Thistle identification: creeping, spear and Scotch thistle
Which one you have decides whether this is a weekend or a three-year campaign. Spear thistle is a biennial that spreads only by seed, so cutting it before mid-July genuinely ends that plant. Creeping thistle is one root system that expands about six metres a year and regrows from a 3mm fragment, so pulling the top is theatre. And the plant most people call Scotch thistle is often neither, and was probably planted on purpose.
By The Weed GuyLast updated
The short version
Run a finger down the flowering stem. Smooth and spineless means creeping thistle, a perennial you will never dig out. Spiny wings up the stem means spear thistle, a biennial you can finish with one well-timed cut. A huge white-woolly stem 10cm across means cotton thistle, which is usually a border plant somebody bought. The identification is the diagnosis here, not trivia.
The three-second test, and then the full key
Thistles usually get described in prose, which leaves you comparing paragraphs. Here they are side by side. The stem column is the one that settles it fastest, because creeping thistle is the only common UK thistle whose stem is neither winged nor spiny.
| Thistle | Stem (check this first) | Leaves | Flowerhead and height |
|---|---|---|---|
| Creeping thistle (Cirsium arvense) | Smooth and spineless. Branched, grooved, and never winged. If your thumb can run down the stem without being stabbed, you have this one. | Greyish-green, lance-shaped to oblong, spiny along the margins, with wavy edges. The upper leaves sit straight on the stem with no stalk. | Pale lilac, small, only 15 to 25mm across, often in loose clusters of two to five, and genuinely fragrant. Roughly 30cm to 1.2m tall. |
| Spear thistle (Cirsium vulgare) | Spiny wings running up the stem, right to the top, lightly hairy and cottony with it. The stem itself will hurt you. | Deeply cut into long lance-shaped segments, each tipped with a needle-like spine. Dull green and prickly-hairy on the upper surface. | Reddish-purple, much bigger at 20 to 40mm, carried singly or up to three per stem. The bracts are straight and each ends in a yellow spine. Around 1 to 1.5m. |
| Cotton thistle, sold as "Scotch thistle" (Onopordum acanthium) | Massive. Up to 10cm wide at the base, with broad vertical spiny wings and the same white woolly felt that covers the leaves. | Huge, 10 to 50cm wide, deeply lobed, long stiff spines along the edges, and covered in white woolly hairs that make the whole plant look grey. | Globe-shaped, 2 to 6cm across, dark pink to lavender. Up to about 2.5m in the wild and taller in a fed border. |
Characters are from the BSBI thistle key and NatureSpot species accounts. One honest wrinkle on height: Defra puts mature spear thistle at 30 to 50cm, while the botanical sources give one to one and a half metres. That is agricultural framing against a flowering plant in a garden, and I have used the botanical figure because it is the one you will be looking at. Broader identification across the rest of the common weeds sits on the UK weed identification keys. That page routes you to the right species; this one settles which thistle you have and what it means for getting rid of it.
What that identification actually buys you
This is the half the identification pages leave out and the removal pages skip past. Naming the plant is only worth doing because the three species are three completely different jobs.
| Thistle | Life cycle | How it actually spreads | What that means you do |
|---|---|---|---|
| Creeping thistle | Perennial | One connected root system. Lateral roots expand around six metres a year and have been recorded down to two metres. Seed is the sideshow: 4,000 to 5,000 per plant and only about 3 per cent of it viable. | Nothing you pull, fork or rotavate ends it, and cultivation actively makes it worse. Treat it as a root job repeated over seasons, not a weekend. |
| Spear thistle | Biennial | Seed, and nothing else. A rosette in year one, a flowering stem in year two, then that plant dies whatever you do. | Stop the seed and you have stopped the plant. Defra puts the deadline at cutting before mid-July, and digging one out works. |
| Cotton thistle | Biennial | Seed only, from a stout fleshy taproot under a first-year rosette. Not native to Britain, and more often planted than arrived. | Deadhead before it seeds and lift the rosettes you do not want. Check nobody put it there on purpose first. |
Spear thistle gets called an annual often enough to be worth correcting. Defra's own guidance note is explicit that it is biennial and spreads only by seed, and that single fact is the difference between a job you can finish this July and one you cannot.
