In message , "keith ;-)"
writes
If you cut them back after flowering on the new wood,then that's
fine.But cut them to half size and you will probably lose them.The
best time to do this is in winter,so they can restart to grow in
spring. He also says in the article : if you see a dead branch it will
eventually
run back into the plant and kill it.

So if you see dead bits, should you cut back to a live bit? Or does it
mean it's had it anyway?

--
Klara, Gatwick basin