We just moved into our new home 1.5 years ago. These shrubs are cut to the ground in the fall - and grow to these massive sizes in no time. People keep asking me... What are they? They are also the boudoir for some flying bugs in June - where they are covered by these mating annoyances....but gone the rest of the summer. Can you help?
Note that this is not a shrub, shrubs are woody plants with persistent above ground stems. Note also that there is at least one knot-weed species of this type that is a noxious weed in North America. http://www.nwcb.wa.gov/detail.asp?weed=104
Maybe not in your region. First of all, we don't have an accurate ID. We could try to do better here if photos were retaken on a cloudy day showing a bit more with the leaves (profile of a branch and an accurate photo of the colour of a leaf). Or, you could make arrangements to take a sample to the Royal Botanical Gardens in Burlington. Once the ID is firmed up, then a better discussion can occur about weediness / invasiveness. There are _some_ in this group of plants that are weeds in _some_ regions, but action has to start from an accurate ID.
Thank you Daniel. I'd be happy to send a sample - as I'm considering to use this as a huge privacy border/wall (700'+). Would you be able to direct me to their address/person who would be interested in helping with this?
This is their plant ID service page. Since there's a fee involved (unless you're a member), you might want to try here first by posting some additional photographs.