control and should not be used in the garden to prevent further spread.
For more information about this plant pest, see the CABI data sheet.