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Strimmer line for thick weeds: where 2.4 mm stops

Updated: October 2026

The round line is shredding the rough patch and leaving woody stems standing, so a square 2.4 mm reel looks like the next step. Strimmer line for thick weeds can be that step when the head already allows 2.4 mm and the growth is thick grass rather than a bramble hedge. It is not a substitute for the blade the manual lists, and a chain on the head is not that blade. Peter F. used Stihl UK, the Health and Safety Executive, and amazon.co.uk reviews captured on 19 October 2026. We did not cut a plot. A qualifying purchase can earn a commission at no extra cost to you. Packs for an edge or a long roll are on the [2.4 mm strimmer line comparison](/hub/lawn-and-garden-equipment/2-4mm-strimmer-line) and the [best 2.4 mm strimmer line](/hub/lawn-and-garden-equipment/2-4mm-strimmer-line/sub/2-4mm-strimmer-line-best) page.

The round line is shredding the rough patch and leaving woody stems standing, so a square 2.4 mm reel looks like the next step.

Our top picks

Viabrico Viabrico square 100 m

Best overall

Viabrico Viabrico square 100 m
9.2/10about £10.99
View offer
Stihl Stihl square 253 m

Alternative

Stihl Stihl square 253 m
8.6/10about £33.92
View offer
Oregon Oregon Nylium star 90 m

Alternative

Oregon Oregon Nylium star 90 m
8.2/10about £25.76
View offer
On this page
  1. 1.Thicker grass is what 2.4 mm square and star are sold for
  2. 2.Brambles are where the reviews stop agreeing
  3. 3.The next tool is the blade the manual lists
  4. 4.Look before you cut
  5. 5.Where the line stops

Thicker grass is what 2.4 mm square and star are sold for

Stihl UK describes square 2.4 mm as more aggressive than round, for thick woody grass and weeds, and mentions a brush knife. That likeness does not replace a blade the manual does not list. Oregon’s profile map points star at a cleaner cut and square profiles at denser vegetation. Serrated line at about 3 mm, and any 4.0 mm cord, is a different diameter. A square’s 2.4 mm is the side. Zeqeey prints a diagonal of about 3.4 mm. One Viabrico reviewer on a Stihl AutoCut C 3-2 says square is already the maximum that head will take.

Brambles are where the reviews stop agreeing

One Oregon Nylium 90 m review runs that five-edge line through brambles and nettles and accepts a shorter life. Another buyer returned it after breaks on ordinary nettles. Both sit in 50 United Kingdom reviews at 4.5 from 1,447. They do not add up to a blade. On the 360 m star, one UK review says brush and saplings need a blade. Stihl’s square is kinder on thick farm grass, then worse when a Honda head melted it. Mow and Edge draws the same stop: woody growth is where nylon ends.
Viabrico Viabrico square 100 m

Testsieger

Viabrico Viabrico square 100 m
9.2/10about £10.99
View offer

The next tool is the blade the manual lists

If the stems are still standing and the manual’s maximum is 2.4 mm, a sharper profile will not become a blade. The next tool is the single-piece metal blade the maker lists, with the matching guard and the harness. HSE’s chain-flail bulletin says EN ISO 11806 covers nylon strimmers and single-piece metal blades, not multi-piece attachments such as chains. Call a professional if you have not used that setup, or if the strimmer vibrates, smokes, or stalls on the correct cord with equal tails. A weld inside the head is heat and a bad wind.

Look before you cut

The RHS and the RSPCA both say strimmers injure hedgehogs. Check the grass before you start. A wild bird’s nest in use or being built is protected in England, Scotland, and Wales by the Wildlife and Countryside Act 1981. Northern Ireland uses the Wildlife (Northern Ireland) Order 1985. The RSPB’s practical caution for hedges is March to September. If you cannot see that the hedge is empty, leave it. Neighbour noise is a statutory-nuisance test under the Environmental Protection Act 1990. Line diameter does not set a legal hour.

Where the line stops

Use square or star 2.4 mm when the manual already allows that diameter, the eyelet passes the corner, and the growth is thick grass rather than wood. Treat a shorter life on brambles as the optimistic review, not as a blade in a nylon packet. If the stems are still standing, the next tool is the single-piece blade the maker lists, with the matching guard and harness, or a professional if that setup is new to you.

Common questions

Will it cut brambles the way a blade does?
No. One 90 m star user cuts brambles and nettles and loses line doing it. Another returned the same listing after breaks on ordinary nettles. A 360 m review says brush and saplings need a blade. Mow and Edge draws that same stop. Treat a shorter life on brambles as the optimistic review, not as a blade in a nylon packet.
What if the manual stops at 2.4 mm and the stems are woody?
Stay inside the manual. Shaped 2.4 mm is the most aggressive line this head is being sold, and it still may not cut woody stems. A 3 mm or 4.0 mm cord is a different diameter and can be too thick for this head. The next step is the blade the maker lists, or a professional if that blade, the harness, and the guard are new to you.
Is serrated 4.0 mm line part of this comparison?
No. ManoMano describes serrated line at about 3 mm and above, for powerful machines. A 4.0 mm listing is outside this set, including percentage claims that sat on one. Do not import those figures onto a 2.4 mm square or star. If your head’s maximum is 2.4 mm, a 4.0 mm reel is the wrong basket.
When do you stop and call someone?
Stop when the nylon head is not cutting woody scrub or saplings, when you would be fitting a metal blade you have not used with the harness and the matching guard, or when the machine vibrates, smokes, or stalls on the correct cord with equal tails. Also stop if you cannot confirm a hedge is empty. A longer reel does not move those limits.
Does a chain flail count as the blade the head can take?
No. HSE’s bulletin says EN ISO 11806 covers nylon strimmers and single-piece metal blades, not multi-piece metal attachments such as chains. Use the guard and the accessory the machine maker approves. A chain is not a workaround for 2.4 mm line that has reached woody stems.

Related pages

2.4 mm strimmer line buying guide

Square or round 2.4 mm strimmer line

2.4 mm strimmer line

Best 2.4 mm strimmer line for the job in front of you

How to fit strimmer line on a 2.4 mm bump-feed head

Sources

Shelf prices, star ratings and review counts are the amazon.co.uk figures captured on 19 October 2026. The other pages are public UK guidance on line profile, soak advice, vibration and garden safety.

  1. Stihl UK square 2.4 mm mowing line (retrieved 19 October 2026)
  2. Oregon UK Nylium Star 2.4 mm 90 m (retrieved 19 October 2026)
  3. Oregon profile map (retrieved 19 October 2026)
  4. ManoMano UK trimmer line buying guide (retrieved 19 October 2026)
  5. HSE chain flails and brush cutters (retrieved 19 October 2026)
  6. HSE INDG480 hand-arm vibration (retrieved 19 October 2026)
  7. RHS hedgehog-friendly gardening (retrieved 19 October 2026)
  8. GOV.UK noise nuisances (retrieved 19 October 2026)