Creeping thistle: you are not fighting a plant, you are fighting one root system
The thing standing in front of you is a shoot. The plant is underground and it is much bigger than the patch you can see. BSBI's account records lateral roots expanding up to six metres a year and reaching two metres deep on occasion, with each root capable of throwing up new shoots along its length.
Which sets up the trap almost every gardener falls into. Root pieces as small as three to six millimetres can produce new buds. The RHS describes the roots and rhizomes as brittle and regenerating easily when broken up by digging. And Defra states it without hedging: cultivation is not effective control, because it increases the number of root pieces that throw up new shoots. Forking a creeping thistle patch out is propagation with extra steps, which is the same mechanism that punishes people who dig ground elder or bindweed.
Seed matters less than it looks. AHDB puts a plant at four to five thousand seeds, ten to a hundred per head, of which only around three per cent are viable, and Defra says invasion is more often by root spread than by seed. All that thistledown blowing across the garden is mostly not the problem. The roots under the fence are.
There is a genuinely odd fact worth knowing here. Creeping thistle is close to dioecious, meaning male and female flowers sit on separate plants. AHDB notes the sexes need to be within a few hundred metres of each other for seed to be fertile, and BSBI puts the working distance at around thirty metres. Both sources caution that the separation is incomplete and some plants are self-fertile, so this is not a rule you can bank on. But it does explain a big isolated patch that flowers beautifully every year and never seems to seed: it may well be one clone of one sex.
One more reason it shrugs off spraying that has nothing to do with roots. AHDB points at the waxy coating on the leaves reducing herbicide adhesion. So you are fighting poor uptake at the leaf and enormous reserves at the root, at the same time.
Spear thistle: the one you can genuinely finish
Everything that makes creeping thistle miserable is absent here, and hardly anyone says so. Defra's guidance note is one sentence long on the point that matters: spear thistle is biennial and only spreads by seed.
Follow that through. A spear thistle spends its first year as a flat rosette, throws up its spiny-winged flowering stem in the second, sets seed, and dies. It has no creeping roots, no lateral spread, nothing running under the fence. So if you stop the seed, you have stopped it, and the plant in front of you was going to die anyway.
Defra gives the deadline plainly: cut each year before mid-July to prevent viable seed being shed, and digging them out also works. That is a real, dated, sourced instruction, and I could not find it repeated on a single consumer page about thistles.
The practical version, if it is one plant or a scattered dozen rather than a field: take the rosettes in the first year while they are still flat and the taproot is short, or take the stems before mid-July in the second. Getting the taproot matters because a snapped crown can push up a new stem, which is the same reason a dandelion snapped off at 5cm is back in a fortnight. Unlike creeping thistle, a broken bit of spear thistle root does not become a new plant somewhere else, so a puller that leaves a fragment behind is a nuisance here rather than a disaster.
Scotch thistle is two different plants, and usually not a weed at all
This is the search that goes most wrong, and it goes wrong twice.
First problem: the name points at two species. In a nursery, Scotch thistle means Onopordum acanthium, the cotton thistle, a grey woolly giant with a stem you could not close your hand around. But the government's own injurious weeds identification leaflet records Scotch Thistle and Bell Thistle as alternative names for spear thistle. Same phrase, two plants, and one of them is on a statutory list the other is not.
Second problem, and it is the bigger one. Cotton thistle is not native here. BSBI's Plant Atlas lists it as an archaeophyte in Britain, and notes it has increased since the 1960s possibly as an escape from gardens where it is frequently grown for ornament. In Scotland the Botanical Society of Scotland records it as non-native, cultivated and casual, introduced from France in the mid to late sixteenth century. It is sold, deliberately, as an architectural border plant.
