Re: Philadelphus tree - this is over 30 years old and in last 2 years has stopped leafing and flowering. It got so big (about 5mtrs) all I did was reach as far as I could with shears rather than a proper prune. Should we give up on it or prune all back to the thick trunks or perhaps all the way down to base? Thanks - Any help would be gratefully received as this tree has been so beautiful and fragrant over many years.
A mature Mock Orange should only be pruned by 1/3.
Pruning should follow the blooming period.
Here is an article that will help you.