SBK Brushwood Killer: what triclopyr is, and when it beats glyphosate
This is the answer to 'I sprayed it and it came back'. Triclopyr does not kill a woody weed by being stronger than glyphosate, it kills it by pretending to be a hormone. Here is what that actually means, the two SBK bottles and the one number nobody prints on either, and the cut-stump mix that puts twenty-five times more into a stem than any spray does.
By The Weed GuyLast updated
The short version
Brushwood killer means triclopyr, and in a UK garden centre triclopyr means SBK, because there are exactly two triclopyr products on the whole amateur register and Vitax makes both. It is a synthetic copy of a growth hormone, so broadleaved and woody plants wreck themselves on it while grasses mostly carry on. Reach for it when the weed is woody and it is growing through grass you want to keep. Reach for glyphosate when nothing green around it matters. And on anything with a cut stem, the lever that changes the result is not the bottle, it is painting the cut.
Triclopyr against glyphosate, on the things that decide it
Not a strength league table. Two different attacks on two different systems, which is why one of them leaves your lawn standing.
| Triclopyr (SBK) | Glyphosate | |
|---|---|---|
| Chemical family | Synthetic auxin, HRAC and WSSA Group 4 (the old HRAC letter code was O) | The only member of HRAC and WSSA Group 9, on its own |
| How it kills | Copies the growth hormone auxin and floods the signal, so cell division and elongation run out of control | Blocks one enzyme, EPSP synthase, shutting down the pathway that builds three amino acids |
| What it kills | Broadleaved and woody plants: brambles, nettles, dock, thistles, scrub, hardwood saplings, tree stumps | Essentially any green plant it lands on, woody perennials more slowly than annuals |
| What it spares | Grasses, largely. Not reliably a fine lawn, and nothing else broadleaved | Nothing. Overspray on a lawn leaves a dead print of wherever you swept the lance |
| What you see first | Twisting, curling and cupped leaves, sometimes within hours. That distortion is the tell it is working | Nothing for days, then yellowing, then collapse over two to four weeks |
| How you get it in | Leaves, and roots too. It moves in soil, which glyphosate does not | Green tissue only. Glyphosate is locked up on contact with soil |
| UK amateur products | Two. Both made by Vitax, both called SBK | 133 on the same amateur herbicide register, plus professional grades needing a certificate |
The product counts come off the HSE amateur register, which anyone can search. Filter it by triclopyr and it returns two results out of two. Filter the same register for glyphosate herbicides and it returns 133. That imbalance is the single most useful thing to know before you go shopping, because it means every "brushwood killer", "tough weed killer" and "glyphosate free stump killer" on the shelf is either one of those two Vitax bottles or it is not triclopyr at all.
What triclopyr actually does to a plant
Auxin is the hormone a plant uses to tell its own cells when to divide, how far to stretch and which way to lean. Triclopyr is a synthetic copy of it. Spray it on and the plant does not read it as an attack, it reads it as an instruction, and it obeys.
What follows is growth with the governor removed. Cell division and elongation run uncontrolled, the plant throws out misshapen leaves and swollen stems, and the whole hormone system it uses to regulate itself is jammed open. Ethylene production goes up with it, which is where the twisting comes from. That is the visible tell, and it is a useful one: within hours of a good application the leaves curl, cup and corkscrew. Nothing that only burns the leaf does that.
It is classified as Group 4 by both HRAC and the Weed Science Society of America, the synthetic auxin group. If you meet the old letter code O in an older document, that is the same thing, before HRAC moved to numbers in 2020.
One thing worth correcting, because it gets repeated: triclopyr does not destroy the plant's plumbing. It travels through it. The chemical moves in the phloem and xylem to the growing points, and that is precisely why it reaches a root crown when a contact weedkiller cannot. The plant dies of runaway growth and collapse, over days and weeks, not of anything being dissolved.
Why it spares grass, and the bit nobody admits
Anyone selling this stuff will tell you triclopyr kills weeds and not grass. That much is true, well documented and commercially exploited on a huge scale, which is why selective lawn treatments exist at all. Grasses take very little damage at label rates. Broadleaved and woody plants take a great deal.
