Cattail flour making is a long process but one that can bring immense satisfaction. Fall is the best time to collect the rhizomes and root stock for making cattail flour as they are rich in starch. My parents have a pond full of cattails in their front yard and it became a family event to collect the leaves to make cattail baskets and the rhizomes to make the flour. The rhizomes are the stems of the cattail that shoot off laterally underneath the plant. They give rise to the new plants and thus are full of nutritious value. When you collect the rhizomes you will see that they have a spongey like quality. This spongey part can be peeled away to reveal the dense starch packed interior. This is the part that you want to get to. When you get to this inner core you will see that it contains a lot of fibers. You can push these fibers in a container of water and they will seperate from the starch. Eventually the starch will fall to the bottom of the container. You can drain this top sludge and dry out the remaining starch in the hot sun or an oven set on the lowest temperatures. The starch will still contain bits of fiber so I put it in a mortar and grind it to get the fine powder I want to use as flour.