I must admit to not cutting mine back. Once the flowers have dropped I
just go around and snip off the dead bits. Then throughout the summer I
continually weave new growth into parts that are a little sparse.
Year after year more flowers have been produced.


Adrian Jones wrote:
I did. Last year I cut it right back after it had finished flowering, cut
it hard down almost to the base. It put on tremendous growth last summer
and I was looking forward to masses of flowers but, frustratingly, only got
six flowers. Perhaps next year will be better?