On 23/07/2016 18:52, Andy Burns wrote:
My nan and mum used to have a plant which I think they called roof
cabbage or maybe chimney cabbage based on where it grew, ìt grew as a
dense mound about the size of a football, I don't know if this is just a
"country name", google image search struggles to find what it really is,
anyone know?

Could it have been a Sempervivum? A colony can form a sort of mounded
humpty shape. It was a country tradition to grow these "house leeks" on
tiled roofs to ward of bad luck and lightning strikes. There were
several clumps of these on an old pan-tiled shed roof at the cottage
next door to where my in-laws lived.