I moved into a new house last year and inherited a "blank canvas" of a garden. The house is a new build (built on what was previously farmland) and is on the edge of the development with a drainage ditch beyond the back fence. This spring I have noticed a particularly invasive plant cropping up at frightening speed. After lots of research online it appears to be Rosebay Willowherb.
It is spreading into my newly created borders at alarming speed and even popping up in the lawn. I am digging it up almost as fast as it appears, which is pretty much on a daily basis, but it is impossible to remove all the roots (I have clay soil which makes it harder).
Any tips of getting rid of it? The source seems to have originally come from undeveloped land beyond my boundry fence, so I cannot access this area or apply weed killer to land which is not mine. Apart from weeding regularly, what can I do? I am concerned about any possible effects on my home should it come up as far as the house - can it damage brickwork or structures? If I can manage to control it this year, will it return just as bad next year? Help!