So a fair chunk of what a UK reader finds under "how to get rid of Scotch thistle" is either a nursery selling it, or American and Australian control advice, because Onopordum is a declared noxious weed in both of those countries and is nothing of the kind here. Before you treat one, work out whether it arrived or whether somebody planted it. If you do want it gone, it is a biennial with a taproot and no creeping habit, so deadheading before seed set and lifting the rosettes is the whole method.
For completeness, since it comes up: nobody can pin Scotland's emblem to one species. The Botanical Society of Scotland notes the thistle on James III's 1470 coinage was identified as spear thistle, that later Stewart coins carry something more like cotton thistle, and that the thistle in the old story about the barefoot Norse raider could not have been cotton thistle because it had not been introduced yet.
Why a weed puller is the right tool for two of these and the wrong one for the third
Same principle as everything else on this page, applied to what is in your hands. A long-handled taproot puller is a genuine answer to spear thistle and cotton thistle, because both are biennials sitting on a single taproot with nothing creeping sideways. Grip the rosette, take the root, and that plant is finished.
Point the same tool at creeping thistle and you are working for the weed. Every root piece you snap off and leave behind can produce new buds from three to six millimetres up, which is why Defra puts cultivation down as ineffective rather than merely slow. The tool is not the problem, the species is. That is the whole argument for identifying the plant before you buy anything to use on it.
Two practical limits worth knowing whatever you have. A puller lifts a plug of soil and leaves a hole, which is fine in rough grass and annoying in a kept border. And it does nothing at all in a paving joint or in gravel, where the root is wedged rather than planted and a completely different set of tools applies.
Two labels give opposite timings, and both are right
Search thistle spraying and you get early spring, before 15cm, late summer and autumn, all asserted, none sourced. Here is where the contradiction actually comes from, which turns out to be chemistry rather than disagreement.
The amateur Roundup Ultra label, a 360 g/L glyphosate concentrate approved under MAPP 18850, puts thistles in its row for tough perennial deep-rooted and broad-leaved weeds at 15ml per litre of water over 30 square metres, against 10ml for annual weeds. Its when-to-treat cell is specific: bindweed, ground elder and thistles get treated "around the time of flowering". Thistles also carry one of only two asterisks in that row, and the footnote says some tough weeds may need a repeat treatment if regrowth appears. That is the manufacturer, on the pack, telling you one pass may not do it.
Now the other one. Corteva's Thistlex Pro, a clopyralid-based professional product, says the opposite: apply when thistles are actively growing at 150 to 300mm, before flowering, between 1 March and 31 July. Defra's guidance sits alongside it, putting MCPA at the early bud stage and noting one clopyralid application is normally enough.
Both are correct, and the reason is how the two actives travel. Glyphosate moves with the plant's own sugars. Bayer's best-practice note spells out what that means at the wrong moment: at stem extension the flow is pushing hard upwards to build flowerheads, so glyphosate sent down against that flow gives an initial good kill followed by regrowth. You want the sugar flow heading down to the root sink, which is what "around the time of flowering" is describing. Clopyralid is a different class working on young actively growing tissue, so it wants the plant small and vegetative. Same weed, two chemistries, two opposite right answers.
One honest limit. The Roundup Ultra label says "Thistles" without naming a species, so it is not telling you it means creeping rather than spear. And Thistlex Pro is a professional product, which Defra flags in general terms: some products are restricted to holders of a certificate of competence. It is quoted here because its label explains the mechanism, not because you can buy it in a garden centre. Which strength of glyphosate you can, and what to mix, is on the concentrate strengths and mixing rates page, and the general timing question on when to spray weeds.
The other useful line from the Thistlex Pro sheet applies whatever you are spraying: if the thistles have already reached flowering stage, top them and spray the regrowth at 150 to 300mm to get optimal root kill. Cut, wait for enough leaf to absorb through, then treat. Expect one to four weeks before anything looks dead on a glyphosate treatment, and note that rain within six hours of spraying may reduce how well it works. Nothing here is fast, and how long weed killer takes to work covers why.
