The best times of year for trimming are in early spring, right before new growth emerges, and in mid-summer, after the spring growth has hardened off.

The box hedge is one of the most iconic features of a formal English garden design. This evergreen shrub has a neat, compact growth habit that allows it to be trimmed and shaped into geometric forms and patterns. When left untrimmed, boxwood can grow into a rounded bush up to 5–6 feet tall and wide. But when regularly trimmed, it maintains a uniform shape and size.

The small, shiny green leaves of boxwood give off a pleasant herbal aroma when brushed against or trimmed. While native to parts of Europe and Asia, boxwood has been grown in British gardens since medieval times. Its popularity surged in England during Victorian times, when highly formal garden designs were in fashion. The boxwood hedge has become a staple part of the English garden, defining spaces, providing privacy, and creating living “walls” that can be sculpted into many shapes.

When to Trim Boxwood Hedges

Regular trimming is essential to maintaining the desired size and shape of a boxwood hedge. The best times of year for trimming are in early spring, right before new growth emerges, and in mid-summer, after the spring growth has hardened off. Here is a more detailed timeline:

Early Spring

Aim to trim boxwood in early spring before much new growth has occurred. This is generally late March or early April, but keep an eye on your hedge and local conditions. Trim when you observe some green starting to return to the branches but before major new leaf growth. Trimming at this time allows cuts to heal quickly with the flush of spring growth.

Mid-Summer

The second most important trim time occurs in mid-summer, typically in June or July. This trim removes spring growth that has hardened off and helps restrict excessive growth that can occur in the summer. Trimming off the long shoots that stick out also maintains the uniform shape of the hedge.

Avoid Trimming in late Autumn or Winter

While you can trim boxwood lightly into early autumn, it’s best to avoid significant cuts going into winter. Trimming off green growth at this time can stimulate tender new growth that will be damaged when cold weather arrives. Hard frosts can also prevent the cut branches from healing properly. Save any major reshaping trims for early spring.

Yearly Trimming Frequency

How often you need to trim your boxwood depends on how formal you want to keep it, how quickly it grows, and what shape it’s in. When kept in a highly formal shape, like dense, flat panels, boxwood might need trimming three or more times a year. Garden boxwood trimmed less formally may only need one or two trims. Monitor new growth and trim the hedge as needed to maintain the size and shape you desire.

Trimming Method

The easiest way to trim boxwood hedges is to use dedicated hedge shears. Handheld, cordless hedge trimmers work well for smaller hedges. For taller, denser hedges, long-handled styles give more leverage and power. Always use clean, sharp hedge shears to achieve a neat and even cut. Ragged cuts invite disease and make boxwood look unkempt. Take the time to trim methodically and precisely for the best results.

If making very minor growth adjustments, small hand pruners may also be used. Loppers are also useful for getting extended branches in the center of the hedge that hedge shears can’t always reach.

Caring for Boxwood After Trimming

Boxwood is relatively resilient, but be selective about timing major reshaping trims to reduce stress on the shrubs. After trimming, boxes may benefit from the application of balanced fertiliser to aid recovery. Water the hedge well after significant removal of foliage and going into winter to prevent desiccation damage.

Here is a useful link to the Royal Horticultural Society page on box hedges