Flowering Cattail. Tail shaped male flower at top, female flower below on spike.

Cattail and poisonous Flag grow in a similar habitat and the young plants are easily confused when not in flower.
The bluish, fleshy Cattail leaves fan out from the more compact base and have a rounded profile and a whitish bloom on the surface.
Flag leaves are flatter, shinier, brighter green, and have a distinct ridge along the center of the leaf blade.