For the non-chemical route on creeping thistle, Defra gives a window too, and phrases the outcome carefully: cut at flower stem extension but before the buds open, and repeated cutting at that same stage over several years may wear an infestation down. Read that again. Wear down, over several years. That is the honest ceiling on mowing, and it is the same grinding pattern as a nettle stand, which shares the 5 litres per hectare band with both thistles on the professional Roundup ProActive grassland table.
The Weeds Act 1959, read properly
Two of these three thistles are on a statutory list, which sounds far more alarming than it is. I read the Act itself rather than repeating what other pages say about it.
Section 1 names five injurious weeds and no others, by common name and Latin name together: spear thistle, creeping or field thistle, curled dock, broad-leaved dock and ragwort. Note the statutory name for creeping thistle is "creeping or field thistle". Cotton thistle is not on it. Neither is marsh, musk or welted thistle. The Act does allow the Minister to add species by regulation, and none have been added.
Here is the part that gets mangled everywhere. The Act does not make it an offence to have these plants. Section 1 gives the Minister a power: where he is satisfied the weeds are growing on land, he may serve a written notice on the occupier requiring action within a specified time to prevent the weeds from spreading. The duty is created by the notice, and even then the duty is to prevent spreading, not to remove the plants.
If a notice has been served and unreasonably ignored, section 2 makes that an offence carrying a fine not exceeding level 3 on the standard scale, with a further offence if it is still not remedied fourteen days after conviction. Only the Minister can bring proceedings, so a neighbour has no private route. Section 3 is the sharper end: the Minister can do the work and recover the reasonable cost, and unrecovered cost can become a charge on the land.
In practice it runs through Natural England, and the published thresholds are worth knowing before anyone threatens anyone. The complaint form is only open between 1 April and 30 September. The infestation has to be extensive rather than localised, at more than ten harmful weeds per square metre on the complainant's land, and they must already have asked the landowner to act. The land at risk has to be agricultural: grazing, forage or crops. Government guidance sums the standard up plainly, that you can have injurious weeds growing on your land but you should stop them spreading onto neighbouring agricultural land.
The Act extends to England, Wales and Scotland but not Northern Ireland, and in Wales the notices are issued by Rural Inspectorate Wales. The only amendment worth mentioning came from the Ragwort Control Act 2003, which added a code of practice for ragwort and added no new species. None of this is legal advice.
Before you kill it: thistles are worth something
The removal pages never raise this and the wildlife pages never mention control, so the reader gets one half or the other. The RHS position on creeping thistle in a garden is that there is no need to use a weedkiller on it at all.
The reason is specific rather than sentimental. The RSPB points out that a goldfinch's fine beak is exactly what lets it get at seeds other birds cannot reach in thistles and teasels. The RHS lists bees taking nectar and pollen from creeping thistle, small tortoiseshell, peacock and meadow brown butterflies on the flowers, painted lady caterpillars feeding on it, six-spot burnet moths visiting, and goldfinches, greenfinches, siskins and lesser redpolls on the seed, with the thistledown going into nests. The Wildlife Trusts say the same of spear thistle for goldfinches and the small copper butterfly.
So the verdict I would actually give. On a boundary with farmland, in a paddock, or running through a border, deal with it, and creeping thistle spreading toward a neighbour is the case where doing nothing has a cost. At the bottom of a garden, on a rough corner, or if it turns out to be marsh thistle in a damp patch, leaving it alone is a defensible answer rather than laziness. Defra makes the same point more formally for sites of conservation interest, where it says to take expert advice before acting at all.
What to put on thistles
Creeping thistle spreads along lateral roots, which is why taking the tops off multiplies it. A systemic concentrate, on before flowering, is what reaches the running root.
