Posted: 23/09/2016 at 00:01
yes oldest wood back to the base....this will also remove several stems, stems that might have flowered too but it will restore regular flowering
look at the wood that did flower ...I know not much...and cut that back to shoots made this summer.
Hard pruning will create lots of wood that will not flower. Philadelphus, apart from the coloured foliage varieties, are ungainly and unattractive bushes when not in flower so more non flowering stems are not welcome Judicious pruning and patience in removing some old wood every year is required