Large grass or sedge

Large grass or sedge

Observation - Large grass or sedge - UK and Ireland. Description: The specimens shown here are growingon the side of a small brook, but there are many of this plant i

The specimens shown here are growingon the side of a small brook, but there are many of this plant in the flooded woodland, and it will grow in gardens, too (as I've found).
The flowering stems can grow to 6 feet or more in height. It's a vigorous plant.