In general, privet should be trimmed in late spring, after any frosts but before the main flowering period.

Privet is arguably the most popular choice for garden hedging in the United Kingdom. This hardy, fast-growing shrub offers year-round privacy and security when trimmed into a dense, leafy barrier. The smooth, evergreen foliage of privet provides a classic manicured look, while the small summer flowers attract bees and other pollinating insects.

When and how often to trim a privet hedge depends on the desired look and formality. In general, privet should be trimmed in late spring, after any frosts but before the main flowering period. This allows time for new growth to harden off before winter. Give privet a lighter shaping trim in mid-summer to keep it tidy if needed. For formal, rectangular privet hedges, plan on trimming up to three times a year in the spring, summer, and autumn. This maintains a tight shape and compact growth habit.

It’s best to avoid heavy pruning in the autumn, as new growth can be damaged by the cold winter weather. Leave any major renovations or rejuvenation of overgrown vegetation until early spring each year. Trim privet with cordless or manual hedge trimmers for easier maintenance. Wear protective equipment when working with power tools.

Choose the popular oval-leaf privet (Ligustrum ovalifolium) or golden privet (Ligustrum x vicaryi) for classic medium-height hedging. Trim fast-growing California privet (Ligustrum ovalifolium) annually to keep its broad leaves under control. For lower-growing borders, Ligustrum vulgaris works well. No matter the variety, trimming privet at the right time of year will keep this beloved British hedging looking tip-top.

Here is the RCH page on privet