I will soon be establishing a new pond in Iowa, Zone 4. Within this pond will be an area for bog plants. Additionally, I want to put bog plants in a filter/waterfall system as the biofilter part. The pond is almost completely shaded, only one edge getting low-angle sun for about two hours in the summer. I'd appreciate your suggestions and warnings about possible shade-loving Zone 4 bog plants. I have tried Arrowhead and some kind of Iris, about 12" tall, with a small yellow flower in the past and they have grown well in wet, shady heavy organic soils.