Here is the online album I made there is definitely a Conyza canadensis or canadian horse weed /mares tail but there is a different water plant called horse tail and mares tail that is a water plant not to confuse.

variation to leaves texture and color some will flower some just grow taller I been observing for 12 months )

My yard is basically a who who of weeds I got them all !

http://www.facebook.com/home.php?#!/album.php?aid=17038&id=1777040585&ref=mf

Here is a link that might be useful: entire album of my weeds some flowers hiding out to