I have a very tall mock orange (must be 9-10ft) growing behind a large rhododendren plant. Not sure if I have been pruning it right for years as pruned in spring. The main hub of branches ar now coming from about third of the way up (partly due to less light from rhododendren and my bad pruning). And new spires formed higher up again from errratic pruning perhaps. Growing very well for some reason! Very dense spires and some have a lot of blackfly/ants. So, do I cut ALL the spires back to certain point now or just thin out? Advice would be very welcome.