UK weed identification, and when not to trust an app
Most of the questions people ask about identifying a weed are really questions about photo apps. So here is the straight answer on those, and then the thing no app will do for you: work out whether being wrong actually matters. For the thirteen ordinary UK weeds keyed out below, it almost never does. For two other plants, giant hogweed and Japanese knotweed, being wrong is a burn or a house sale.
By The Weed GuyLast updated
The short version
Point Google Lens at it. On a common weed in flower it will usually give you the right name, it costs nothing, and it is already on your phone. Then apply the only test that matters: what does a wrong answer cost you? For almost everything on the table below, nothing. Hoe it, pull it, or treat it, and the exact name barely changes what you do. For two UK plants a wrong answer is expensive: giant hogweed, whose sap burns skin in sunlight, and Japanese knotweed, which affects mortgages and property sales. Neither is in the table below, and on neither should you accept a phone's word for it. Read the identification pages here, and get a person to confirm it.
Yes, the apps work. Here is exactly where they stop working
Weed identification advice tends to write as though photo recognition does not exist. That is not honest, and it is not useful, because it is the first thing anybody does.
Google says on its own page for Lens that it will "Identify plants and animals", with "Find out what plant is in your friend's apartment" as the worked example. It is free, it needs no download if you already have the Google app or Chrome, and the camera icon in the search bar is where it lives. On an iPhone there is a version built into Photos, which Apple files in the iPhone user guide under "Identify objects in your photos and videos". I could not get Apple's own article to load to check what it claims about plants, so I am not going to put words in their mouth about how well it does on a UK weed. Try it and see.
Notice what neither company's page carries: any accuracy caveat at all. That is normal for a product page and no use to you, so here are the four ways a photo identification goes wrong, in the order I would worry about them.
- You photographed the wrong part of the plant. This is the commonest failure by a long way. People photograph the flower, because it is the pretty bit, and the flower is often the least distinctive thing about a weed. White umbels sit on top of four different plants in the table further down this page, two of which you should treat very differently. What separates them is the stem and the leaf join. Photograph that.
- Lookalikes a picture genuinely cannot separate. The willowherbs are the clearest case: NatureSpot notes they hybridise commonly and that reliable identification needs photographs showing the four-lobed stigma as well as the leaf shape. When the reference sources say a close-up of one flower part is required, a snap of the whole plant was never going to get there.
- Seedlings. Most weeds look nothing like themselves in their first few weeks, and the first few weeks are exactly when it is easiest to deal with them. The season when the answer is most useful is the season the app is least reliable.
- Variegated and coloured garden forms. A variegated or purple-leaved version of a plant does not match the photographs the model learned from. Worth knowing because several of these plants have garden forms people have deliberately planted, including a variegated ground elder that spreads perfectly well despite being sold as the well-behaved one.
None of that makes an app a bad idea. It makes it a first pass. Use it, then check the answer it gives you against a written description of the plant, which is what the rest of this page is.
The stakes decide whether a guess is good enough
This is the bit no app listicle will tell you, and it is the whole of my advice on identifying weeds.
Before you trust any identification, from a phone or from a page like this one, ask what a wrong answer costs. Almost always the answer is nothing. If you think a plant is chickweed and it turns out to be mouse-ear chickweed, you hoe it either way and nothing whatsoever has gone wrong. Twelve of the thirteen weeds in the table below sit in that category, and on those you should be quick and unbothered. Guess, hoe, move on.
Two UK plants break that rule, and they break it in different ways.
- Giant hogweed costs you skin. Its sap does very little on its own; sap on skin followed by sunlight causes severe burns and blistering. A wrong identification here is not an untidy border, it is a hospital conversation, and strimming or mowing something you have misidentified makes the exposure worse because it puts sap in the air. This is one of the two places on this whole website where my advice is to do nothing yourself. The full identification and safety page on giant hogweed covers the stem markings, the size, what the sap actually does and the first-aid sequence. Go and read that rather than trusting anything on this page, and go and look at a real photograph before you go near the plant.
