Sorry. We spent 20 years failing to get rid of it in our last garden. Hope you are more successful.
Roundup on every leaf every time you see one is probably the best idea I can offer. Every day if need be.

WOW,,,perhaps it should carry a warning !!!

You are not alone. I thought that I knew a little bit about gardening but have fallen foul of the Japanese Anemone. I have tried digging it out but as OB suggests the way forward will be painting the leaves with Glyphosate and a lot of patience.

Do you know someone that could move the rock for you and then dig them out, if so dig deep they do have long roots, it’s hard to visualise the situation but assuming the rock is far to big to move and they are coming from under the side then this is what I would do and it normally works really well, dig down a little under rock, then slice into the root , the further down the better and then dab on using Colton wool bud some neat Diesel,don’t pour it on, you could dab on some sbk but a dab of diesel always works for me especially on perennial weeds like docks dandelion and thistle between paving slabs etc.

Diesel...now that's interesting worth a try. I cannot move the rock its been there too long and is far too big. But the diesel is easily come by...will give that a go. Thanks for your kind attention.

Just remember when severing the roots that they grow from root cuttings so you may be compounding the problem.

Gosh...Japanese Anemone is not a pseudonym for Knot weed is it?
Any roots would be on the bonfire tout suite !!!

I'm glad I read this question because I was thinking about adding some Japanese Anemone to the car park border I'm volunteering tending

This reminded has me off it's wayward tendencies and I shall pass on that idea

I'm pleased I reminded you as you...such a pity as it is a very pretty plant...but also a bully !!

I'm having the same problem with a particular orange day lily. It's growing up through concrete! I just yank it out whenever I see one or mow it down. Digging it out is the only way to really get rid of it.

What is really annoying is that some people post that in their garden Japanese anemones are well behaved. I have a feeling that some of them are, certainly the white ones seem to be less thuggish.

Didn't know there were white ones. To continue the theme of thugs what about Grape Hyacinths. OH BOY do they take off if you use a fork around them off go the little bulblets and they are all over the place. Leave them alone and they are OK. Oh well thanks for all the info. Keep safe.

Ah, it was the white ones I had in mind for the car park border, maybe pencil them back in now?

I suppose if the car park border gets trodden down and generally abused the solution sounds like Japanese anemones under planted with Grape Hyacinths :-)

There are white Grape hyacinths as well, could become a tough as old boots white border

However the world being what it is they would probably just die if you actually wanted them to thrive

I might try the diesel thing. They send stems up throug my gravel path and if you pull one it's root can be a foot long but you still didn't get it all. I've been fighting this battle for years yet my sister has a clump which has never changed and has never spread. I could say worse about Golden Dead Nettle / Lamium galeobdolon and Vinca major, white and blue. Thugs of the first degree!

I once planted a root of Japanese anemone in a sunken bucket in the border so it would not spread...but it died...its as if it needs to spread Grrrrrr.
Well Thank You all for your kind attention. Keep Safe and Best Regards

Have you tried Honorine Jobert? That's a pretty white one and in my garden it was very well behaved(which is more than can be said for the pink one...

No I haven't but will have a look as it is a lovely border plant...but certainly not the pink one. Thanks

Can I just also say... Julien's tip about diesel do as he suggests use a cotton bud to just dab onto the root. If diesel is tipped on the soil it will contaminate for ever.
Thanks again for your interest.

I have several different ones and the only real thug is Queen Charlotte, but it took 4 yrs of sulking before finding its feet so to speak. I do wonder if the fact they are in partial shade and poorish soil is the reason for their behaviour.

I've only got a small clump (put in last year) and debated whether or not to remove them. Having read all the comments I am definitely going to do so now!

Isn't it a pity...because the flowers are pretty and they do fill a spot if only they would not spread so much so quickly. What I also dislike is the way the foliage seem to go paper dry and wilt while the flowers are at their best. Oh well I shall keep zapping them until they give up or I do...battle of wills.