Thuja plicata care: the quick checklist
- Trim once a year in late summer (August-September), or twice with a lighter cut in June and again in August.
- Only trim between May and September: dormant-season cuts leave dead tips.
- Stay in the green: never cut into brown wood, it will not regrow.
- Winter bronzing is normal. The foliage returns to green in spring.
- Always check for active bird nests before cutting (1 March to 31 August).
- Use a sharp trimmer or shears: blunt blades leave brown frayed tips.
- Keep the top slightly narrower than the base to stop lower sections dying out.
Thuja plicata is frequently confused with leylandii at the garden centre and in people's gardens. The two are not closely related and behave quite differently. Getting them mixed up is the most common reason for thuja care going wrong.
Thuja plicata vs leylandii: the short version
Leylandii (Cupressus x leylandii) grows at 60-90cm per year and needs trimming two or three times a season to stay manageable. Thuja plicata grows at 30-50cm per year, which means once or twice a year is plenty. The foliage on thuja is softer in texture, a brighter green, and has a distinctive cedar scent when cut. Both share the same one irreversible rule: do not cut into the brown, inner wood. See our full leylandii guide for why that rule matters so much with conifers.
Nesting season
The UK Wildlife and Countryside Act 1981 makes it an offence to damage or destroy an active bird's nest. Nesting season runs roughly 1 March to 31 August. A thuja hedge trimmed in late August is on the very edge of this window: check the hedge for active nests before you start. The safe cutting window with no legal risk is September to February, though trimming in the dormant period (November to April) should be avoided for the health of the hedge. Late August and September is the sweet spot.
Before you start
- Eye protection: safety glasses or goggles; conifer clippings travel further than you expect.
- Ear defenders: for petrol or electric trimmers over any significant distance.
- Gloves: sturdy gloves; the foliage oils can irritate skin on repeated contact.
- Electric trimmers and RCDs: always use a residual current device (RCD) with a corded trimmer, trailing the cable away from your working direction.
- Height: for hedges over 1.5m, a pole trimmer keeps you on the ground. If a ladder is needed, have someone footing it; never overreach sideways.
- Wasp nests and brambles: look into the hedge from the outside before starting. A wasp nest inside a thuja hedge is not obvious until you put the trimmer close to it.
When to trim
The trimming window for Thuja plicata is May to September. Outside this period the plant is dormant or slowing, and cuts made in winter or early spring leave brown, dead tips that do not green up until the following summer.
For most Kent gardens: one cut in late August or September is enough. This removes the season's growth, keeps the hedge within its allotted space, and the timing means no active nest risk.
For a very formal, tight hedge: a lighter first cut in June (once the spring flush has hardened), followed by the main cut in August, gives a crisper appearance through summer. In Kent's mild coastal climate, the growing season runs slightly later into autumn than further inland, so a September cut is never wasted.
The stay-in-the-green rule
This is the one rule for all conifers, thuja included. The brown, inner wood of the hedge does not carry dormant buds. Cut into it and you will have a permanent bare patch.
The green zone on a well-maintained thuja hedge extends 15-30cm in from the outside. Keep your cuts within that zone. If the hedge has been allowed to grow considerably wider than you want, reduce the width over two or three seasons rather than cutting back to the bare interior in a single aggressive cut.
Thuja is slightly more forgiving than leylandii at the boundary between green and brown, and will sometimes push limited new growth from old wood if there is good light. But do not rely on it: stay in the green.
Why the hedge goes bronze in winter
Thuja plicata's foliage turns a bronze or copper colour in cold weather. This is a normal physiological response: the plant reduces its chlorophyll production in cold, low-light conditions. It returns to bright green when temperatures rise in spring, typically from March onwards. In the milder winters along the East Kent coast, around Deal, Sandwich Bay and Eastry, the bronzing is usually less pronounced than in harder inland gardens.
If you see bronze patches in summer, or patchy browning inside the hedge rather than a general colour shift, that is a different matter. Patchy summer browning usually means the inner dead zone has been exposed by cutting too far back, or drought stress, or occasionally a root problem. Summer bronzing does not recover on its own; address the cause.
Keeping the shape
Aim for a profile that is wider at the base than at the top. A wedge shape (technically called a batter) lets light reach the lower branches and prevents the base from dying out. Even a slight angle, just enough that the base is 5-10cm wider than the top, makes a significant difference to the long-term health of the hedge.
A top that has been allowed to become wider than the base will eventually cause the lower foliage to thin and die. This is one of the most common problems we see on neglected thuja hedges in gardens across Worth, Ash and Woodnesborough.
Tools
A sharp hedge trimmer is the standard tool for thuja. The feathery foliage cuts cleanly with powered blades and the scale of most thuja hedges makes hand shears impractical for anything other than final tidying. Petrol trimmers give more power for a long run; a battery trimmer is fine for most garden hedges and significantly quieter. Keep the blades clean and sharp: blunt or resin-clogged blades bruise rather than cut and leave the foliage looking brown-tipped for weeks.
For the top of a tall hedge, a pole trimmer or long-reach battery trimmer keeps you on the ground and gives better overall control than working from a ladder. See our guide to choosing a hedge trimmer for a full comparison of the options.
Credit: the best4hedging channel's video "A focus on Western Red Cedar hedging: All you need to know about Thuja plicata" provides a thorough overview of the species from one of the UK's leading specialist hedging nurseries. Find it on YouTube by searching for that title or the channel name.
Rather we took it on?
We look after conifer hedges of all types across Sandwich, Deal, Worth, Ash, Woodnesborough, Eastry and Sandwich Bay. Send a photo for a free quote, most jobs booked the same week.