- Japanese knotweed costs you money. It affects mortgage lending, it appears as a direct question on the standard property information form when you sell, and it has produced real court cases between neighbours. A wrong answer either way is expensive: miss it and you have a problem you have not budgeted for, call it wrongly on a plant that is actually a dock and you have talked yourself into a survey you did not need. The knotweed identification page works through the zigzag stem growth, the hollow purple-speckled canes and the plants it gets confused with, and explains why a specialist survey rather than a spray bottle is the next step.
So the rule I would hold to is simple. Low stakes, use the phone and get on with your day. High stakes, use your eyes on a written key, get a real photograph in front of you, and then get a person to confirm it. An app is very good at telling you what a plant is called. It has no idea at all what it is going to cost you.
Thirteen UK weeds people cannot name, and how to name them
These are the thirteen that come up in search constantly with almost nobody asking how to get rid of them, which tells you they are an identification problem rather than a weed problem. Each one gets a row rather than a page, because a row is all it needs. The last column is the one the ranking set has no equivalent of.
| Weed | Leaf and stem | Flower, height, where it grows | Most confused with |
|---|---|---|---|
| Chickweed | Small, soft, fresh-green leaves on weak sprawling stems that root wherever they touch soil. Never stands up on its own. | White starry flowers. The RHS puts it at up to 35cm, though it usually sits flat. Bare soil, borders, seed trays, path edges. | The mouse-ear chickweeds. If the plant is hairy all over rather than nearly smooth, you have a mouse-ear rather than common chickweed. |
| Hairy bittercress | A low rosette of small rounded leaflets, then a thin flower stem straight up out of the middle of it. | Tiny white flowers, to about 30cm. Pot plants, gravel, damp bare soil, and it gets going early in the year. | Other small white cresses, and chickweed while both are still rosettes. The seedpod settles it: the RHS calls them explosive, and a ripe plant fires seed at you when you brush it. |
| Broad-leaved and curled dock | Big coarse leaves off a stout stem, over a branched taproot. Broad-leaved dock has wide leaves; NatureSpot describes curled dock as narrow-lanceolate with very wavy margins. | Tall spikes of small pale flowers going rusty brown as seed ripens, June to October. Grassland, verges, neglected ground, path edges. | Japanese knotweed, genuinely. Dock is on the short list of plants people most often mistake for it, which is the one mix-up here with money attached. |
| Herb robert | Lacy, deeply divided foliage on stems that are often red-tinged. Crushed leaves have a strong musty smell. | Small pink flowers, to about 30cm. Walls, gravel, shady borders. Spreads by seed only. | The other cranesbills, cut-leaved cranesbill especially. Smell it. The RHS singles out that musty smell, and none of the others do it. |
| Sow thistle | Soft, jaggedly lobed leaves on a hollow stem that bleeds milky white sap when snapped. Garden Organic records considerable variation in leaf form, green in shade and reddish in the open. | Small dandelion-yellow heads, several to a branched plant, mainly June to August. Beds, allotments, waste ground, and it favours nutrient-rich soil. | Dandelion and real thistles. A dandelion carries one flower on one unbranched stalk; a sow thistle branches and carries many. It is not spiny, despite Garden Organic listing milk-thistle among its other names. |
| Greater and ribwort plantain | A flat rosette of leaves with strong parallel ribs running the length of each one. Ribwort keeps narrow strap leaves through spring and summer and broader ones in its overwintering rosette; greater plantain is the wide oval one. | A bare stalk carrying a short brown head. Garden Organic has ribwort flowering from April until the frosts. Lawns, path edges, anywhere feet compact the ground. | Each other, mostly. Garden Organic notes greater plantain is the more trampling-resistant of the two and the commoner one in lawns. Nothing else in a UK garden holds parallel ribs in a flat rosette like this. |
| Common field speedwell | A low sprawling annual. Garden Organic notes its stem pieces root readily in cool, damp conditions, which is how a hoeing session can move it about. | Small blue flowers on short stalks, and Garden Organic has it flowering throughout the year, with two generations in a season and seedling peaks in May and September. | The other speedwells, of which Garden Organic lists thyme-leaved, slender, ivy-leaved and wall. This is one of the rows below where I would go and look at a photograph. |
