In spring, the shoots of the Cattail (new growth) are edible, that is the white base of the shoot. Peel off the outer layer. You can eat them raw or cooked (steamed, boiled, sauteed). I like them. They taste mildly like cucumber and were good on a salad.
You can make flour from the rhizomes. You want to find the base of the stalk with your hand and follow it down to the rhizome and pull hard to get them out or use a shovel. I cheated and used a shovel. ;) Knowing me, I'd pull hard and fly back onto my back in the water. lol I'm a bit of a klutz.
This web site gives a recipe for Cattail flower Griddle Cakes. (click here)
are turning to pollen.