These Yellow Flag Irises (iris pseudacorus) are growing in the little drainage pond behind our house. This is a non-native ornamental iris that's escaped cultivation and invaded wetlands all over North America, choking out native plants including the cattails - an important species for many wetland animals. Yellow Flag have been banned in some states, including Massachusetts, because they're so difficult to eradicate once they take hold. But the plants are still widely available to purchase for gardens. Native to Europe, Great Britain, North Africa and the Mediterranean region, these hardy escapees can now be found growing wild throughout most of the US and Canada. They truly are beautiful, though, and brighten up the little frog pond nicely. There's no marshes around here so I don't think there's much threat of spreading, but I'll keep an eye out.