| Common mallow | Hairy plant with sprawling stems. NatureSpot describes the leaves as kidney-shaped to rounded-heart-shaped with three to seven shallow, rather rounded toothed lobes. | Pink to purple flowers 20 to 50mm across with darker veins, in clusters of two or more where leaf meets stem, June to September, to 1.5m. Verges, meadows, waste places. | The other mallows. The dark veins running out across a pink petal are the tell, along with lobes that are shallow and rounded rather than deeply cut. |
| Groundsel | Soft, irregularly lobed leaves. Garden Organic is blunt that plants have a very variable habit and leaf shape depending on how disturbed the ground is. | Small yellow flower clusters, usually with no visible petals, then white fluff. Main flowering April to October, and Garden Organic records a full life cycle in 5 to 6 weeks. Any disturbed ground, pots, allotments. | Ragwort, its taller relative, and that is the one confusion on this list with a real cost to an animal. See the note under the table. |
| Fat hen | Garden Organic calls it a very variable plant, weak and stunted on poor soil and tall and heavy on rich soil, so size and habit tell you nothing. Its other name, goosefoot, describes the leaf outline. | Dull green flower spikes, wind-pollinated, from July to September. Garden Organic has it especially plentiful in potatoes, sugar beet and root crops, and says manuring increases it. | The oraches, which are close relatives. Little rides on getting that one right either way. |
| Cleavers (goosegrass) | Whorls of narrow leaves at intervals up a weak scrambling stem. The whole plant grips clothing and anything else it touches, which is where sticky willy comes from. | Insignificant white flowers, scrambling to about 1m. Hedge bases and borders. The RHS notes it spreads by green bristly seeds, which hitch a lift on whatever brushes past. | Nothing much. Whorls of leaves plus a plant that sticks to your sleeve is cleavers and only cleavers. |
| Oxalis (yellow sorrel) | Clover-like leaves in threes, green or red-purple. That is the RHS description, and the resemblance to clover is the whole problem with it. | Small yellow or pink flowers. Paving joints, pots, borders. | Clover. The difference that matters is not the leaf, it is underneath: the RHS records oxalis spreading by explosive seed, by bulbils and by rooting stems, so pulling it hands it a lift to somewhere new. |
| Willowherb, including rosebay | NatureSpot describes broad-leaved willowherb as having a rounded stem with oval, usually toothed, very short-stalked leaves, opposite lower down and alternate above. Rosebay is the tall one. | Broad-leaved: purplish pink flowers 6 to 12mm with notched petals, May to August. Rosebay: deep pinkish-purple spires to 1.5m, spreading by surface roots and fluffy seed from long pods. Gravel, path edges, walls. | Each other, and their own hybrids. NatureSpot says willowherbs hybridise commonly and that reliable identification needs photographs showing the four-lobed stigma as well as the leaf. This is the genus where an app is likeliest to hand you a confident wrong answer. |
One row above has a consequence attached and it is the groundsel one. Groundsel and its taller relative ragwort get mixed up, and Garden Organic records that eating a large quantity of groundsel can cause liver damage in stock animals, with the alkaloids responsible surviving both drying and silage fermentation. Ragwort, meanwhile, is one of the five weeds named in the Weeds Act 1959. If you keep horses or livestock, or your clippings go anywhere near any, that pairing is worth being certain about. If you do not, it is a small yellow annual and you can pull it.
Four of those rows lean on habit and biology rather than on measured description, and I would rather name them than pretend the table is even. The authoritative UK sources I could reach gave excellent seed and habit data for sow thistle, common field speedwell, fat hen and greater plantain and very little on leaf and stem measurements. Fat hen is the honest edge case, because Garden Organic's own answer is that its size and shape change with soil fertility and crowding, so there is no fixed description to give you.
Where to look at an actual picture
There are no photographs here, and that is deliberate. This tells you when to stop reading and go and look at something else.
