Pruning evergreens requires precise timing because, unlike deciduous plants, most lack dormant buds on old wood that would allow them to regenerate after a severe cut. Evergreens retain their foliage year-round, making them vulnerable to pruning mistakes. Understanding the natural growth cycle of a specific evergreen is important to ensure the plant’s health and ability to survive the winter. The correct pruning schedule prevents permanent damage and directs the plant’s energy toward desired growth or flower production.
Timing for Needled Evergreens
Needled evergreens, such as spruces, firs, junipers, and arborvitae, have distinct pruning requirements. For most varieties, pruning should be confined to the newest growth, as cutting back into older, bare wood will not stimulate new foliage and can leave permanent dead patches. The timing for these species is typically late winter or early spring, just before the new growth cycle begins, allowing the plant to quickly conceal the cuts. For spruces and firs, pruning can also be done in early summer after the new growth has slightly matured.
Pines are a notable exception and require a technique known as “candling.” Pine trees produce new, upright shoots in the spring called “candles,” which are soft, light-colored extensions of the new growth. To control size and promote denser branching, these candles should be pinched or cut by hand, removing about one-third to one-half of their length. This must be done in late spring or early summer, after the candles have fully elongated but before they harden.
Junipers and arborvitae tolerate light shaping and shearing in early spring or mid-summer. They should not be cut back past the green foliage layer, as the older, interior wood lacks the necessary latent buds to produce new growth. The Yew is the exception among needled evergreens, as it possesses dormant buds on older wood and can be cut back severely for rejuvenation.
Timing for Broadleaf Evergreens
Broadleaf evergreens like holly, boxwood, rhododendron, and laurel are more forgiving than conifers, as many possess latent buds along their stems that can sprout after heavy pruning. The optimal pruning time is determined by whether they are grown for their foliage or their flowers. For non-flowering varieties like boxwood and holly, pruning is best performed in late winter to early spring before the new growth flush begins.
Flowering Varieties
Flowering broadleaf evergreens, such as rhododendrons and azaleas, require a different approach to ensure a display of blooms. These species typically set their flower buds for the following year shortly after the current season’s flowers fade. Therefore, any light pruning or deadheading should occur immediately after flowering is complete, generally from May to mid-June. Pruning later in the season risks removing the developing flower buds, sacrificing the next spring’s bloom.
Size Reduction
If a broadleaf evergreen requires significant size reduction, the pruning should still be completed in late winter. This is the period when the plant’s resources are concentrated in the roots and the risk of disease is lowest.
Structural Pruning and Rejuvenation Timing
Structural pruning involves significant cuts to reduce a plant’s size, correct poor form, or rejuvenate a neglected specimen. This intensive work requires the plant to be completely dormant to minimize stress and the loss of stored energy. The best window is late winter, typically from February through March, before the buds begin to swell and active growth starts. This timing minimizes sap flow and allows the cuts to begin healing with the first flush of spring growth. Furthermore, dormant pruning provides an unobstructed view of the plant’s framework, making it easier to identify and remove structurally unsound branches.
Why Late Season Pruning is Dangerous
Pruning in late summer or early fall, generally from mid-August through October, presents a significant risk to the plant’s winter survival. A pruning cut stimulates a localized flush of new growth, which is tender and full of water. This new growth does not have sufficient time to complete the “hardening off” process—where the plant prepares its tissues for cold weather—before the first frost arrives. Consequently, the water-filled cells in the tender new shoots freeze, rupture, and die, resulting in severe dieback and browning, often referred to as winter burn. This cold-damaged tissue also provides an easy entry point for disease pathogens and pests.