Thuja Hedges: Why Councils Are Starting to Ban Them

Anyone who now checks with the local planning office about planting a dense, evergreen hedge along the boundary of their plot is increasingly being told “no” - at least where thuja is concerned. The once-default hedge in suburban family neighbourhoods is coming under heavy pressure: councils are removing it from development and design codes, conservationists dismiss it as “green concrete”, and fire safety officers describe it as a ticking time bomb. What is driving this shift - and what does it mean in practical terms for your garden?

Councils versus Thuja: what’s behind the new bans

In strict legal terms, France - much like Germany - does not have a nationwide law that forbids thuja in private gardens. Instead, the leverage sits with local authorities and their development, landscaping or design plans. These are the documents in which city and municipal councils set out which tree and shrub species may be planted on street frontages, in new-build areas or within sensitive zones.

This is precisely where thuja is increasingly ending up on the no-go list. In many municipalities, uniform, monoculture thuja hedges are now treated as undesirable. If you are building a new home or substantially redesigning your plot, you are expected to follow these rules. Approval bodies tend to focus particularly on:

• fire risk along roads and between houses
• the impact on soil life and biodiversity
• the overall appearance of whole residential areas

Anyone who plants a prohibited hedge in defiance of clear requirements may face enforcement action. The municipality can order removal and impose fines. In France, sums of up to 1,500 euros are possible; similarly high penalties would also be conceivable in German-speaking countries if local authorities introduce comparable rules.

Thuja has shifted from former default to problem case: ecologically poor, highly flammable, often diseased - and therefore firmly on the authorities’ radar.

Thuja as “green concrete”: why biologists are raising the alarm

Many homeowners see thuja mainly as a simple way to block prying eyes. Conservationists judge it far more harshly. Bird and species-protection groups talk about a “green concrete block”: dense, sterile and close to useless for many animals.

The central criticism is that thuja creates an ecological no-man’s-land. Its scale-like foliage contains compounds that, as they rot down, can drive the soil’s pH sharply lower - often to readings below 5. In such acidic conditions, earthworms, many fungi and beneficial microorganisms struggle to survive. If a garden relies on thuja for decades, the soil in that strip can be degraded into a long-term problem area.

By contrast, mixed hedges made up of native shrubs provide an impressive base for wildlife. Specialists cite:

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

Given that roughly a third of native breeding birds are already considered at risk, the verdict on the thuja hedge is bleak: it offers very little food, few nesting opportunities, and alters the soil so strongly that even under the hedge, little may be willing to grow.

Fire risk in the front garden: when a hedge becomes a fuse

Alongside nature conservation, another factor is playing a major role in the new restrictions: preventative fire safety. Especially in periods of hot, long summers, plants with a high content of oils and resins move to the top of the risk list.

Thuja contains essential oils such as thujone, which are highly flammable. During dry spells, a single spark can be enough to ignite a long, dense hedge within seconds. Experts note that flames can shoot up an arid thuja wall in less than three seconds - at temperatures well above 800 degrees Celsius.

In tightly built-up estates, a hedge like this can act like a green fuse between a carport, a shed and the main house. A small fire - from a barbecue, fireworks or a carelessly discarded cigarette - can race along the planting at speed. Fire services know these spread patterns well, and for mayors they are a powerful argument for excluding thuja from sensitive locations.

Many thuja hedges are reaching the end of their life cycle

There is also a demographic factor. The major thuja boom dates back to the 1970s and 1980s. As a result, many estates today contain near-same-age, genetically very similar plants - often set just 70 to 80 centimetres apart and clipped tightly.

Hedges like this tend to hit their biological limit after about 40 years. They brown off inside, lose density, and become more vulnerable to drought and disease. In France, studies show that a large share of older thuja are already heavily affected by fungal infections, including Coryneum species that cause shoots to die back.

