How to Kill Weeds Under Hedges

The strip of ground beneath a hedge is one of the most challenging areas in any garden. Dry shade, root competition and restricted access create conditions where ornamental plants struggle but tough weeds flourish. Left unmanaged, this zone becomes a reservoir of weeds that spread into surrounding borders and lawn. Check our guide to common weed species to identify what you’re dealing with.

Clearing weeds from under hedges requires different techniques than open ground. You’re working in confined spaces, often on hands and knees, with hedge roots competing for every drop of water and nutrient. But with the right approach, you can bring even the most neglected hedge base back under control.

Why Weeds Thrive Under Hedges

The conditions beneath hedges favour a specific group of tough, shade-tolerant weeds. Understanding why they succeed here helps you choose effective control methods.

Dry shade is the defining characteristic. Hedge canopy intercepts rainfall before it reaches the ground, while the dense root system of established hedges extracts moisture from surrounding soil. Most garden plants can’t compete, but certain weeds have adapted to exactly these conditions.

Ground elder spreads through white underground rhizomes that can extend several metres from the parent plant. It tolerates deep shade and dry soil, often arriving under fences from neighbouring gardens. Once established, it’s extremely difficult to eradicate.

Ivy thrives in shade where other plants fail. Its evergreen leaves photosynthesise year-round, and stems root wherever they touch soil. Ivy spreads along hedge lines and can eventually climb into the hedge itself.

Nettles indicate nitrogen-rich soil, often from accumulated leaf litter. Their spreading yellow roots form dense colonies that exclude other plants. Nettles die back in winter but return vigorously each spring.

Other common hedge-base weeds include brambles, cleavers, hedge bindweed and various grasses. Many arrive as seeds deposited by birds perching in the hedge above.

Clearing the Ground

Before any control method works effectively, you need access to the weeds. This often means lifting the hedge canopy to create working space beneath.

Remove the lowest branches from the hedge to about 45cm above ground level. This exposes the base for weeding and spraying, improves air circulation to reduce fungal problems, and makes future maintenance far easier. Most hedging plants respond well to this treatment and quickly fill any gaps in their upper growth.

Clear accumulated debris, fallen leaves and dead vegetation. This material often harbours weed seeds and provides cover for slugs and snails. Rake it out and compost it, or bag it for green waste collection if it contains weed roots or seeds.

For light infestations, hand weeding may be sufficient. Work when soil is moist, using a border fork to loosen roots. With perennial weeds like ground elder, try to follow and remove the entire root system, though in practice you’ll always miss some fragments.

Chemical Control

Serious infestations of perennial weeds usually require herbicide treatment. Glyphosate is the most effective option, absorbed through leaves and transported to roots to kill the entire plant.

Spray when weeds are actively growing, typically April to September. Ensure good leaf coverage but avoid runoff. Glyphosate works best when weeds have plenty of foliage to absorb the chemical.

Protect the hedge from spray drift. Although most established hedging plants tolerate minor contact with glyphosate, direct spraying causes damage. Use a pressure sprayer with a cone nozzle held close to targets, and spray only on still days.

For weeds growing close to hedge stems, use glyphosate gel rather than spray. Paint it directly onto weed leaves with the built-in applicator. Gel stays where you apply it with no drift risk.

Ground elder and ivy often require multiple treatments over two or three growing seasons. Their extensive root systems contain enough stored energy to produce new growth even after the first application kills visible foliage. Retreat any regrowth promptly before it builds root reserves.

For woody weeds like brambles and tree seedlings, cut stems close to ground level and apply glyphosate gel or a triclopyr brushwood killer to the fresh cut surface. This delivers herbicide directly into the root system. For the toughest infestations, the strongest weed killer available provides the best results.

Smothering With Mulch

After clearing or treating weeds, a thick mulch layer suppresses regrowth and prevents new weed establishment. Under hedges, where you’re not trying to grow other plants, you can use heavier smothering methods than in borders.

Lay cardboard or several sheets of newspaper over cleared ground, overlapping edges by at least 15cm. This blocks light to any remaining weed roots and prevents seeds germinating. Cover with 10-15cm of bark mulch, wood chips or composted material.

For persistent weeds like ground elder, consider using weed membrane beneath the mulch. Landscape fabric allows water through while blocking light completely. It’s more expensive than cardboard but lasts several years.

The mulch layer needs topping up annually as organic material breaks down. Each time you add fresh mulch, you extend the smothering effect and continue suppressing weed growth.

Dealing With Specific Problems

Ground elder spreading from neighbouring gardens presents an ongoing challenge. Even if you clear your side completely, new growth pushes through from roots extending under the fence. Install a vertical root barrier of heavy-duty plastic or metal edging, buried at least 30cm deep along the boundary. This blocks rhizome spread while allowing the hedge roots through.

Ivy climbing into hedges needs cutting at the base and treating with herbicide on the cut stems. Don’t try to pull ivy out of the hedge, as this damages branches and bark. Let the cut portions die and dry before removing them.

Nettles in large patches respond to repeated cutting. Slice them down every few weeks through the growing season, and you’ll gradually exhaust the root reserves. Alternatively, one or two applications of glyphosate in early summer usually gives complete control.

Tree seedlings, particularly ash and sycamore, germinate freely in the sheltered conditions under hedges. Remove them while small by pulling or digging. Larger saplings need cutting and treating with brushwood killer to prevent regrowth from the stump.

Preventing Reinfestation

Once you’ve cleared the hedge base, ongoing maintenance prevents weeds returning to their former dominance.

Check under hedges monthly during the growing season. Remove any weed seedlings while small, before they establish deep roots or set seed. A quick pass with a hoe or hand weeding takes minutes but prevents hours of future work.

Maintain the mulch layer at 10cm depth minimum. Top up each spring before annual weeds germinate. The consistent cover makes any breakthrough growth obvious and easy to spot.

Keep the hedge base clear of fallen leaves and debris where seeds can hide and germinate. A quick rake in autumn removes this seed bank before spring.

Consider planting tough ground cover plants that can compete in dry shade. Vinca, pachysandra and some hardy geraniums tolerate these conditions and, once established, leave little space for weeds to colonise.

Frequently Asked Questions

Will weedkiller damage my hedge?

Established hedges tolerate minor contact with glyphosate, but direct spraying causes damage. Use a low-pressure sprayer held close to targets, avoid spraying on windy days, and consider gel formulations near hedge stems.

How do I stop ground elder spreading from next door?

Install a vertical root barrier along the boundary, buried at least 30cm deep. Heavy-duty plastic or metal edging blocks the spreading rhizomes. You’ll still need to treat any ground elder already on your side.

Can I use a selective lawn weedkiller under hedges?

No. Selective herbicides target broadleaf plants while sparing grass. They’ll damage or kill most hedging plants. Use only non-selective herbicides like glyphosate, applied carefully to weeds only.

How long before I see results from glyphosate?

Visible effects typically appear within one to two weeks, with complete kill taking three to four weeks. Perennial weeds may regrow from roots and need repeat treatment.

What’s the best time to clear weeds under hedges?

Late spring to early summer is ideal. Weeds are actively growing so absorb herbicides effectively, and you have the full season ahead to treat any regrowth. Avoid winter when growth stops and herbicides are less effective.

The strip beneath your hedge doesn’t have to be a weed-infested eyesore. With persistent effort and the right techniques, you can transform it into a low-maintenance zone that no longer supplies weeds to the rest of your garden. For more on tackling the toughest garden weeds, see our guides to weeds at lawn edges and common garden weeds.