It's certainly not leonotis.
The manner of growth suggest one of the annual polygonums but that's not a definite ID
The prunus seems a likely suspect. It's what they do.
I haven't found a wayof stopping them. I have this prunus, (or similar), alder and wild cherry suckering in various places in the garden.
Yes, thug, I didn't think to mention that. Herb Robert very similar but easier to remove
Unless it affects the meaning it's not worth worrying about. I'm a lousy typist and mine often go through with errors
I think you have Geranium robertianum and Geum urbanum there.
That's herb robert and wood avens
Suckers don't always look the same as the tree if the tree has been grafted onto a different rootstock. Can you get a clearer photo and a photo of the base?
It's on a lot of the bee plant lists but I've never noticed it attracting many
Digging it up might be tricky. Looks like a tree sucker to me
They have the look of tree suckers