What is taking over my garden
Having been a keen reader of the forum the time has come to ask for advice. I am not a novice gardener but as you will see no expert either.
I moved into my house last year dug over the overgrown front garden. It was mostly lawn with some old perennials I noticed very few weeds. The soil is heavy clay so I laid a thick mulch of compost bought from a local supplier.
This year my plants are doing well but the whole garden has been invaded by the plant shown in my photograph. Not just a few but literally hundreds given it is a small Victorian terrace that is a lot of plants!! I am presuming my digging let loose the monster but what is it?
I did dig them out a few weeks ago but I now have a whole new crop. Has anyone any idea what it is and how best to remove it?
Secondly I was planning to mulch with bark in the next week but presume I should now wait until the "plant" has been eradicated.
Would be grateful for any advice at all.
Many

Posts
Some, but not quite all, look like one of the willowherbs to me.Their seed blows in the wind and could come from anywhere. It's not rosebay willowherb but I can't get any more precise than that
In the sticks near Peterborough
I third it, I have loads of them and the same type of soil. They are easy to dig up and get rid of.
Thanks everyone,really helpful. Reassuring to know I might be winning the battle. Will wait a week or two before mulching to ensure I have them all.
We regularly have masses of it here too, but it's easy to yank out
I live in west central Scotland - not where that photo is...
if you can get a dry day ( ha ha ha ) you can just hoe them off at this time of year.
Def willowherb. We had a similar question recently with same plant in the photo and everyone said willowherb Greenfingers. Easy to get remove and best to get rid of now before it flowers and sets seed again. Mulch afterwards.
rosebay WH is not the only one with more resistant roots. Dig one up and see what's there. Juts a root, no problem.
Long runners spreading out from the root, make sure you get it all out
In the sticks near Peterborough
Ooops. they did seem to be shallow rooted when I pulled them but will look more carefully next time. It was the number of them that worried me, Will wait and ensure the area is clear before mulching.