What is this?!

[ELW85]

A plea for help, please from someone who has absolutely no gardening knowledge whatsoever (as I’m sure will become apparent)!
This weed is growing in our back garden and we thought we’d gotten rid of it last summer, dug up roots, put weed mesh down but it’s back with a vengeance.
Anyone know what it is and how to get rid of it permanently?

TIA!

This is what it looked like before it was removed (behind my little boy)

I’m not really understanding your pictures. The plant on the left is difficult to identify, there are many plants with long oval leaves like that. Could you possibly wait till it flowers? I don’t think it’s a willowherb but the focus isn’t good enough to zoom in.

The other picture is clearly underground runners, but how do they relate to the first picture?

@MereDintofPandiculation the photo on the left shows what it grew back as (all along the garden and in the pond bit) The runners are what we found when we pulled the weed mesh up, so I’m imagining are the roots of the photo on the left.
it doesn’t flower.

Do I see bamboo over the fence in your neighbours garden? Is it baby bamboo?

@Geneticsbunny you know I’d wondered that!! It pokes through the fence from the other side too.

Is this what it would look like @Geneticsbunny ?

If it doesn’t flower it is highly unlikely to be a UK wild flower. It clearly is a flowering plant so the only reason for it not flowering with you is that it’s not in its normal habitat. Unless it’s a late summer flowerer and you’ve never left it that long?

Could you take a close up of the leaf and of the tip of the shoot. That would tell whether it’s a bamboo

Yes, that is bamboo over the fence.

Is it what is in the pot? Looks a bit like a salvia? But the leaves could be swamp milkweed, a perennial sunflower or marsh pepper?

I suspect that the roots are bamboo and that’s why the membrane was put down- a futile attempt to curtail it invading your garden.
The plant in the first picture could be golden rod I think.

Go onto you one of the apps that identify plants?

That is bamboo. Can be incredible Invasive. Only way to get rid is getting your neighbour to get rid of theirs

cant really see the pictures clearly but as your neighbours have bamboo it could well be that, absolute nighmare, my ex neighbours had it and it just kept popping up in my garden, took a lot to keep on top of it

Probably bamboo? Could it also be euphorbia? I am learning through bitter experience that I won't be planting that again….

In the picture with your little boy, the plant in the border behind him does not look like bamboo.

I use an app called ‘picture this’ and it identified your plant as below.

Yes, well that's apps for you, isn't it.

🤣🤣🤣

If it’s Jerusalem artichoke it’s hard to get rid of, you have to fully dig up. On the plus side it’s delicious, especially roasted like potatoes. It’s low glycemic index and slightly nutty flavour. Looks like tiny gingers? Wait till fall. Also by fall they will be tall. Can be 3-7feet I believe. We tried in containers and it didn’t love that.

There are many species of Euphorbia. You can’t damn all of them just because you’ve had a poor experience with one

@MereDintofPandiculation oh do let me know of a well behaved one if you know of one🙏
Wanted big bushy flowers like the one shown and got meh ones like the other picture!
I’m a rubbish gardener 😂

@Toooldforthis36 The one you wanted looks like Euphorbia characias, which is fairly well behaved. I've got E mellifera ("honey-bearer" from the scent of its flowers) which is well behaved but huge (about 12 foot tall). E myrsinites is also reasonably well behaved, but is a prostate one, liking a lot of sun. Poinsettia of course is well behaved, as is E obesa, which looks like a spherical spineless cactus.

Ones to avoid are E cyparissius - very fine leaves, quite a small plant, but runners get everywhere (although easily pulled out, E amygdala and its hybrids, whose runners are not easily pulled out (although it's useful in complete shade).

E griffithsii spreads slowly, but one could forgive anything for those orange-red bracts.

Euphorbia peplus is a small British native whose seedlings can be a bit of a nuisance (annoyingly there's also an E peplis). E lathyrus regularly feature in "what is this" threads - it seeds, but not so much to be a nuisance, so I try to make sure I always have one in the garden.

@MereDintofPandiculation this is brilliant - thank you so much! X

@Toooldforthis36 Those are just the ones I know. There's lots more of them. And prostrate not prostate - having trained dyslexic DH in the name of his cancer, it's difficult to go back to the original