Floodplains

I was just reading in Reading the Forested Landscape about floodplains.  It says the species found there are silver maple, sycamore, cottonwood, American elm, hackberry, box elder, and ostrich fern.  I often spend time at a floodplain, and those are indeed the species I see there.  The exceptions are 1) I don't particularly recall seeing elm, but it may have been there.  Elm is a tree I recognize, but not a tree that I focus on when I see it.  2) I have been focused on trees, and have not paid attention to ferns, so I don't know if ostrich fern is there. A lot of the area is cultivated, with grass, but I think there is another part that has ferns. 3) There is also a large weeping willow tree in that area.  Perhaps it was not mentioned in the book because it is not naturally occurring in such locations.  It seems plausible that it was planted there, since it is a nice-looking tree.