I do not have licensed photographs of these species, and I will not put computer-generated pictures of plants on an identification page. A generated image is plausible rather than accurate, and on this particular topic plausible-but-wrong has consequences: subtly wrong on giant hogweed and somebody gets burned, subtly wrong on knotweed and somebody answers a property form incorrectly. So this page does the thing it can do properly, which is written keys, and concedes the thing it cannot.
Where you genuinely need to see the plant, three places have real photographs and real botanical detail, and none of them are trying to sell you anything. Garden Organic's weed datasheets run to over a hundred individual species and are the best free source in the UK for how a weed actually behaves, which is where most of the seed and life-cycle figures on this page came from. NatureSpot carries per-species accounts with photographs and, usefully, is honest about which species are hard to tell apart. And the RHS list of common weeds covers twenty species with a short description of each, though it gives you no way to compare two of them side by side, which is the gap the table above is filling.
On giant hogweed in particular, do not work from a written description alone. Go and look at a photograph of a real one, from one of those sources or from your council's own invasive species page, before you get anywhere near a plant you suspect.
Group them by what is underneath, and the treatment answers itself
This is why identifying a weed is worth ten minutes. You are not learning a name, you are working out what is under the soil, because that is the only thing that decides what kills it.
| What it is underneath | Which of them | So what you do |
|---|---|---|
| Annuals that live and die on seed | Chickweed, hairy bittercress, groundsel, fat hen, common field speedwell, sow thistle, cleavers, herb robert | Hoe them or pull them, and do it before they set seed. A systemic weedkiller is overkill on a plant with no root worth reaching. The job is timing, not chemistry: Garden Organic puts groundsel at around 1,200 seeds a plant with a life cycle of 5 to 6 weeks, smooth sow-thistle at 5,000 to 40,000, speedwell at up to 7,000, and fat hen anywhere from 10 to 164,691 depending on the plant. |
| Perennials sitting on a taproot | Broad-leaved and curled dock, greater and ribwort plantain, common mallow | Snapping the top off achieves nothing, because the root regrows. Either get the whole taproot out with a fork, which works while the plant is young, or use a systemic that travels down inside it. Garden Organic has a large broad-leaved dock producing up to 60,000 ripe seeds a year and seed surviving over 50 years in undisturbed soil, so clearing one is only half the job. |
| Spreaders that multiply when you disturb them | Oxalis | This is the group where a tidy-up makes things worse. The RHS records oxalis spreading by bulbils and rooting stems as well as by explosive seed, so a fork through a patch is a distribution service. Treat it, or lift it whole and carefully, but do not rake it about. |
| Perennials that spread by root and by wind | Rosebay willowherb, and the smaller willowherbs | Two routes in, so blocking one does nothing. The RHS has rosebay spreading by surface roots and by fluffy seed from long pods, which means the plant in your gravel may have arrived on the breeze from three gardens away. Deal with what is in front of you and expect more arrivals. |
The dividing line running through that table is the same one running through this whole website. A contact treatment destroys the tissue it wets and travels nowhere, which is enough on an annual with nothing worth reaching underneath and useless on a taproot or a rhizome. A systemic is carried down inside the plant, which is the only way to reach the part that regrows. The systemic versus contact distinction is worked through properly on its own page, and it is the reason a correct identification saves you money rather than just satisfying curiosity.
One thing the seed figures in that table should change: your sense of what "getting on top of it" means. A single large dock can put 60,000 ripe seeds into the ground in a year, and Garden Organic records dock seed surviving over 50 years in undisturbed soil. Killing the plant is not the same as clearing the ground, which is why the same square metre keeps producing weeds long after you dealt with what was growing in it.
