Can anyone tell me what this is please, it spreads like wild fire and has even grown between the red bricks on the patio
It could be Sweet Alyssum, Lobularia Maritima.
I think it looks like a sort of grass. We have a short, thickish leaved grass that may have been something a previous owner planted, but it is a pain in the neck, pops up everywhere, in the lawn too. I've pulled a lot out and it comes back, but I don't know what it is.
Dordogne and Norfolk
Do you have any Carex pendula (Pendulous Sedge) plants nearby? It looks exactly like the seedlings I get from the huge ones growing down the side of a stream (ditch...!) that borders our garden. It's my first year here, and I've already found that despite regularly clearing the seedlings, more seem to spring up as soon as my back is turned.
I'm inclined to agree with Anna33. We have one in our garden. I hate it and my wife loves it but it is quite a thug that I have to keep an eye on to keep it under control.