Friend or Foe?

[Crystaltips68]

Does anyone know what this is growing on my allotment?

It's some sort of grass, often called cat's tail grass, I don't think it's what you want on an allotment...

Yes, you need to get rid of it.

I think we have it in the garden, it seeds like mad. There were so many seedlings it looked like grass. Cut the heads off before they seed!