One family, four plants, four completely different consequences
The umbellifers get their own section because this is where an easy mix-up turns into a burn. Umbellifer means the flowers sit on spokes forming a flat plate, an umbel. From ten feet away, which is how far away most people identify a weed from, all four of these look broadly the same.
| Plant | Size and flower head | The tell | Cost of getting it wrong |
|---|---|---|---|
| Giant hogweed | Up to 5m, with white umbels up to 60cm across | Thick hollow ridged stem carrying stiff white bristles and scattered purple blotches, under huge deeply jagged leaves | Sap on skin plus sunlight causes severe burns and blistering. Getting this one wrong is an injury. |
| Common hogweed | Rarely over 2m, umbels around 20cm | Green hairy stem with far less pronounced blotching, and leaf lobes that are more rounded than jagged | A native plant most people walk past. It is in the same family though, so I would not strim it in shorts either. |
| Cow parsley | Waist to chest high, smaller flatter white umbels | Slender, green, softly hairy stem under finely divided lacy foliage, nothing like a hogweed leaf | Nothing. It is an ordinary native roadside plant. |
| Ground elder | 30 to 60cm, umbels only 2 to 6cm across | Hollow, grooved, hairless leaf stalks and leaves in groups of three toothed leaflets | You spend a season on the wrong treatment. A dinner plate is a hogweed, a coaster is ground elder. |
Size is the fastest thing to check and it does most of the work. If a hogweed-shaped plant looks oversized for a roadside verge, treat it as giant hogweed until you know otherwise and keep your distance rather than getting close enough to inspect the stem. Everything you need is on the giant hogweed page, including why cut material is still dangerous hours later.
At the other end of the same family, ground elder is the one where getting it wrong costs you a season rather than a hospital visit, because almost the whole plant lives below the soil and a fork through it multiplies the patch. How to get rid of ground elder covers that properly, including the identification detail that separates it from the other three here. And a warning that applies to all four: this is the plant family that contains the ones that will genuinely harm you, so never eat an umbellifer you are not completely certain of.
The weeds that already have a page of their own here
These are the ones where identification is only the start, because they resist being killed and each needs a different plan. A tell for each, then the page that deals with it.
- Horsetail and mare's tail. Nothing else in a UK garden looks like it: dark green whorls of narrow needles up a jointed stem, like a small fir tree or a bottle brush, and light brown fertile stems earlier in the year. It is a survivor with roots far deeper than anything else here, and it pushes up through driveways. Why it beats shop weedkiller and what actually works on it.
- Japanese knotweed. Shovel or heart-shaped leaves set alternately in a zigzag along hollow, bamboo-like canes flecked with purple, with creamy-white flower clusters in late summer. Look at the stem, not the leaf. How to identify Japanese knotweed and what it means for a sale.
- Giant hogweed. Huge deeply jagged leaves, a thick hollow stem with stiff white bristles and scattered purple blotches, flower heads up to 60cm across. What its sap does to skin, and why not to touch or strim it.
- Ivy. Woody, self-clinging and green right through winter, with the familiar lobed juvenile leaves changing to plain oval ones on mature flowering growth, which is why one plant can look like two. How to get rid of ivy without pulling your render off.
- Bindweed. Arrow or heart-shaped leaves on a thin stem that twines around anything within reach, with large white or pink trumpet flowers. Fleshy cream roots that snap and regrow. How to get rid of bindweed.
- Brambles. Arching thorny stems that root where the tip touches ground, so one plant walks across a garden. Why cutting them back sometimes backfires, and what to use instead.
- Stinging nettles. Coarse toothed leaves in opposite pairs, covered in stinging hairs, over a shallow mat of yellow creeping root. Dead-nettle looks similar and does not sting, which is the mix-up worth knowing. Why cutting a nettle patch back makes it worse.
- Ground elder. Leaves in groups of three toothed leaflets on hollow grooved hairless stalks, small white umbels 2 to 6cm across, and almost the entire plant below the soil. The two-season programme it actually needs.
- Bamboo. Woody jointed canes with papery sheaths at each joint, and the tell is not the plant at all: it is whether new canes are coming up away from the clump. A clumping bamboo stays where you put it, a running one sends rhizomes out sideways and under a fence. Why running or clumping decides the whole job.
- Couch grass. It is a grass, which is the whole difficulty, so look underneath rather than at the leaf: a dense mat of pale, pointed rhizomes running just below the surface. Above ground its spikelets sit flat against the stem, where a rye-grass turns its spikelets edge-on. Why rotavating it makes several plants out of one.
