The timing of hedge care directly influences a plant’s health, growth density, and appearance. Trimming focuses on shaping and aesthetics, while pruning involves the calculated removal of material to improve structural integrity and vitality. Performing these cuts at the wrong time can stress the hedge, making it vulnerable to disease and preventing new bud formation. Understanding the hedge’s biological cycle is the first step in determining an effective annual maintenance schedule.
Timing Based on Plant Dormancy
The foundational rule for any significant hedge work is to align it with the plant’s dormant period, typically from late autumn through late winter. During dormancy, the plant’s metabolism slows, and energy is stored securely in the roots. Making structural cuts when the hedge is dormant minimizes physiological stress and prevents excessive sap loss. Trimming during this late winter or very early spring window, before new buds emerge, allows the hedge to heal quickly and use stored energy to fuel vigorous regrowth.
Adjusting the Schedule for Specific Hedge Types
While dormancy is ideal for structural work on most deciduous hedges, many popular varieties require an adjusted schedule based on their distinct growth habits. For example, the timing for evergreen hedges varies significantly depending on whether they are needled or broadleaf varieties.
Evergreens
Coniferous evergreens, such as yew or arborvitae, should be trimmed lightly in late winter or early spring before new growth begins, or after the initial flush of growth in late June or July. Avoid cutting deeply into the old, leafless wood on many conifer species, as they lack the dormant buds needed to regenerate. Broadleaf evergreens like boxwood or holly can tolerate light shaping in the spring or summer after their initial growth spurt.
Flowering Hedges
The most common mistake with flowering hedges is trimming them at a time that removes the buds for the upcoming season. Shrubs that bloom on “old wood,” such as lilacs or forsythia, form buds on the previous year’s growth and must be trimmed immediately after they finish flowering. Trimming these in late winter would remove all spring blooms. Conversely, hedges that flower on “new wood,” like panicle hydrangeas, should be trimmed in the late winter or early spring just before new growth starts.
Timing Considerations for Wildlife and Weather
External factors like wildlife protection and weather conditions place important restrictions on the trimming calendar. Hedges provide vital shelter and nesting sites for birds, and the nesting season typically runs from early spring through late summer (March 1st to August 31st). Disturbing an active nest is prohibited by law in many regions, and this consideration often overrides the ideal time for a major cut. Trimming should also be avoided during periods of extreme heat or drought, as the fresh cuts can cause the plant to lose too much moisture. Furthermore, any significant trimming should stop by late summer to ensure that the subsequent new growth has enough time to harden off before the first hard frost of autumn.
Maintenance Trimming Versus Major Reduction
The intensity of the cut is just as important as the time of year, with different goals requiring different schedules. Routine maintenance trimming is light, frequent shaping intended to maintain the hedge’s aesthetic and size, usually removing no more than 10 to 20 percent of the new growth. This light trimming can occur multiple times from spring through mid-summer to keep a formal hedge tight and neat. Major reduction, often called rejuvenation pruning, involves cutting back into the old, thick wood to significantly reduce the hedge’s size. This severe process causes significant stress and must be performed only during the deep dormancy of late winter, allowing the plant maximum stored energy to recover from such a heavy cut.