How to Prune common myrtle?
For free-standing plants: Prune lightly as needed to remove unwanted shoots and keep the shrub in shape. Prune in mid- to late spring. For wall-trained specimens: On established wall-trained shrubs, shorten sideshoots to two to four buds from the framework; remove shoots growing towards the wall. Prune annually after flowering on last-year growth, or in late winter or early spring on current-year growth.