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. The botanical characters here come from the BSBI thistle identification key, BSBI's species accounts and Plant Atlas, and NatureSpot. The biology comes from AHDB and the RHS. The timings and life cycles come from Defra's guidance note on controlling harmful weeds, from the approved amateur Roundup Ultra label under MAPP 18850, and from Corteva's technical sheet for Thistlex Pro. The law I read directly on legislation.gov.uk rather than taking anyone's word for it.
Where sources disagree, I have said so rather than picking one quietly. Defra puts mature spear thistle at 30 to 50cm and the botanical sources put it at one to one and a half metres. The RHS gives creeping thistle around 200 seeds a flowerhead where AHDB gives ten to a hundred. Defra's note also carries its own caveat that its herbicide recommendations were under review, so I have used it for life cycles, cutting timings and the mechanism rather than treating its active-ingredient list as current.
Where I could not verify something, it is not here. I have not put a pound figure on "level 3 on the standard scale", because I did not verify the current amount. I have not claimed Weeds Act enforcement is rare, because no official statistic exists to support it, only published thresholds you can read yourself. And I have not stated a seed count for spear or cotton thistle, because I could not find a published one.
No brand sponsors this site and nothing here is a paid-for opinion. Products are named on this page only where the label or the tool type carries a real fact, which is why the Roundup Ultra and Thistlex Pro labels appear and no shopping list does. Elsewhere on this website some links do earn a commission, and the full position on that is on the affiliate disclosure page.
Common questions
What is the difference between creeping thistle and spear thistle?
Look at the stem, then at the life cycle, because those two facts decide everything else. Creeping thistle has a smooth, spineless stem and small pale lilac flowerheads of 15 to 25mm, and it is a perennial that spreads by an underground root system expanding around six metres a year. Spear thistle has spiny wings running up the stem to the top and much larger reddish-purple heads of 20 to 40mm, and Defra states plainly that it is a biennial that spreads only by seed. So a well-timed cut genuinely finishes a spear thistle and does almost nothing to creeping thistle.
How do I know what type of thistle I have?
Run a finger down the flowering stem before you look at anything else. Creeping thistle is the only common one with a stem that is neither winged nor spiny, which is why the botanical keys open with that character. If the stem carries spiny wings and the plant is around a metre to a metre and a half with big reddish-purple heads, it is spear thistle. If the stem is enormous, broadly winged and covered in white wool with grey felted leaves up to 50cm wide, it is cotton thistle, the one sold in garden centres as Scotch thistle. Flowerhead size is the second-best check: 15 to 25mm for creeping, 20 to 40mm for spear, 2 to 6cm for cotton.
Why does creeping thistle keep coming back after I dig it out?
Because you are not digging out a plant, you are breaking up a root system into more plants. BSBI records that root pieces as small as 3 to 6mm can produce new buds, and the RHS describes the roots and rhizomes as brittle and regenerating easily when broken by digging. Defra says it outright: cultivation is not effective control, because it increases the number of root pieces that throw up new shoots. Every fork-full is propagation. That is the single most useful thing to know about this species and almost nobody puts it in writing.
Is Scotch thistle the same as cotton thistle?
Usually yes, and confusingly not always. In a garden centre, Scotch thistle means Onopordum acanthium, the cotton thistle: a grey woolly biennial up to about 2.5m with globe-shaped heads. But the government's own injurious weeds leaflet records Scotch Thistle and Bell Thistle as alternative names for spear thistle, Cirsium vulgare, which is a completely different plant. So the same phrase points at two species depending on who is using it, which is exactly why this page describes the plant rather than trusting the label.
Which thistle is Scotland's national flower?
Nobody can pin it to one species, and the honest answer is more interesting than a name. The Botanical Society of Scotland puts the two candidates as spear thistle and cotton thistle, and points out that the thistle on James III's 1470 silver coins was identified as spear thistle, while the squatter thistle on later Stewart coins resembles cotton thistle. The catch is chronological: cotton thistle was introduced to Scottish palace gardens from France in the mid to late 16th century, so the thistle in the old story about the barefoot Norse invader could not have been it. Off-topic for killing anything, but it explains the naming mess.
