I think it might be that horrid weed grass, a Carex, that pops up unbidden all over the place, and which I now relentlessly pull out while its small because its a so and so to get out once its large. But see what others say...

Carex pendula Bamboo ? Bane of my life especially as i have a large pond at work and they love water. The odd one on it's own by a pond is nice but they spread everywhere !!!!!!

Yea, that's the one - if that's what it is, you'll be stuck with them popping up all over the place now, so keep an eye out for small plants for the next few years.

Thank you. I think it might be on its way as I am getting too old to be bothered with tough weeds/plants in the garden. I'm off to cut those very attractive seed heads off.

Yes carex pendula got rid of this from the garden 3 or 4 years ago and still find the occasional seedling popping up.

Thank you everybody its on its way in the bin tomorrow morning.

Oh dear. I wanted one of these for ages because it is so dainty and will grow in a wet place, and now I have finally got one I find I have to throw it out. I wonder which moisture loving grass would do instead? I saw some lovely ones at Kew but they weren't labelled.

How about Lazula Sylvaticus Steragram. It does not spread around at all. It does grow out the way but not quickly.

The other forms of Carex aren't so bad, Steragram, and like moisture too. I've grown Carex 'evergold' for instance and never found a seedling anywhere.