These weeds are in London, Ontario, and are over 6 feet high. They have very tiny white flowers which quickly set fluffy seeds. They grow very much like goldenrod, but flower earlier. The flowers don't really open noticeably, such as with fleabane type flowers. (I let these ones grow to get an ID. The seeds blow in from a developer's very weedy field behind me, and they're all through my gardens and lawn.) I've checked many sites including government sites, but can't find these.
