Thuja hedges under pressure: why councils are moving against them

If you ask a planning department today whether you may plant a dense, evergreen hedge along your boundary, the answer is increasingly likely to be a firm no - at least when Thuja is involved. What was once the default hedge in suburban streets is now coming under intense scrutiny. Local authorities are removing it from their development plans, conservation groups describe it as “green concrete”, and fire specialists call it a ticking time bomb. So what is driving the backlash, and what does it mean for your garden?

For many homeowners, the appeal of Thuja has always been obvious: it is fast-growing, evergreen and effective at blocking views. Yet planners are now weighing that convenience against broader concerns such as fire safety, ecological value and the visual character of whole neighbourhoods.

Local authority rules on Thuja hedges: what is behind the new restrictions

Legally speaking, there is still no nationwide ban on Thuja in private gardens in France - just as there is no blanket prohibition across Germany. The decisive power sits with local councils and their development or design plans. In those documents, municipal and town councillors decide which tree and shrub species are permitted along street fronts, in new estates or in particularly sensitive areas.

That is exactly where Thuja is increasingly landing on the red list. In many places, uniform monoculture Thuja hedges are now viewed as undesirable. Anyone building a new home or reshaping a plot has to follow these rules. Approval officers are especially attentive to:

• the fire risk along roads and between buildings
• the impact on soil life and biodiversity
• the visual appearance of entire residential areas

If someone plants a prohibited hedge despite clear rules, they may face enforcement action. The council can demand that it be removed and may issue fines. In France, penalties of up to €1,500 are possible, and similar sums would be quite conceivable in German-speaking countries if local authorities set out comparable regulations.

Thuja is shifting from standard garden staple to problem plant: poor for wildlife, highly flammable, often unhealthy - and therefore firmly on the radar of the authorities.

Thuja hedge, biodiversity and fire risk: why biologists are raising the alarm

Many homeowners see Thuja as a simple way to keep out prying eyes. Conservationists judge it far more harshly. Bird and species-protection organisations describe it as a “green concrete block”: dense, sterile and almost useless for most animals.

The main criticism is that Thuja creates an ecological dead zone. Its scale-like needles contain substances that, as they decompose, can push soil pH sharply downwards - often below 5. In soil this acidic, earthworms, many fungi and beneficial microorganisms struggle to survive. If a garden relies on Thuja for decades, the affected strip of soil can be left as a long-term problem area.

By contrast, mixed hedges made up of native shrubs provide a remarkable habitat. Specialists point to:

• up to 35 mammal species that can feed or shelter in a varied hedge
• around 8 species of bats that hunt there
• more than 100 insect species that use flowers, leaves, bark or dead wood
• up to 80 bird species that find nesting sites and berries

Against the backdrop that around one third of native breeding birds are already considered at risk, the verdict on the Thuja hedge is grim: it offers very little food, few nesting opportunities and alters the soil so strongly that little else will thrive beneath it.

A further ecological drawback is that evergreen monocultures tend to be poor at supporting layered habitats. A mixed hedge with staggered flowering and fruiting periods gives animals something to use across the seasons, whereas a single-species screen offers a much narrower benefit.

When the hedge becomes a fuse: fire danger in the front garden

Alongside nature conservation, another argument is central to the new restrictions: preventive fire protection. In an era of hot, prolonged summers, plants with a high oil and resin content are receiving greater attention.

Thuja contains essential oils such as thujone, which are highly flammable. During dry spells, a single spark is often enough to set a long, dense hedge alight within seconds. Experts say flames can race up a dried-out Thuja wall in less than three seconds, reaching temperatures well above 800 degrees Celsius.

In tightly built-up neighbourhoods, such a hedge acts like a green fuse running between a carport, a garden shed and the house itself. A small ignition source - perhaps from a barbecue, fireworks or a carelessly discarded cigarette - can spread rapidly along the hedge. Fire brigades know this pattern well, and for mayors it is a strong reason to keep the plant out of sensitive locations.

Many Thuja hedges are reaching the end of their lifespan

There is another factor: the major Thuja boom took place in the 1970s and 1980s. As a result, many estates now contain hedges of almost the same age, with very similar genetics, often planted just 70 to 80 centimetres apart and clipped tightly into shape.

