Charlie Pridham wrote:

Beware its extremely invasive, but we love it see
www.roselandhouse.co.uk/pond/pond.htm

My neighbour hissed at the thought of them yesterday and warned they'll
travel "even underneath brick walls"! Well, I guess they would. Why
not? They won't travel THROUGH brick walls though.

Funny thing is, in three years here we've only got two of these, six
inches apart. They don't seem to be spreading. Anyway, I've read that
they're easily controlled if you shove a spade deep down around them
twice a year?

Eddy.