Here is the part the retail copy leaves out. Plant scientists cannot fully explain why. The leading review of auxin herbicides, published in the Journal of Experimental Botany, says outright that the basis of the selectivity is still not fully understood, and lists three things that may all contribute: the anatomy of the plant's vascular tissue, how efficiently it detoxifies the chemical, and how its auxin receptors perceive it in the first place.
I would rather tell you that than pick whichever tidy explanation sounds best. It also changes what you do, because "reliably true but not fully understood" is exactly the kind of effect that has edges. Which is why the same label that promises grass safety also warns about fine turf, and why nobody should treat that warning as a printing error.
And what glyphosate does instead
Glyphosate does not imitate anything. It blocks a single enzyme, EPSP synthase, which runs the shikimate pathway. That pathway is how a plant manufactures three amino acids it cannot do without: tryptophan, tyrosine and phenylalanine. Shut it and the plant starves of its own building materials.
Every green plant runs that pathway, which is the whole reason glyphosate takes the grass along with the bramble. Animals do not run it at all, we get those amino acids out of food, which is the usual argument for its toxicity profile. Worth being precise though: some micro-organisms have the pathway too, so "only plants have it" is a bit neater than the truth.
It is also the only herbicide in its group. Triclopyr shares Group 4 with a crowd of other hormone mimics; glyphosate sits alone in Group 9 with nothing else aimed at the same target. If you want the arithmetic of getting a glyphosate concentrate into a tank at the right strength, that lives on the concentrate strengths and mixing rates page rather than here.
The two SBK bottles, and the number neither label puts on the front
One is 48 g/L and one is 3.6 g/L. That sounds like a thirteenfold gap and in the bottle it is. On the ground it is not, and working out why tells you which one to buy.
| What you are doing | The label mix | Triclopyr in it |
|---|---|---|
| Watering can with a fine rose, tough weeds | 30ml in 6 litres, over 10 square metres | About 0.24 g/L |
| Sprayer, tough weeds and woody weeds | 30ml in 1.5 litres, over 10 square metres | About 0.96 g/L |
| Ready to use SBK, straight off the trigger | Already mixed, nothing to add | 3.6 g/L |
| Cut stump by sprayer | 200ml of product to 300ml of water | About 19 g/L |
| Cut stump by brush | Equal volumes of product and water | 24 g/L |
| Neat out of the bottle | Not a labelled use, and not a thing to do | 48 g/L |
Look at rows two and three. The ready-to-use bottle, at 3.6 g/L, is roughly four times the strength of the concentrate mixed to its own sprayer rate. Everyone assumes a ready-to-use is the watered-down version for people who cannot be trusted with a measuring cap. On this product it is the opposite.
Take it one step further and it gets better. The concentrate label puts 30ml over 10 square metres, which works out at 0.144 grams of triclopyr on each square metre. The trigger bottle's own label says one stroke delivers 0.7ml and covers a weed 15cm across, which works out at 0.143 grams per square metre. Two different products, two different labels, and the dose landing on the plant is the same to within one per cent. Vitax never says this and neither does anybody else, but it is sitting there in both sets of instructions.
So the choice between them is not strength. It is money, area and reach. The concentrate is far cheaper per square metre and it is the only one of the two that can be mixed to the cut-stump rate. The trigger bottle is for spot-treating a handful of weeds without getting a sprayer out.
Why the mixing rates you find online all disagree
Search for the SBK dilution rate and you will be given 20ml in a litre covering seven square metres, 25ml covering eight and a half, 30ml in 1.5 litres covering ten, and 30ml in six litres covering ten. Four different answers, none of them acknowledging the other three. It looks like a mess and it is not one.
Divide each of them out and they land in the same place: about three millilitres of product per square metre of weed. The label's own two routes are the clearest proof. Thirty millilitres in 1.5 litres through a sprayer and 30ml in six litres through a watering can are printed as if they were different rates, but both put the same 30ml over the same 10 square metres. All that changes is how much water carries it, because a watering can with a fine rose puts down a great deal more liquid than a sprayer does.
