The objectives of pruning shrubs are to maintain vigor, remove damaged or diseased branches, help maintain the natural size and shape of a plant, and improve flowering and fruiting. There are four basic pruning techniques used for maintaining shrubs: heading back, renewal, rejuvenation, and shearing. For information on pruning specific shrubs Pruning deciduous shrubs by species.pdf
TIME TO PRUNE
A general rule-of-thumb is that shrubs that bear flower buds on the previous year’s growth should be pruned after spring flowering. Some examples are forsythia, mockorange, and lilac. Shrubs that bloom on the current year’s wood should be pruned in early spring before bud break. Among these are St. John’s wort, cinquefoil, and snowberry. This rule does not apply when doing rejuvenation pruning.
Some old, neglected shrubs can be restored to vigor by pruning all stems or canes to ground level. Among those that respond well to this treatment are: forsythia, weigela, privet, honeysuckle, spirea, and hydrangea. Rejuvenation pruning is best done in late winter or early spring.