The best time to trim a bush (pruning) is not a single date but a specific window determined by the shrub’s type and growth cycle. Proper timing is the most important factor in maintaining plant health and maximizing blooms or foliage. Pruning at the wrong time can accidentally remove the buds that produce flowers for an entire season. Successful trimming depends entirely on understanding if the shrub flowers and when it develops those buds.
Timing for Flowering Shrubs
The most common mistake when trimming flowering shrubs is cutting off the flower buds before they bloom. To avoid this, identify whether a shrub produces flowers on “old wood” or “new wood.” Shrubs that bloom on old wood, such as Lilacs, Rhododendrons, and Hydrangea macrophylla, form buds on the previous year’s growth, typically in late summer or fall. These shrubs must be trimmed immediately after their flowering period concludes, usually in late spring or early summer. Waiting too long risks removing the newly set buds for the following spring’s display.
In contrast, shrubs that bloom on new wood, like Rose of Sharon, Hydrangea paniculata, and many types of Roses, develop their flower buds on growth produced during the current season. These bushes should be pruned during their dormant period, ideally in late winter or very early spring, before new growth begins. Pruning at this time allows the shrub to direct energy into producing vigorous new stems, which generate the season’s flowers later that summer. Cutting these plants back hard during dormancy encourages a more robust shape and prolific flowering.
Timing for Non-Flowering Evergreens and Hedges
For shrubs cultivated primarily for foliage and shape, like Boxwoods, Yews, and formal hedges, timing focuses on managing size and density. Heavy shaping or size reduction is best done during the late winter or early spring dormancy period. This allows the plant to use stored energy to quickly recover and seal pruning wounds before the active growing season. The absence of leaves also makes it easier to see the structure of the branches and make precise cuts.
Lighter maintenance trimming, such as shearing to maintain a formal hedge shape, can be performed two or three times throughout the growing season. The first light trim should happen in late spring after the initial flush of growth, and subsequent trims can occur through early to mid-summer. Stop all general trimming by mid-summer, typically no later than late July. Pruning too late stimulates a final burst of soft, new growth that will not have time to harden before the first severe frost, making the plant highly susceptible to winter damage.
Trimming for Health and Damage Control
Regardless of the plant’s species or time of year, certain pruning actions should be taken immediately upon discovery. This involves removing any wood that is dead, diseased, or damaged. Dead or broken branches, perhaps caused by storms or heavy snow, create entry points for pests and pathogens and should be cut back to healthy wood without delay.
Diseased branches, such as those showing signs of fungal cankers or dieback, must be removed immediately to prevent the infection from spreading. When trimming diseased material, cut at least six to twelve inches into the healthy wood below the visibly affected area. Tools should be disinfected between cuts, and the removed material must be disposed of properly, not added to a compost pile, to stop the cycle of infection.