This has two outcomes: the hedge stops looking good, and it offers even less habitat. At the same time, dead sections can burn like tinder, increasing the hazard. This combination of age, illness and drought stress is pushing many municipalities to reduce widespread thuja belts over the long term.

What to do if your own thuja hedge comes under scrutiny

If you already have a large thuja hedge, there is no need to panic immediately. In most cases, municipal bans apply first to new plantings or major redevelopment work. Even so, the question may arise: is it worth phasing thuja out?

For old, weakened hedges, professionals often advise a decisive approach: remove it entirely and start again with a species-rich hedge. That may sound drastic, but it brings clear benefits - a better look, more wildlife in the garden, less fire load, and often lower maintenance over the long run.

Removing thuja properly: how to protect your soil

If you decide to take it out, it pays to work methodically. A sensible sequence is:

• Mechanical removal: lift out old trunks and roots using a spade, root spade or digger, depending on the hedge’s length and thickness.
• Loosen the ground: break up compacted soil deeply and dig out coarse root remnants wherever possible.
• Rebalance pH: work in about 50 litres of mature compost per linear metre and, if the soil is strongly acidified, add garden lime as well.
• Dispose of material: avoid using twigs and needles as mulch, as the terpenes they contain can inhibit new plants from germinating. Better options are a green-waste collection site or long composting with plenty of nitrogen-rich material.

The real work begins in the soil: if you acidify, you have to neutralise again - otherwise the strip under the former thuja hedge stays a growth desert.

Alternatives: hedge species councils are happy to see

Many towns and municipalities actively promote so-called “field-edge hedges” or “nature conservation hedges”. What they mean are rows planted with several native shrubs that provide flowers, fruit and structure. These plantings are often treated as showcase projects for improving biodiversity in built-up areas.

The usual recommendation is a mix of at least four to five native species. Commonly favoured choices include:

• hornbeam
• hawthorn (red or white)
• hazel
• dogwood species
• blackthorn or wild roses

These shrubs may not grow as perfectly “ruler-straight” as a tightly clipped thuja hedge, but in return they offer a full buffet of blossom, berries and places to hide. If you cannot do without privacy, you can plant taller species more densely towards the back and use more flowering shrubs on the street-facing side.

Care guidance: when pruning is allowed

One important consideration for gardeners is bird protection. In many countries, there is a seasonally restricted pruning ban during the nesting period, or at least strong guidance to manage hedges gently. Major cut-backs are best kept for late autumn or early winter - roughly November to December.

At that time, works no longer disturb breeding birds, and the plants can recover well the following spring. If you trim regularly but avoid overly harsh cuts, you also maintain shape while encouraging a dense, healthy structure.

Grants and practical tips for redesigning

In France, some regions already specifically support switching from conifer hedges to native mixed hedges, in some cases with subsidies per shrub planted. Similar schemes exist in parts of Germany, Austria and Switzerland, often under headings such as “climate-adapted green infrastructure”, “habitat networks” or “living gardens”.

If you want to replace an old thuja hedge, it is therefore worth asking your municipality first whether there are local grants or free advice from environmental departments. In some places, councils contribute fixed amounts per linear metre of hedge or arrange discounted group orders for native woody plants.

You can plan a new hedge in a practical way by thinking in layers: lower, flowering shrubs at the front, taller species behind for privacy and structure. Individual trees - for example field maple or rowan - can break up the look and create additional habitat.

What garden owners should do now

If you are planning a new build or making major changes to your front garden, ask early at the town hall about the local requirements. Many disputes can be avoided if the preferred hedge species is agreed with the planning department in advance.

Owners of older thuja hedges can take time to assess how vigorous their plants still are and whether a switch makes sense. Visible fungal damage, pronounced browning inside the hedge and repeated drought stress are signs in favour of a planned replacement. Those who take this step gain, over the medium term, not only a more attractive and lively plot - they also reduce fire risk and make their garden better suited to a hotter, drier summer routine.