What Month Do I Shape My Boxwood Trees?

Despite their association with precise pruning, boxwood (Buxus spp.) are remarkably forgiving when it comes to general shaping. The window of opportunity for reducing the size of boxwoods or pruning dwarf boxwoods isn't restricted to one specific month in Mediterranean climates, but a quick trim allows greater leeway than more extreme plans.

Hardy from U.S. Department of Agriculture plant hardiness zone 4 through 9, depending on the variety, boxwood plants respond exceptionally well to even extensive pruning.

Whether clipped into formal geometric shapes or encouraged to look soft and natural, boxwood rely on appropriate pruning for health as well as form. Understanding the process helps assure your success with boxwood. Some boxwood varieties grow fairly tall, but boxwood are shrubs rather than trees.

Thinking it Through

They can be kept as short specimens and topiary or allowed to grow into a wall-like hedge. Regardless of their shape or species, their pruning response is the basically the same.

Pruning during their active growing season elicits a push of new growth. Plant reserves, redirected from recently pruned tips, rush to latent buds waiting for fuel. That activity stimulates new branching, fresh foliage and a dense canopy.

Timing Labor Right

Even in mild-winter gardens, evergreen boxwood go through winter dormancy, followed by renewed spring growth. Proper pruning balances that growth cycle with unpredictable spring and fall weather common in Mediterranean climates.

If a general quick shaping is desired, trim anytime from late winter through summer. This is the best time to trim boxwoods.

Limit extensive pruning to winter months, when boxwood is fully dormant. Late-fall pruning inhibits dormancy and reduces the plants' cold-hardiness. Heavy pruning in fickle spring weather puts vulnerable new growth at risk during sudden cold snaps. Winter pruning, however, supports dormancy while preparing your boxwood for a burst of spring growth.

Tackling the Job Properly

Some boxwood aficionados promote a pruning technique known as plucking, wherein boxwood stems are broken off by hand. Although the method may seem organic, the ragged breaks left behind invite problems. Boxwood often play host to fungal diseases caused by lax or improper maintenance. Sharp handheld pruners leave crisp clean cuts that heal quickly. When pruning, wear gloves, a long-sleeved shirt or jacket and protective eye-wear, and sterilize pruning shears with a household disinfectant before and after pruning each plant to prevent the spread of plant disease. Look beyond a boxwood's shape to its underlying health, and prune with both goals in mind.

Trimming Boxwoods Way Back

Because boxwood responds vigorously to pruning, shaping that focuses on only the exterior creates such density that sunlight can't reach the interior. Leaves form at the branch tips, and leafless stems remain beneath. Annual winter thinning allows air and light to penetrate and stimulate interior growth. Select branches evenly, throughout the dense facade, and prune back about 6 inches. These openings permit light and air to reach buds waiting inside. If you want formal hedges, then prune boxwood narrower at the top than the bottom, and allow gradual widening to the bottom. That shape ensures even the bottommost branches receive sunlight for healthy, lasting growth.