After roughly 40 years, such hedges reach their biological limit. The plants turn brown on the inside, lose density and become vulnerable to drought and disease. In France, studies show that a large share of older Thuja plants are already heavily affected by fungi, including Coryneum species that cause shoots to die back.

This has two consequences: the hedge no longer looks attractive, and it offers even less habitat. At the same time, dead sections become more likely to burn like tinder. It is precisely this combination of age, disease and drought stress that is prompting many councils to reduce the spread of Thuja hedging over the long term.

What should you do if your Thuja hedge comes under scrutiny?

If you already have a large Thuja hedge, there is usually no need to panic immediately. In most cases, municipal restrictions apply first to new planting or to major alterations. Even so, it is worth asking whether a gradual replacement would make sense.

Experts often recommend a clear-cut approach for old, weakened hedges: remove them completely and replace them with a species-rich hedge. That may sound drastic, but it brings several benefits: better looks, more wildlife in the garden, lower fire load and, in the long run, often less maintenance.

Removing Thuja properly: how to recover your soil

If you decide to take the hedge out, a structured approach is best. A sensible sequence is:

• Mechanical removal: Take out old trunks and roots with a spade, root spade or digger, depending on the hedge’s length and thickness.
• Loosen the soil: Break up compacted ground thoroughly and remove any large root remnants where possible.
• Balance the pH: Work in around 50 litres of well-rotted compost per linear metre and, if the soil is strongly acidic, add garden lime as well.
• Dispose of the material: Do not use branches and needles as mulch, because the terpenes they contain can inhibit the germination of new plants. Better options are a green-waste facility or long composting with plenty of nitrogen-rich material.

The real work begins in the ground: if the soil has been acidified, it must be neutralised again - otherwise the former Thuja hedge remains a dead zone for growth.

Alternatives: which hedge species councils are happy to see

Many towns and councils actively promote what are often called “field-edge hedges” or “wildlife hedges”. These are rows made up of several native shrubs that provide blossom, fruit and structure. Such planting schemes are seen as a showcase for greater biodiversity in built-up areas.

The usual recommendation is a mixture of at least four or five native species. Favoured choices include:

• hornbeam
• common hawthorn or white hawthorn
• hazel
• dogwood species
• blackthorn or wild roses

These shrubs do not grow in the perfectly straight, ruler-like manner of a clipped Thuja hedge, but they repay that with a full menu of blossom, berries and hiding places. If privacy is essential, you can plant denser, taller species towards the rear and use more flowering shrubs on the street side.

For a more natural-looking boundary, it also helps to think in layers: lower shrubs at the front, medium-height species in the middle and taller plants or small trees to break up the outline. That approach softens the visual effect while still preserving screening.

Pruning guidance: when the shears are allowed

One important point for garden owners is bird protection. In many countries, the breeding season brings a temporary ban on pruning or, at the very least, a strong recommendation to trim hedges only with great care. Larger cuts are best carried out in late autumn or early winter, typically in November or December.

At that time, nesting birds are no longer disturbed, and the plants can recover well in the following spring. If you trim regularly but avoid severe cutting, you can keep the shape while encouraging a dense, healthy structure.

Funding and practical tips for reshaping your hedge

In France, some regions already support the shift from conifer hedges to native mixed hedges, sometimes with grants per shrub planted. Similar programmes exist in parts of Germany, Austria and Switzerland, often under headings such as climate-adapted planting, habitat networks or living gardens.

If you want to replace an old Thuja hedge, it is worth asking your council first whether local grants or free advice from environmental officers are available. In some areas, local authorities contribute fixed amounts per linear metre of hedge or help arrange discounted group orders of native shrubs.

When planning the replacement, it helps to design the hedge as a layered system. Low flowering shrubs can go at the front, taller species behind them for screening and structure. A few trees - such as field maple or rowan - can open up the composition and create extra habitat.

What garden owners should do now

If you are planning a new build or major changes to your garden, check the local rules at the town hall early on. Many disputes can be avoided if the intended hedge type is agreed in advance with the planning department.

Owners of older Thuja hedges can calmly assess how healthy their plants still are and whether a switch would be worthwhile. Visible fungal damage, heavy browning inside the hedge and repeated drought stress are all signs that replacement should be considered. Taking that step not only gives you a more attractive and lively plot in the medium term; it also lowers fire risk and helps prepare your garden for hotter, drier summers.