I've got a horrible feeling its that weed which flowers yellow - hard to say, pic's too far away for detail of leaf, and the one I'm thinking of has a tendency to mimic plants you want - when they're small, could be mistaken for a Geum that you do want, like Mrs. Bradshaw for instance, or G. rivale. I think its a weed form of Geum, in fact, Geum urbanum or wood avens, but am not 100% sure. It wouldn't be surprising if you had loads of them - let one remain one year and you'll have 20 the next...

Its very similar to my Japanese anemonies but you won't know unless you let it flower.

Yep, it is also similar to Japanese anemone. If its those, they don't flower till early autumn, sometimes late summer. If its the weed plant I mentioned, they flower earlier.

Thanks. I've just tried to upload a closer picture of the leaves too.

Ah - looks very much like Japanese Anemone and not the tedious weed!

yes I agree its Jap anemone. can be invasive if its happy but easy enough to keep in check.

Thanks for your help, I definitely prefer the sound of the anemone to the weed! I'll cut back last year's stalks and see what it comes up with this year.

Seaburngirl is being a little conservative. It is one of the most impossible to get rid of plants in the world. I have a patch which has been dug out and then weed killed for the last 8 years with Sodium chlorate and it is still growing! Nothing else has managed to survive in that bit of land, not even Dandelions.

But they're very useful space fillers in dark places and mine flower from July to October. I wouldn't be without them.

They would be useful plants for dark places, if they stopped there, but the ones in our garden (not planted by me) have spread so far that they kill off every other plant in their vicinity and move out into the paths and even the lawns. Oh and if not dead headed, they seed all over the place too and the seedlings if allowed to flower are tiny squinny flowered monstrosities.

I get the impression you're not too keen on them, Owdboggy! ;-)

I've got two plants, different shades of pink and they haven't yet taken over the garden in 10 years. Perhaps my soil is naff!!

I hate them almost as much as I hate Roses!.

must say that mine have not been the thugs reported [almost sad] they have been in for 10 yrs and from a 2lt pot full it now covers 1m x 0.5 m patch. I think it depends on the variety.

Lucky. On at least another 2 garden sites I visit, it is one of the most asked questions, how to get rid of the thug. The white version Honorine de Joubert (or something like that) is a reasonably well behaved version.

These ones don't seem too have spread out too much yet, though I've no idea how long they've been there. I'll have to wait and see what type they are once they flower. Any tips on how best to keep them in check?

dig out the young growth so you can see where they are appearing.