Calamus, or sweet flag, growing by the water.
sweet flag definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a perennial marsh plant (Acorus calamus) of the arum family, with sword-shaped leaves, small, green flowers, and a sweet-scented rhizome
sweet flag definition by American Heritage Dictionary
A hardy perennial herb (Acorus calamus) of the Northern Hemisphere, growing in marshy places and having grasslike leaves, minute greenish flowers borne on a thick spadix, and aromatic rhizomes. Also called calamus.