Canadian Goldenrod (Solidago canadensis) is highly Invasive In Europe. I’ve spent months of hard graft removing it from my new garden ..
This is how large parts of the garden looked in August before removal. It was months of hard graft to remove the root “carpet” and rhizome clumps. As you can see in image 3, new clumps are still appearing- these can be lifted with a garden fork. Small pieces of rhizome (image 2) will regrow shoots - even young looking shoots may spring from a large rhizome cluster.
Although the flowers are impressive and loved by bees, the reason it is so dangerous is how easily it can outcompete native species and completely colonise areas. The beds that contained goldenrod were almost 100% only golderod roots and runners. Uncovered beds are now regrowing dormant ornamental perennials which were completely smothered.
However, for the most part complete removal of the roots and the chunky rhizome with forks, spades and mattocks/pick axes seems to control
it well enough. It is however back breaking and time consuming work. Regular checks for new shoots to identify missing pieces of rhizome are needed.
Hopefully within a year or two we will have it under control.