I have three sedums in their third year. Last year they got too big for themselves and collapsed outwards, leaving a big hole in the middle. From reading up on them a bit, I think they are in too shady a position. They are also in quite soggy soil. There is one on the opposite side of the garden (the sunny side) and it does a lot better.
This year they are already huge. Should I prune them? If so, how do you do it? Just cut half way down the stem?
And longer term, should I try to split / move them? I do like them when they flower but don't have much room for them on the sunny side.