Which gives you the number actually worth remembering. Three millilitres per square metre. Work out the area first, then the product, then whatever volume of water your kit needs to spread it evenly. That also explains the coverage claims on the packs: a 500ml bottle says it treats up to 166 square metres, and 500 divided by three is 166. The one rule that overrides all of this is to read the pack in your hand, because different pack sizes carry different mixing tables. Getting the water volume right is a sprayer question, and calibrating a knapsack sprayer is how you find out what yours actually puts down.
Which woody weeds this is actually for
The label names brambles, thistles, nettles, dock, other tough weeds, woody weeds and hardwood saplings, in grassland and other neglected non-crop areas. That last phrase is the boundary and it does real work, so it is worth reading twice.
- Brambles in grass. The classic case, and the one the label leads on. It is worked through properly on the bramble weedkiller pillar, including how it stacks up against the various Roundups, so I will not repeat it here.
- Ivy. Triclopyr is a fair call on ivy climbing through a hedge or up a tree in rough grass, and a poor one on a wall, where the problem is a stem and a root plate rather than a lawn. The sequence that actually works, and the falcarinol rash nobody warns you about, are on the ivy pillar.
- Nettles and dock along a verge. Both named, both at the same rate as brambles, because the label groups them together under tough weeds. This is where the grass safety earns its money.
- Hardwood saplings and scrub. The one rate on the label that is genuinely different. Saplings get 30ml in 1.5 litres by sprayer only, and the instruction is to cover leaves, branches and stems rather than to treat a set area. There is no watering-can option and no square metre figure, because you are wetting a structure, not dosing a patch of ground.
And the honest limits. Neglected non-crop areas is the labelled place for it, so a block-paved drive is not, and the grass safety that makes triclopyr the right answer in a lawn buys you precisely nothing in a paving joint. That is glyphosate territory, along with everything else that colonises block paving and gravel. I have also seen triclopyr credited with controlling horsetail. I could not corroborate that anywhere independent, so it is not a claim I will pass on.
Tree stumps: the strongest thing you can legitimately do with this bottle
A stump is not a weed, but it is the same problem in its purest form, and triclopyr is the standard answer to it. Two label routes, one target on the cut face, and a timing rule with a real reason behind it.
Start with the question the stump listicles never ask, which is whether the stump needs treating at all. Conifers die if they are cut to the stump. A pine, spruce, larch or fir will not come back and no chemical is required. Most native broadleaves are the opposite: ash, hazel, oak, sweet chestnut, field maple, small-leaved lime and willow all regrow strongly from a cut stump, which is the entire basis of coppicing. Birch and black poplar only really do it if they were cut young.
Then there is a third group where treating the stump does not help, and this is the one that catches people. Wild cherry, aspen, elm, white poplar and grey alder throw suckers from the root system rather than regrowing from the stump. You can dose that cut face perfectly and still watch shoots come up a metre away in the lawn, because you treated the part of the plant that was not the problem.
For everything in the middle group, here is what the label permits. Painting: equal volumes of product and water. Spraying: 200ml of product to 300ml of water. Either way, all cut surfaces and the bark down to soil level. Those work out at roughly 24 and 19 grams of triclopyr per litre, against about 0.96 in a foliar spray. Same bottle, same money, twenty to twenty-five times the concentration going into the plant.
Where you put it on the cut face matters more than most people realise. Forestry guidance is specific: treat the outer ring, roughly the outermost fifth of the stump just inside the bark, rather than flooding the middle. That living band is the tissue that still moves anything downward. The dead heartwood in the centre takes up liquid and does nothing with it.
Speed is the other half. Woody plants seal off damaged vascular tissue after injury, and the published window for water-based mixes is about five minutes. After that you are painting a lid. Cut and treat in one movement, brush already loaded, rather than felling the lot and coming back with the bottle. A stump cut last season is a much poorer prospect than one cut a minute ago.
Timing: autumn or winter, avoiding April, May and June. The label says so and forestry guidance gives the reason, which is that strong upward sap flow in early spring works against you. There is a field test for it, too. If the stump appears to bleed water after you cut it, the sap is running upward and you have picked the wrong month.
