Many invasive plants are still being sold at garden centers
Hand-wringing by members of the ultimate invasive species.<p>I went with my son’s middle school class on a field trip to the Audubon Society preserve in Portland, years ago. The guide gave the kids a long lecture about evil English ivy, explaining the concept of non-native invasive species. Portlanders organize groups to tear down the ivy in parks, often trampling the native ferns in their zeal.<p>Not ten minutes later the same guide showed the class a family of ducks crossing the path. Everyone oohed and aahed  — ducklings, so cute. My son pointed out that they were mandarin ducks, a non-native species. The guide went quiet.