Pruning climbing roses
 

My climbing rose 'Iceberg' planted just over two years ago is fast becoming
over grown. This year especially it has romped away and been smothered with
magnificent flowers right from early spring. Now it has almost stopped
flowering but is still producing new growth that has covered the large
trellis area supporting it. It now needs a good prune and thinning out of
old branches, but when is the best time to do the prickly job? I have had
conflicting advice, now after flowering, or wait until early winter. Also,
how much old growth should I leave? Any expert advice from group members
would be most welcome.

Thanks,
MikeCT