Two things on the stump-branded bottle. The ready-to-use SBK is not authorised for stumps: its label carries no stump instructions and its approval lists unwanted vegetation only, while the concentrate's approval explicitly includes unwanted vegetation (stump). Vitax's own website says the ready-to-use can be used on stumps, and the paperwork does not support that. And on SBK Tree Stump Killer, the paperwork points the other way: one safety data sheet covers both names as a single product identifier, there is no separate approval in the stump name, and at one retailer in August 2026 the stump-branded 250ml was 13.07 pounds against 7 pounds for 250ml of the concentrate. I cannot tell you the bottles are identical, because the barcodes differ and I have not had them side by side. I can tell you what the register says, which is more than either product page manages.
Where triclopyr is the wrong tool, and the warning that isn't on the label
The one that would genuinely catch me out, if I had not gone looking, is soil movement. Glyphosate is effectively switched off the moment it touches the ground. Triclopyr is not: it is taken up through roots as well as leaves, and it moves in soil. Published half-life figures range from around eight days to around ninety depending on soil and conditions, which is why the label gives you a flat six weeks before replanting rather than a number.
The practical consequence is one the label does not spell out at all. I read the whole artwork and the safety data sheet looking for it and it is not there. But herbicides in this family are a documented cause of injury to broadleaved trees and shrubs whose roots run under treated ground, and a tree's roots extend well past the edge of its canopy. So do not treat rough grass sitting over the root run of an ornamental tree or a hedge you care about. That is agronomy rather than a label instruction, and I would rather say where it comes from than dress it up as one.
The rest of the wrong-tool list is shorter. Hard surfaces, because the labelled area is grassland and neglected non-crop ground. Anything broadleaved you want to keep, because selective against grass is not the same as harmless, which is exactly why the label tells you to set the sprayer nozzle coarse rather than fine. Near water, because the classification is Aquatic Chronic 4 and the instruction is not to contaminate water with the product or its container. And a fine lawn, for the reason the label itself gives.
What to keep beside the SBK
SBK is the right answer for woody growth and it deliberately spares grass. For everything on the same plot that is not woody, including that grass, you need the other bottle.
What I’d use
Glyphosate concentrate, 360 g/L
Gallup Home & Garden Glyphosate Weedkiller (1 litre)
The one Gallup a homeowner can legally buy and use: a 1 litre glyphosate concentrate at 360 g/L, approved for home and garden use under MAPP 17672.
It is the same active, the same 360 g/L loading and the same isopropylamine salt as the professional Gallup XL, and its single label rate of 24 ml per litre of water is exactly the rate the professional labels reserve for perennial broad-leaved weeds. The difference between the two bottles is the authorisation printed on them, not the chemistry inside, and this is the side of that line you are allowed to stand on.
- Active ingredient
- Glyphosate, 360 g/L, as the isopropylamine salt
- Formulation
- Soluble concentrate you dilute yourself
- Approval
- MAPP 17672, labelled for use only as a home and garden weedkiller
- Mixing rate
- 24 ml per 1 litre of water, per the label
- Coverage
- 40 sq m per litre of made-up spray, so roughly 1,667 sq m per bottle
- Rainfast
- Rain within 6 hours may reduce effectiveness, per the label
- Size
- 1 litre of concentrate
Watch out for
- No measuring cap in the bottle. Check a cup arrives, or the dose is guesswork.
- One re-treatment a season, and it takes four weeks. Do not go again early.
- Not for lawns. It is non-selective and takes the grass too.
- Resellers dominate the listing, so check the label that arrives is Barclay.
- "Super strength" is keyword stacking. It is 360 g/L, same as professional Gallup XL.
That’s an affiliate link: buy through it and I earn a small commission at no extra cost to you. It doesn’t change what I recommend or what I say is wrong with it. More on how that works in the affiliate disclosure.
No brand pays for a mention here, and nothing on this page is a paid-for opinion. The card above is an affiliate link, so I earn a commission if you buy through it, at no extra cost to you. It buys no product a kinder write-up, which is why the watch-outs sit on the same card as the reasons to buy.
About this resource
I'm The Weed Guy, one bloke who is qualified to use professional weedkiller. Every concentration, dilution, application window and restriction on this page comes off the two Vitax pack labels themselves and off the HSE approvals behind them: SBK Brushwood Killer under MAPP 12711 and Vitax Ready to use SBK Brushwood Killer under MAPP 12597, both of which anyone can look up on the HSE amateur pesticides register. The mechanism comes from HRAC's classification and from university and government sources rather than from anybody selling weedkiller. The stump biology comes from forestry and conservation handbooks.
