In our area (around Washington DC), the goldenrod/aster flow in the Fall is
normally left for the bees as winter feed.  The flow itself runs roughly from
mid-September to mid-October, and is quite variable in intensity (1997 looks
like a good year for it here).
 
Even though I don't harvest goldenrod/aster, I have tasted the honey and
consider it to be acceptable.
 
W. G. Miller
Gaithersburg, MD