Are thistles illegal in the UK?
No, and the popular version of this is wrong in a specific way. Creeping thistle and spear thistle are two of the five injurious weeds named in the Weeds Act 1959, along with curled dock, broad-leaved dock and ragwort. But the Act does not make having them an offence. It gives the Minister a power to serve a written notice on the occupier of the land requiring action within a set time to prevent the weeds from spreading. The offence is failing to comply with a notice that has actually been served on you. Cotton, marsh, musk and welted thistle are not on the list at all. None of this is legal advice.
Can my neighbour make me remove thistles?
Not directly, no. Only the Minister can bring proceedings under the Weeds Act, so a neighbour has no private route: they can complain to Natural England, and the published thresholds are specific. The complaint form only runs between 1 April and 30 September, the weeds must have spread widely onto their land at more than ten harmful weeds per square metre, and they must already have asked you to deal with it. The land at risk also has to be agricultural, meaning grazing, forage or crops. Government guidance puts the standard plainly: you can have injurious weeds on your land, but you should stop them spreading onto neighbouring agricultural land. Not legal advice.
When is the best time to kill thistles?
It depends which chemistry you are using, and that is why the advice you find contradicts itself. The amateur Roundup Ultra label gives thistles a named window of "around the time of flowering", which fits how glyphosate moves: it travels with the plant's sugars, so you want the flow heading down to the roots. Bayer's own best-practice note says that at stem extension the flow is pushing hard upwards to build flowerheads, and glyphosate sent against it gives an initial good kill followed by regrowth. The professional clopyralid products go the other way and specify 150 to 300mm and before flowering, because that active works on young growing tissue. Both are right for their own chemistry.
Does mowing get rid of thistles?
It ends spear thistle and it manages creeping thistle. Because spear thistle spreads only by seed, Defra says cutting each year before mid-July prevents viable seed being shed, and that is genuinely the whole job for that species. For creeping thistle the same guidance is more modest: cut at flower stem extension but before the buds open, and repeated cutting at that same stage over several years may wear an infestation down. Note the wording. Wear down over several years, not clear this summer.
How deep do thistle roots go?
Creeping thistle roots have been recorded down to about two metres on occasion, though the working answer is sideways rather than down: the lateral roots expand roughly six metres a year, which is how a single plant becomes a patch and then a field edge. Spear thistle and cotton thistle are a different shape of problem, both carrying a stout taproot under a rosette with no creeping habit at all. That is why a taproot puller is a real tool against two of these three species and a propagation device against the third.
Is sow thistle a real thistle?
No, though it gets listed as one often enough. Sow thistle is Sonchus, a different genus entirely, and the giveaway is that it is not properly spiny and it carries many flowers on a branched stem. Milk thistle is a third genus again. Among the true UK thistles you might actually meet, marsh thistle is tall and slender with small dark purple heads in damp ground, musk or nodding thistle has large reddish-purple heads that flop distinctively to one side, and welted thistle is another winged-stem Carduus. None of those four is named in the Weeds Act.
Should I get rid of thistles at all?
Depends entirely where it is, and I would rather say that than pretend every thistle is a problem. The RHS position on creeping thistle in a garden is that there is no need to use a weedkiller on it. Thistles are a serious wildlife asset: the RSPB notes that a goldfinch's fine beak is what lets it get at thistle seed in the first place, and the RHS lists bees, small tortoiseshell, peacock and meadow brown butterflies, painted lady caterpillars and six-spot burnet moths on creeping thistle, with goldfinches, greenfinches, siskins and lesser redpolls taking the seed and the down going into nests. In a paddock, on a boundary with farmland, or spreading through a border, deal with it. At the bottom of the garden, leaving it is a legitimate answer.