The arithmetic is mine, and I have shown it so you can check it: the grams per litre in each mix, the dose per square metre, and the comparison between the two products. The things I could not verify are not on this page. I could not source a single soil half-life figure, so you get the range. I could not find any authoritative statement of why grasses tolerate this chemistry, so the page says that instead of picking a plausible-sounding answer. Sycamore came up repeatedly in the regrowth lists and I could not confirm it, so it is not in mine. And one point of housekeeping: the current approval for both products runs to 31 March 2027 after an extension issued in April 2025, with existing stocks usable to September 2028. That is a routine extension of an approval period, not a withdrawal, and I mention it only because a date on a register gets misread as one.
Straight disclosure: nothing on this page is a paid-for opinion and no brand sponsors this site. SBK gets named repeatedly here for one unavoidable reason, which is that it is one of only two triclopyr products a UK gardener can legally buy, so a page about triclopyr cannot avoid being a page about Vitax. That is not an endorsement, and it is why this page carries the fine-turf line the retail listings leave off, the stump-bottle price gap, and the manufacturer web claim its own label does not support. How commercial arrangements work across the rest of the site is set out on the affiliate disclosure page.
Common questions
What is the active ingredient in SBK Brushwood Killer?
Triclopyr, at 48 grams per litre, present as the triethylammonium salt. It is a soluble concentrate you dilute yourself, approved under MAPP 12711 and held by Vitax. Triclopyr is a synthetic auxin, which means it copies a hormone the plant uses to control its own growth rather than poisoning it in any ordinary sense. There is no glyphosate in it, and the ready-to-use SBK in the trigger bottle is the same active at 3.6 grams per litre under a separate approval, MAPP 12597.
Is SBK a professional weedkiller? Do I need a certificate?
No, and this is worth being straight about because the reputation says otherwise. SBK's own label reads FOR USE ONLY AS A HOME GARDEN WEEDKILLER, and its HSE authorisation records the field of use as ONLY AS A WEEDKILLER with the user given as Amateur. It sits on the amateur register alongside the supermarket bottles. Anyone can buy it and anyone can use it. The certificate of competence question applies to products labelled for professional use, which SBK is not.
Will SBK kill my grass, or damage my lawn?
Both answers are on the same label, and the retail listings only ever quote the first one. The pack front says TARGETS WEEDS NOT GRASS and the back panel says it kills difficult weeds not grass. Then, a few lines into the instructions, the same label says it may cause damage to lawns and other fine turf. Both are true. A rough verge, a paddock or a scruffy bit of grass shrugs triclopyr off. A fine ornamental sward is a different plant community and it can mark. The ready-to-use bottle actually puts the whole thing in one honest sentence, saying it targets weeds not grass but may cause some damage to lawns and fine turf.
Which SBK do I need, the concentrate or the ready-to-use?
Cost and reach, not strength. Work the two labels through and they deliver almost exactly the same dose of triclopyr per square metre: the concentrate puts down 30ml over 10 square metres, and the trigger bottle's own figure of one 0.7ml stroke covering a 15cm weed comes out within one per cent of it. So the ready-to-use is not the weak version. What it cannot do is the cut-stump job, because stump treatment needs a strong mix and the trigger bottle has no stump instructions and no stump use on its approval. Concentrate for anything with a woody stem, trigger bottle for spot-treating a few weeds without mixing anything.
What is the dilution rate for SBK?
Thirty millilitres in 1.5 litres of water through a sprayer, or 30ml in 6 litres through a watering can with a fine rose, covering 10 square metres either way. Those look like two different strengths and they are, but the dose landing on the ground is identical: same 30ml, same 10 square metres, different amounts of water carrying it. That is why the various rates quoted online, 20ml in a litre, 25ml over 8.5 square metres, all come out at roughly 3ml of product per square metre. Hold on to the rate per square metre rather than the millilitres per litre, because pack sizes print different mixing tables, and read the bottle in your hand.
How do I use SBK on a tree stump?
