I have several sedums...I experimented the 'chelsea chop' on half the sedums. To date the ones that had the 'chelsea chop' are compact and the flower heads are more upright and the plants don't seem to 'topple' over. The other half are tall and need staking because of the height!! So I'm happy to repeat the chop again next year.
I also 'chelsea chop' my phloxes. They don't look happy!! Not too many flower heads. Should I have done the chop on these? Your opinions greatly welcomed.