Sandman, in response to your question about the invasiveness of yellow water iris: my experience of probably 18 years with yellow water iris is that it does not invade out into the lake to a significant degree. What it does do is claim shoreline by spreading laterally. It has been pretty slow to cause problems at my place although we have had to spray glyphosate a couple of times where it took over. It outcompetes some of the plants I prefer as marginals such as pickerel rush, thalia (American water canna) and Louisiana swamp iris (I have a big stand of Black Gamecock that it tries to invade). On the good side it stabilizes shoreline like a concrete wall so I have it planted where the Oklahoma winds try to erode my shore. The mature root system is like a network of interlocking 2"x4"s.