Cut the stump low and flat, then treat the cut face straight away with a much stronger mix than you would ever spray. The label gives two routes: equal volumes of product and water painted on, or 200ml of product to 300ml of water sprayed on, covering all cut surfaces and the bark down to soil level. That is roughly 20 to 25 times the concentration of a foliar spray, out of the same bottle. Aim at the outer ring of the cut just inside the bark rather than the middle, because that living band is the part that still moves anything down to the roots. Do it in autumn or winter, and not in April, May or June when the sap is rising.
Why does a cut stump have to be treated straight away?
Because the cut face is only briefly open. Cut wood dries and woody plants seal off damaged vascular tissue after injury, and once that has happened you are painting a lid rather than dosing a living plant. Forestry guidance on water-based mixtures puts the window at about five minutes. In practice that means cutting and treating in one movement, brush already loaded, rather than clearing the whole lot first and coming back with the bottle. It is also why a stump cut last year is a much poorer prospect than one cut a minute ago.
Does every tree stump need weedkiller?
No, and a fair few of the ones people treat never needed it. Conifers die if they are cut to the stump, so a pine, spruce, larch or fir generally needs nothing at all beyond patience. What does regrow, strongly, is most native broadleaves: ash, hazel, oak, sweet chestnut, field maple and small-leaved lime are the vigorous ones, and willow with them. Birch and black poplar only really come back if they were cut young. There is a third group where treating the stump will not save you either, because wild cherry, aspen, elm, white poplar and grey alder sucker from the root system rather than from the stump, so the shoots appear a metre away in the lawn while the treated stump sits there doing nothing.
Is SBK Tree Stump Killer the same thing as SBK Brushwood Killer?
I cannot tell you the two bottles are identical, because they carry different barcodes and I have not had them side by side. I can tell you what the paperwork says, which is more than either product page does. Vitax publishes a single safety data sheet, and it is headed SBK BRUSHWOOD KILLER / SBK TREE STUMP KILLER as one product identifier. The HSE register carries no separate approval in the stump name, and MAPP 12711 already covers stumps, its authorised areas being listed as unwanted vegetation and unwanted vegetation (stump). At one retailer in August 2026 the stump-branded 250ml was 13.07 pounds and the concentrate 250ml was 7 pounds. Same volume, same firm, roughly double.
Triclopyr or glyphosate, which is better?
Neither, they answer different questions. Ask what you are prepared to lose standing next to the thing you are killing. If the answer is nothing, because it is a bramble in a lawn, nettles along a verge or scrub in rough grass, triclopyr is the pick and the grass survives. If the answer is anything goes, because it is a gravel drive, a paved joint or bare ground, glyphosate is the right call and it costs less. Glyphosate is not weaker on woody weeds, it is just indiscriminate, and triclopyr is not stronger, it is selective.
Is triclopyr safe near ponds, and what about pets?
Keep it away from water. The classification on the approval is Aquatic Chronic 4 with the statement that it may cause long lasting harmful effects to aquatic life, and the safety data sheet carries the instruction not to contaminate water with the product or its container. That comes with no hazard pictogram and no signal word, so it is a mild classification, but it is the one restriction on this product I would not bend. On pets and children, the label is specific and reassuringly plain: they can be allowed on treated areas after the spray has dried. Grazing animals are a separate rule, and they stay off until the foliage of anything poisonous like ragwort has died down.
Can I plant something where I have used SBK?
Not straight away. The label says to allow at least six weeks between application and replanting, which is the manufacturer telling you the residue matters rather than me guessing. That gap exists because triclopyr behaves differently from glyphosate in soil: glyphosate is effectively switched off the moment it touches the ground, while triclopyr is taken up through roots as well as leaves and stays active in soil for a while. Published half-life figures range from about eight days to about ninety depending on soil and conditions, which is why the label gives you a flat six weeks rather than a number.
How many times can I treat in a year, and how long does it take?
Two treatments per season, six weeks apart, and that cap is on the approval itself rather than being advice. Expect the visible signs within days, because the first thing a synthetic auxin does is distort growth, so twisting and curling leaves are the early tell. A full kill on anything woody takes considerably longer, and the label setting a six-week gap before you are allowed to go again is the honest guide to the timescale. Anything that browns off within hours has burned the leaf, not reached the root.