- Dandelion. A flat rosette of jagged leaves over a single thick taproot, with one flower per hollow leafless stem and milky sap in everything you break. Easy to name, and the naming is not the problem. Why it is back a fortnight after you pulled it.
If what you have is on that list, the name was the easy part. If it is on the table further up, the name was the whole job.
Two more have their own page for the opposite reason, because telling them apart IS the job. Creeping, spear and Scotch thistle separated matters because a spear thistle is a biennial you can finish with one cut before it seeds, while a creeping thistle is one root system throwing up a patch and pulling the tops is theatre. And common ragwort against its yellow look-alikes matters because the law that people think obliges them to pull it up names common ragwort specifically, so getting the species wrong means getting the duty wrong too.
One of those thirteen turns up in an Act of Parliament
The Weeds Act 1959 names five injurious weeds and no others: spear thistle, creeping or field thistle, curled dock, broad-leaved dock, and ragwort. Both docks are on it, which surprises people who think of a dock as the thing you rub on a nettle sting. It is agricultural legislation, aimed at land that grows crops or grazes stock rather than at a border, so a dock in your garden is not a legal problem and nobody is coming to look. What it does tell you is how much seed a dock puts about, which lines up with Garden Organic's figure of up to 60,000 ripe seeds from one large plant in a single year.
A separate list, Schedule 9 of the Wildlife and Countryside Act 1981, is the one that carries the offence of causing certain plants to spread into the wild. Japanese knotweed and giant hogweed are both on it. Nothing in the table above is, and nothing in the table above is notifiable, declarable on a property form, or of any interest to a mortgage lender. Ragwort is the only one of the thirteen with a legal shadow over it, and that is because of what it does to grazing animals. None of this is legal advice.
About this resource
I am The Weed Guy, one bloke who is qualified to spray professional weedkiller. This page is built on published botanical and horticultural sources rather than on any work of my own, and it says which is which. The seed counts, life cycles, habitats and the trampling and toxicity notes come from Garden Organic's weed datasheets. The leaf, flower and habit descriptions for common mallow, broad-leaved willowherb and curled dock come from NatureSpot species accounts. The short descriptions for chickweed, hairy bittercress, herb robert, cleavers, oxalis and rosebay willowherb come from the RHS list of common weeds. Google's wording about Lens is quoted from Google's own page for it, and the Visual Look Up article title is the one Apple uses in the iPhone user guide.
Where I could not verify something, it is not here. Apple's own article on Visual Look Up would not load, so there is no claim on this page about how accurately an iPhone identifies a plant. I have not ranked the paid plant-identification apps, because I have no source for their accuracy and a ranking without one would be invented. And I have said plainly which four rows in the table lean on habit rather than measured description, instead of padding them out to look even.
The knotweed and hogweed material here is identification and context only. I do not offer removal of either, and nothing on this page is a treatment plan, a legal opinion or a substitute for a specialist looking at the actual plant. This page carries no product links at all, because nothing you can buy identifies a plant for you, so there is nothing on it I earn from either way. The site's position on that is set out on the affiliate disclosure page.
Common questions
How do I figure out what weed I have?
Work from the stem and the leaf arrangement first, not the flower. Flowers are seasonal and half the plants in a garden are not carrying one when you look. Ask four things in order: is it upright or sprawling, are the leaves opposite each other or alternating up the stem, is the stem hollow or solid, and does it bleed anything when you snap it. That gets you to a shortlist faster than a picture search does. Then check the shortlist against the table on this page, and only then take a photo to an app to confirm. If your shortlist contains giant hogweed or Japanese knotweed, stop using the phone and read the pages on those two.
What is the app that identifies weeds by photo in the UK?
The one most people mean is Google Lens, and it is already on your phone rather than being something you download. Google's own page for it says Lens will "Identify plants and animals", and gives "Find out what plant is in your friend's apartment" as the example. On an iPhone there is also a built-in version in the Photos app called Visual Look Up, which Apple documents in the iPhone user guide under "Identify objects in your photos and videos". I am not going to rank the paid plant-ID apps for you, because I have no source for how accurate any of them actually are and I would only be guessing.
