Each plant species varies in its pruning requirements. In general, the dormant period during winter is commonly regarded as the most suitable time to prune and trim hedges. Removing dead wood and smaller branches does not have a specific optimal timing.
However, if you reside in a temperate area, it is not advisable to trim hedges from early to late autumn. This precaution is necessary because there tends to be a high presence of fungi spores during this time, which can infect and potentially kill the hedges. Ideally, late winter and early spring are the preferred seasons for cutting back overgrown hedges. For maintaining their shape and height, summer is the best time for trims.