Yes, this one is a thug in the Chicago area as well. A cultivar with double the normal number of petals/sepals appears to be the only safe one to grow (dysfunctional anthers and stigma). We removed all Iris pseudacorus germplasm from the collections 3 years ago and still find plants along our shorelines from apparently 2 sources; nursery grown plants sold "in the green" or as dormant pots under the name Iris virginica var. shrevei and from seeds floating down the Skokie River. Boyce Tankersley Director of Living Plant Documentation Chicago Botanic Garden 1000 Lake Cook Road Glencoe, IL 60022 tel: 847-835-6841 fax: 847-835-1635 email: email@example.com "Not only does Iris pseudacorus disperse by freshwater, it is also at least moderately saltwater tolerant. In my area, it comes down the Columbia River and out to the ocean beaches, along the beaches, where we find seed pods and seeds regularly."