Is there a completely free plant identifier app?
Yes, and you almost certainly have two already. Google Lens is built into the Google app and into Chrome, and there is no subscription attached to it. On an iPhone, Visual Look Up sits inside the Photos app you already use. Between them that covers the question most people are really asking, which is whether they need to pay for something before they can find out what is growing in the gravel. They do not. What neither will do is tell you what the answer means, which is the part this page is for.
How do I use Google to identify a weed?
The camera icon in the Google search bar is Lens. Tap it, point the phone at the plant and it will search on what it sees rather than on words. Two things make a real difference to the answer you get back. Fill the frame with one part of the plant rather than photographing a whole flowerbed, because a wide shot of mixed planting gives it nothing to lock onto. And photograph the part that actually identifies the plant: for most of the weeds on this page that means the stem and the leaf join, not a pretty flower, because the flower is the bit lots of different species have in common.
Can my iPhone identify weeds?
It has the feature built in. Apple's iPhone user guide carries an article called "Identify objects in your photos and videos", which is the Visual Look Up feature in the Photos app. I have not been able to verify from Apple's own documentation how well it does on UK weed species specifically, so I am not going to tell you it is reliable or that it is not. Treat it the way you would treat any photo identification: fine as a starting point on something ordinary, not good enough on its own for anything where being wrong costs you money or skin.
Are the photo apps actually any good?
On a common plant in flower, photographed close up, they are good enough to save you an afternoon. Four things break them, and they are all worth knowing. Lookalikes that a picture cannot separate, like the willowherbs, where NatureSpot says even a botanist wants a photograph of the four-lobed stigma. Seedlings, which frequently look nothing like the adult plant. Variegated and coloured garden forms, which do not match the reference photos. And a photo of the wrong part of the plant, which is the commonest of the four by a distance. The honest summary is that an app is very good at telling you what a plant is called and no use at all at telling you what it is going to cost you.
How do I identify weeds in my garden in the UK?
Start by splitting them into three piles rather than trying to name all of them. Pile one is the soft annuals coming up in bare soil, which you can hoe without ever knowing their names. Pile two is the tougher perennials that keep returning to the same spot, where the name matters because it decides the treatment and the timing. Pile three is anything that makes you hesitate: unusually large, oddly blotched stems, bamboo-like canes, a zigzag growth pattern. Pile three is the only one worth being slow and careful about, and it is also the only one where I would not accept an app's answer.
Which UK weeds is it actually dangerous to get wrong?
Two, and for completely different reasons. Giant hogweed, because its sap combined with sunlight causes severe burns, so a wrong call there is a physical injury rather than a gardening mistake. And Japanese knotweed, because it affects mortgage lending, property sales and your legal position with a neighbour, so a wrong call there is a financial and legal problem. There is a third worth adding for anyone with livestock or horses nearby: ragwort, which is one of the five injurious weeds named in the Weeds Act 1959, and which people confuse with groundsel. Everything else on this page is a matter of tidiness and timing.
Why are there no photographs on this page?
Because I cannot show you a real one and I will not show you a fake one. Licensed photographs of every species here are not something this website has, and a computer-generated picture of a plant is exactly the wrong thing to put on an identification page: if it is subtly wrong on giant hogweed, somebody gets burned, and if it is subtly wrong on knotweed, somebody answers a property form incorrectly. So this page is built on written keys instead, and where you genuinely need to see the plant I send you somewhere that has a real photograph of it. That is a real limitation of this page, and pretending otherwise would be worse.
Is dock really named in an Act of Parliament?
It is. The Weeds Act 1959 names five injurious weeds, and two of them are docks: spear thistle, creeping or field thistle, curled dock, broad-leaved dock and ragwort is the whole list. That is agricultural legislation aimed at land that grows crops or grazes stock, not at a dock in a garden border, and nobody is going to knock on your gate about it. What it does tell you is how seriously a dock's seed output is taken, which lines up with Garden Organic's figure of up to 60,000 ripe seeds from one large plant in a year. None of this is legal advice.