How to Stop Weeds Growing Through Fences

Few things cause more neighbour disputes than weeds crossing boundaries. You maintain your garden immaculately, but every few weeks you’re pulling out the same weeds that keep appearing along your fence line. The problem isn’t on your side. It’s coming from next door.

Understanding how common garden weeds cross boundaries helps you tackle the problem effectively. Some spread underground, some climb over, and some simply seed into your garden. Each requires a different approach.

How Weeds Cross Boundaries

The most persistent boundary weeds spread through underground root systems. These roots travel horizontally beneath the soil surface, emerging on your side of the fence metres away from the parent plant.

Couch grass is notorious for this. Its white rhizomes spread several metres per year, pushing through any gap in the soil and even growing through gravel boards at the fence base. A single plant on your neighbour’s side can colonise your entire border within a couple of seasons.

Bindweed does the same, but also climbs. Its roots spread underground while its twining stems grow up and over fences, scrambling through your plants and setting seed on both sides of the boundary.

Ground elder spreads through shallow horizontal rhizomes, typically in the top few inches of soil. It travels fast and regenerates from the smallest root fragment, making it particularly difficult to control when the source is on neighbouring land.

Other boundary invaders include horsetail, which sends roots down to two metres deep, and brambles, which spread both by underground suckers and by tip-rooting where arching stems touch the ground.

Your Legal Rights

In the UK, you have the right to cut back any vegetation that crosses onto your property, whether above or below ground. This is known as abating a nuisance and doesn’t require your neighbour’s permission.

However, there are important caveats. Any cuttings technically remain your neighbour’s property, so you should offer them back before disposing of them. You cannot enter their land without permission, even to deal with weeds affecting your garden. And you cannot cut back beyond the boundary line, even to prevent regrowth.

For most weeds, there’s no legal requirement for your neighbour to control them. The Weeds Act 1959 only covers five specific injurious weeds (ragwort, spear thistle, creeping thistle, curled dock and broad-leaved dock), and even then, enforcement only occurs if they’re spreading to agricultural land.

The exception is Japanese knotweed. Under the Wildlife and Countryside Act 1981, it’s an offence to cause Japanese knotweed to spread into the wild. If your neighbour’s knotweed is encroaching onto your property, you may have grounds for a legal claim, particularly if it affects your property value or causes structural damage.

Killing Weeds at the Fence Line

The first step is dealing with the weeds already on your side. Simply pulling them up rarely works with perennial weeds, as roots left behind regenerate within weeks.

A glyphosate-based weedkiller is the most effective solution. Apply it to actively growing weeds between April and October, when the chemical will be transported down to the roots. For established perennial weeds, expect to need two or three applications over a growing season. The strongest weed killer available gives you the best chance against persistent roots.

Because glyphosate is systemic, killing weeds on your side can weaken the connected root system on your neighbour’s side. This won’t eliminate the source, but it slows the rate of reinvasion.

For weeds growing directly against the fence, careful spot treatment with a gel formulation or paint-on weedkiller gives better control than spraying, reducing the risk of drift onto plants you want to keep.

Installing a Root Barrier

To stop underground rhizomes crossing the boundary, install a vertical root barrier along the fence line. This creates a physical wall that roots cannot penetrate.

Dig a trench along the inside of your fence, as close to the boundary as possible. The depth depends on which weeds you’re dealing with. For couch grass and ground elder, 30cm is usually sufficient. For bindweed, dig to at least 45cm. For horsetail, you’d need to go deeper than is practical, so barrier installation is less effective.

Line the trench with heavy-duty HDPE root barrier membrane, available from garden centres and online suppliers. The barrier should extend 5cm above soil level to prevent rhizomes growing over the top. Backfill the trench, compacting the soil to hold the barrier in place.

Root barriers work well but aren’t foolproof. Determined roots may eventually find their way around the ends, and the barrier does nothing to stop seeds or climbing stems.

Creating a Maintenance Strip

A gravel or paved strip along your fence line makes ongoing weed control much easier. It creates a clear zone where emerging weeds are immediately visible and easy to treat.

