By Lexy
United Kingdom 
Hi,we have this beautiful bush/shrub in our garden. Over the past 10/15 years I've cut it back in October and the following years the growth is minimal to sparse. There's also a clematis ( Montana ) growing on it. Last year I didn't trim it and we've been rewarded by spectacular blooms. Ok....so first up...what kind of bush/shrub is it ? Secondly, when should I trim it ?
12 Jul, 2016
Answers
Could be Viburnum of some kind but close up would help.
12 Jul, 2016
I would guess at Philadelphus 'Virginal'. If it is then after flowering.
12 Jul, 2016
Could be a Philadelphus, but possibly not P. Virginal, which is quite a compact variety (in my experience, at least).
Philadelphus should be pruned immediately after flowering. Any later, and, as you've discovered, you'll be chopping off next year's flowering stems.
If it is a Philadelphus, I'm surprised you're growing C. Montana with it. The Montanas are vigorous, and it will eventually swamp the Philadelphus and kill it. Better, I would have thought, to grow one of the Clems in pruning group 3, such as a Viticella.
12 Jul, 2016
Philadelphus 'virginal' gets my vote (it can easily make 10 feet) but a close up would help to be sure.
12 Jul, 2016
If you can catch the scent before you reach the shrub, it's Philadelphus!
12 Jul, 2016
Can you show a close-up photo of the flowers and leaves? thanks
12 Jul, 2016