Sweetflag (Acorus Calmus) is a wonderful Native Herbaceous plant used in place of the very invasive cattail. This herbal grass is slow growing and sweet scented. Growing up to 4 feet tall it adds a striking view to backyard ponds as well as erosion barrier to natural earth bottom ponds. This plant removes lots of excess nutrients leaving the water clean. Great also for bog areas.  Very winter hardy, native to north America. 

For backyard ponds with liners: 
Plant in loam soil in a wide pot 12 inches wide or more. The top of the pot can be 2 to 10 inches below the waterline.  Rhizome needs to be right at the top of the soil, not buried below. 

For earth bottom ponds plant in shallow water along the edge in the water up to 10 inches below the water line.  Rhizome needs to be right at the top of the soil, not buried below.