Dig out a strip 15-20cm wide along the fence base and lay landscape membrane to suppress weeds. Cover with decorative gravel, slate chips or pebbles. The membrane blocks light to prevent germination, while the gravel makes it easy to spot and remove any weeds that do push through.

This approach also solves the practical problem of mowing and strimming right up to the fence. Grass and weeds at the fence base are notoriously difficult to maintain, and a hard strip eliminates the issue entirely.

For a more permanent solution, lay brick or paving slabs as a mow strip. This prevents all weed growth when properly installed on a compacted base, though it’s more expensive and labour-intensive than gravel.

Talking to Your Neighbour

The most effective long-term solution is coordinated weed control on both sides of the fence. A difficult conversation now can save years of frustration.

Approach your neighbour diplomatically. Point out the specific weeds causing problems and explain how they spread underground. Many people simply don’t realise their garden is the source of a neighbour’s weed problem.

Offer to share the cost of treatment, or suggest treating both sides simultaneously for maximum effectiveness. With systemic weedkillers, treating both sides of a connected root system at the same time gives much better results than treating one side alone.

If your neighbour is unresponsive or the property is rented, you may need to contact the landlord or managing agent. For council properties, report persistent weed problems to your local authority.

When Neighbours Won’t Cooperate

If your neighbour refuses to address their weeds, focus on what you can control: your side of the boundary.

Maintain a barrier zone along the fence. Treat emerging weeds promptly before they establish. Install root barriers where practical. Accept that you’ll need to manage boundary weeds as an ongoing maintenance task rather than a one-off fix.

Document the problem with dated photographs if the situation is severe enough that you might consider legal action in future. For most common weeds, there’s little legal recourse, but for Japanese knotweed or situations where weeds are causing demonstrable damage, evidence of ongoing encroachment strengthens any potential claim.

Specific Problem Weeds

Different boundary weeds require different approaches.

Couch grass: Install root barrier to 30cm depth. Treat emerging growth with glyphosate. Creates dense mats that smother other plants.

Bindweed: Root barrier to 45cm minimum. Train climbing stems up canes before treating with glyphosate for better absorption. Repeated treatment needed over several years.

Ground elder: Shallow root barrier (20cm) often sufficient. Responds well to glyphosate but requires multiple applications. Very persistent.

Horsetail: Root barrier largely ineffective due to depth of roots. Focus on repeated removal and improving drainage. See our horsetail guide for detailed control methods.

Brambles: Cut back all growth on your side. Treat cut stumps with triclopyr or glyphosate gel. New suckers will emerge from roots crossing the boundary, requiring ongoing treatment.

Frequently Asked Questions

Can I spray weedkiller over the fence onto my neighbour’s weeds?

No. Applying any substance to your neighbour’s property without permission is trespass. You can only treat weeds on your own land, up to but not beyond the boundary line.

My neighbour’s garden is completely overgrown. Can the council force them to clear it?

Only in limited circumstances. Councils can act if the garden poses a health hazard or harbours vermin, but general untidiness or weed growth isn’t usually grounds for enforcement. The Weeds Act only applies to specific injurious weeds spreading to agricultural land.

Will a fence stop weeds spreading?

A fence stops nothing. Standard fences have gaps at the base, and underground roots pass beneath them without any resistance. Only a buried root barrier creates an actual obstacle to spreading roots.

How deep do I need to install a root barrier?

For most rhizomatous weeds like couch grass and ground elder, 30cm is adequate. For bindweed, go to 45cm or deeper. Horsetail roots go too deep for practical barrier installation.

My neighbour has Japanese knotweed. What can I do?

Japanese knotweed is different from common garden weeds. If it’s encroaching onto your property, document the situation and seek legal advice. You may have grounds for a claim under nuisance law, and the presence of knotweed can affect property values and mortgage availability.

Don’t let your neighbour’s neglect ruin your garden. Start by treating existing weeds with a strong weedkiller, then install barriers to prevent future invasion. For specific weed problems, see our guides to couch grass, bindweed and ground elder.