I think it might be Carex pendula, a prolific seeder so if you like it you will have plenty. if not then dig it out asap.

I agree with Seaburngirl, I left one plant in my garden and now it's popping up all over. It likes wet woodland in the wild, and my garden is the exact opposite, but it's certainly a survivor!

It's a thug and I spend my life pulling seedlings up from a neighbour and it's not even pretty, no offence intended! It also pushes up my brick paved driveway.

I bought this for the pond last year, went rampant in its pot and seeded it in another pot. If you like it keep it, my advice is the same as everyone else's. Ditch it (in the bin) if you don't want it.

Oh lord, I felt a physical sinking sensation when I looked at the pic - yes, its Carex pendula, and yes its a pain in the proverbial. It took us an hour to dig out a mature one two years ago, it had got so big with such a large rootball, and I'm still having to check all the time for seedlings, blasted things pop up everywhere... talk about the gift that keeps on giving...

I dug one out some years ago and pulled out yet another seedling only today...

Snap. Been trying to get rid for 20 years. Never, never, ever let it seed. The seeds stay viable for hundreds of years.

Snap. I've got this thug coming up all over my garden, I keep pulling young seedlings up Grrrr!
All started from a pond plant :o((

I agree with all the above but it is a very graceful addition to my garden. Any seedlings? Just pull em up. It hasn't seeded too prolifically either.

I'm getting seedlings from one in my neighbour's garden - grrrrr

Thanks fellow gardeners, out with the flame thrower as soon as the rain stops.
Rain stopped, flame wand incinerated the flowers and now dug out, filled my wheelbarrow.
Many thanks for info.

If you want something evergreen and grass like that droops over gracefully (though without the grass type flowering heads) check out Phormium varieties...

I've always wanted a flame thrower!

I've had the same problem with it, heaved a sigh of relief when it was dug up. Seedlings came everywhere on a regular basis from then onwards. Then we moved and I thought I was okay. Nope, they still pop up in the plants I brought with me but I hope I've seen the last of them now.

We moved two years ago and I'd dug out the Carex about 3 years before that. Just so you know.

They pop up unbidden anyway, Arbuthnot - birds and wind drop and blow the seed a fair distance. The trick is to recognise them when they're small, easy to get out then. Probably one plant in one garden in a street means everyone else gets seedlings too...