My griselinia hedge needs cutting and I'm not sure of the window. The questions we get every autumn.
Griselinia has become one of the most common evergreen hedges in Rochester gardens over the last couple of decades, and it comes with a specific set of questions, mostly around timing and what to do after a hard winter. Here's how the conversation usually goes.
Q. What actually is griselinia, and why has it become so common in Rochester gardens?
A. Griselinia littoralis is a New Zealand native, an evergreen shrub with large, glossy, apple-green leaves that forms a dense privacy screen surprisingly quickly. It took off in UK suburban gardens from the 1990s onwards because it establishes fast, tolerates urban pollution and coastal exposure, and handles the chalk-and-clay soils you get across Rochester and the Medway valley without much complaint. I'd say one in ten new hedging enquiries we get now is griselinia, most of them from the Frindsbury and St Margaret's side of the city where gardens are sheltered enough for it to thrive. It is not a native species and it has no particular wildlife value compared to hawthorn or hazel, but as a privacy screen in a manageable space it does the job well.
Q. When do you actually cut griselinia? I keep getting different answers.
A. Once a year, late summer into early autumn, is the right rhythm. Late August to mid-September is the standard window we use in Rochester. By that point the main flush of new growth has hardened off and the plant is not being pushed by active growth, so it takes the cut cleanly. Cut too early, in June or July, and you trigger a second flush of soft growth that can be caught by the first autumn frost. Cut in October or November and the cut ends are going into winter without time to firm up, which leaves them vulnerable to dieback in a cold spell. The late-August-to-September window aligns with what we use for holly and escallonia for the same reasons.
Q. Does the nesting bird law apply to my griselinia? It is a pretty dense hedge.
A. Yes, fully. Section 1 of the Wildlife and Countryside Act 1981 makes it a criminal offence to damage or destroy an active bird's nest, with an unlimited fine, up to six months' imprisonment, or both. The Act does not specify species of plant: any hedge dense enough to hold a nest is covered, and griselinia is dense enough that blackbirds and dunnocks nest in it regularly. GOV.UK gives 1 March to 31 August as the main nesting season, and we treat that window with the same caution we would a native hedge. The honest line is: light trimming with a nest check immediately before cutting is usually fine in the season, but we will not do hard reduction or renovation work on griselinia between March and August. The late-August-to-September window we use for the annual cut falls just on the right side of that, which is part of why we use it.
Q. My griselinia took a bad hit in last February's cold snap and half the leaves went brown and crispy. Does it need to come out, or will it recover?
A. Frost damage is griselinia's main weakness in the UK, and this is the question we get most in late winter from Wouldham and Cuxton, where the valley floor can push a few extra degrees below zero compared to the city itself. The good news is that the root system and the main woody framework usually survive temperatures that have scorched all the foliage. Do not cut the damaged stems back immediately: wait until late April or May, when you can see exactly where new growth is re-emerging from, then cut back to just above the first healthy bud. Cutting in February or March removes material that was still providing some frost protection to the crown. Most griselinia hedges in Medway valley gardens come back from moderate frost damage with twelve months of recovery, and a hard renovation later that summer will often bring them back to a presentable screen by the following autumn.
Q. Can griselinia take a hard renovation cut if it has grown well past its original size?
A. Yes, and this is one of griselinia's genuine advantages over some other evergreens. Unlike leylandii, which will not regenerate from old brown wood, griselinia will push new growth readily from mature stems, provided there is some green material left. We typically stage hard renovation over two years: hard cut to the sides in the first autumn, reduce the top in the second. If the hedge has been neglected for a long time and the main stems are thick, I'd do the sides one autumn and wait until the following September to take the height, giving the plant a full growing season to recover before the second cut. The one limitation is that the re-growth will need two to three seasons before it fills back in completely, so if you are expecting a solid screen immediately after renovation, manage that expectation before we start. For the general renovation approach that applies across species, our overgrown hedge renovation Q&A has the detail on staging and timing.
Q. My property is near the Rochester Conservation Area boundary on the Boley Hill side. Does that change anything?
A. If any individual tree within or adjacent to your griselinia hedge has a stem diameter exceeding 75mm at 1.5 metres from the ground, you are in section 211 of the Town and Country Planning Act 1990 territory. That requires a six-week notice to Medway Council before any pruning or removal work. Griselinia grown as a hedge, kept to typical garden hedge dimensions, will rarely reach that stem threshold on its own, but if a griselinia has been left to grow unchecked and developed substantial woody stems, it is worth measuring before we start. If you are inside the Conservation Area boundary itself (the Boley Hill and Cathedral precinct area of Rochester is the densest part of it), we always check the stem diameter on any specimen that looks large before quoting. Getting it wrong is not worth the risk: the penalty provision at section 210 carries an unlimited fine. Our Conservation Area Q&A covers the rules in full.
Q. I am on the exposed side near Delce and someone told me griselinia will not make it through a bad winter there. Is that true?
A. Partially. Griselinia is rated hardy to around minus 10 degrees Celsius in the RHS assessment, which covers most UK winters including most Rochester winters. The risk in more exposed positions, the higher ground at Delce or the open stretches near Nashenden, is a combination of hard frost with desiccating wind, which strips moisture from the foliage faster than the roots can replace it. In a sheltered courtyard or a walled garden with a south or west aspect, griselinia handles Rochester winters without difficulty. In a fully exposed north-facing run with no wind protection, a hard winter can strip it back significantly. If you are on an exposed site and want an evergreen with similar speed of establishment, Portugal laurel or the broader-leaved hollies are more reliably frost-hard, and our species choice Q&A covers the site-by-site comparison in more detail. That said, plenty of Delce gardens do have griselinia hedges that have stood for fifteen years without issue: it is a question of degree of exposure, not a hard no.
If your griselinia is approaching its annual cut and you are uncertain whether it falls within the nesting window, our hedge cutting timing Q&A covers the wildlife law in more detail, including what constitutes a light trim versus the kind of heavy work that needs to wait. If frost damage over the winter has left you with a hedge that looks beyond saving, the renovation Q&A covers the honest criteria for what is worth attempting and what is not.
Want us to look at your griselinia?
Send your postcode, a rough description of the hedge (height, length, how long since last cut), and any frost damage visible, to hello@rochesterhedges.co.uk, or call or WhatsApp 07763 100 477. We will give you a straight quote with the right timing for the plant, not just the earliest available date.
Sources: Wildlife and Countryside Act 1981, section 1; GOV.UK, Countryside hedgerow protection (nesting birds, 1 March to 31 August); Town and Country Planning Act 1990, sections 210 and 211 (Conservation Area notices); Royal Horticultural Society, Griselinia littoralis hardiness and cultivation notes.