One can read it everywhere : When to prune shrub X and when to prune Y, but reasons why are not given. Apart from that I will have less blossom/fruit next year, what harm would it do to a shrub when I prune it at another time of the year then is recommended? Thanks. Fons
Shrubs either flower in spring or early summer, having formed their flower buds the previous year or from summer to autumn having formed flower buds the same year.
Those that flower before the end of July can be pruned immediately after flowering while those shrubs that flower after the end of July can be pruned in winter or early spring.
Pruning at the wrong time can disrupt flowering.