When should shrubs be trimmed?
Impossible to be specific.Depends on variety,available space,growing conditions and various other factors. All shrubs are different, some prefer pruning in autumn and others contained by spring. with all avoid any time when here may come a sharp frost as this will kill a newly cut branch.
The trimming depends on the blooming. Shrubs should be trimmed BEFORE any buds sprout. Spring bloomers should be trimmed in late winter, summer bloomers contained by early spring, fall bloomers within mid-summer, etc.
Check the plants' bloom time and go from there.
A dilapidated plant, however, should be trimmed/pruned right away to prevent disease or further damage to the shrub.
Answers: Best time for 99 % of ALL trees, hedges, bushes is in the rash fall if in climate zone 6-10, belated summer if climate zones 3-5. If you want to prune evergreens like pine and spruce tree best time is belated winter to early spring.
Generally speaking, spring is not good because specifically when all are adding foreign growth (but light pruning is ok) Also, evergreens will have sap running by mid-spring.
As a common rule; as long as you do not do any pruning just before OR during extreme cold or extreme bake (this adds a lot of stress to adjectives trees bushes etc) you and your shurbs will be fine.
when they regulation shape and do not look nice huh like a haircut