New England Wild Flower Society’s Robert Tristram Coffin Sanctuary consists of 177 acres of woodlands, varied wetlands, and a long stretch of shoreline along Merrymeeting Bay, the meeting place of six rivers, including the Androscoggin and the Kennebec. The sanctuary’s most special habitat is the tidal mud flat on the edge of the bay. Tidal currents entering Merrymeeting Bay from the ocean must pass through a narrow, glacial-carved channel called "The Chops". Due to the huge volume of water in the bay, saline water from the ocean rarely flows in, creating a large expanse of fresh tidal river shore habitat with many freshwater tidal plants. Visiting at low time, we walk into the mudflats and observe the rare and unusual flora that inhabits fresh-water tidal marshes. Documented species include wild rice, bulrushes, bayonet rush, and the rare estuary beggarticks (Bidens hyperborea), mudwort (Limosella australis), sessile-fruited arrowhead (Sagittaria rigida), and hooded arrowhead (Sagittaria calycina) among many others. Bring lunch, a hand lens, and be prepared for wet feet.