Yellow flag iris. This is a Class C noxious weed in Washington. Had I known this before introducing it to my farm pond, I would not have done so. We have tried, unsuccessfully, to eradicate this Pacific NW bully. It both increases from the roots and also self-seeds. It does seem to prefer standing water and will limit itself from the pond edge to about 2' deep. So far, it has not infiltrated the creek.
