VV - I can't believe it. Check out this link, 6th photo down. http://ontariowildflowers.com/main/species.php?id=528 What was the giveaway? Alternate leaves? You deserve some chocolate truffles, even if you got lucky while yanking my chain. It may well be Prenanthes altissima, but I'll leave this up a while to see if there are any added comments.
Well, the mystery plant has bloomed and illustrated the point that relying on foliage alone for an ID can lead one astray. It definately is NOT a Prenanthes and Viburnum Valley has to give back the chocolate truffles unless he can redeem himself.