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Poisonous UK plants you might encounter when foraging, and exactly what they do to you…

Most folks know that there are dangerous plants to watch out for when foraging and, perhaps wisely, the fear of picking the wrong one prevents them from gathering their own food at all. The thing is however it’s all about recognition, when you can recognise your friends and you know what your enemies look like then you can be confident that what you bring home is simply nutrition-packed wild food that will only serve to strengthen your connection with the earth (and not the six feet deep in a box type of connection!).

You could say I have a fascination with poisonous plants as well as the edible types; there’s something about the idea that a human at the top of the food chain could be so easily put down by a plant that's humbling to say the least. OK, perhaps it’s indicative of a darker problem on my part but luckily for you it can be handy information so scroll down if you dare and meet some of the most powerful plants you might encounter in Britain whilst foraging and who refuse to be trifled with (a second time anyway!)... Tea anyone? ;)



Hemlock – Locked in...

Conium maculatum

Belonging to the Carrot family (Apiaceae or Umbelliferae) and the reason that this is the most difficult family of plants to safely identify - despite us being very familiar with it’s cultivated root cousin, gathering this family is not recommended to beginner foragers. Most of the unfortunate folks who have consumed it apparently did so after confusing it with common garden Parsley or Carrot. Some lived to tell the tale, though more were not so lucky.

All parts of the plant are toxic containing 5 alkaloids (nitrogenous organic compounds which have pronounced physiological actions on humans, eg Morphine): Coniine, Conhydrine, pseudoconhydrine, methyl-coniine and ethyl-piperidine.

Ingesting even a small quantity of Hemlock initially causes vomiting, though this apparently isn’t always the case, followed quickly by muscle paralysis and convulsions. Symptoms of paralysis begin as little as 15 minutes and, depending on the amount eaten and without medical intervention, death will surely follow up to several hours later.

What makes Hemlock particularly brutal is that this plant apparently kills from the outside in whilst having no effect on the brain or consciousness, meaning that as your limbs, lips, and lungs gradually become paralysed you’ll be ‘locked in’, unable to communicate or do anything about it yet very much aware the entire time!


Lily of the valley – Mary’s Tears

Convallaria majalis

Lily of the valleyTo the untrained eye the leaves of this plant could quite easily be confused with Wild Garlic before the flowers show, as could the bulbs it grows from, though both of course lack the signature onion/garlic smell that confirms a correct identification.

Lily of the Valley uses glycosides in it’s defence (a molecule in which a sugar is bound to another functional group via a glycosidic bond) containing 3; convallarin, convallamarin, and convallotoxin, as well as saponins known to cause gastrointestinal pain and upset.

Convallotoxtin affects the heart causing an irregular and slow rhythm, which in itself can be a scary experience. Other symptoms include lowered blood pressure, dizzyness, headaches, and confusion as well as the abdominal pain and upset mentioned above. It apparently requires you to eat quite a large quantity before realising your mistake and in most instances people have fully recovered so thankfully there are not many reported instances of fatal poisoning, though of course children, the elderly, and those with pre-existing heart problems would be at higher risk of its powerful effects.


Cuckoo pint – Willy Lily

Arum maculatum

Another woodland plant similar in appearance to Wild Garlic or Common Sorrel when young and with bizarre phallic-shaped flowers (explains the snigger-worthy common names!) later in their season.

The clusters of berries that poke up from the soil after the naughty looking flower fades generally scream suspicion and so are unlikely to be eaten, the roots and leaves might be more easily confused for other edibles though the pain and burning should quickly stop even the most curious of nibbling foragers!

Along with dangerous glycosides, Cuckoo Pint contains oxalates which are made up of microscopic needle shaped crystals which cause severe irritation and pain to the mouth, throat, and digestive tract if swallowed. High quantities of Oxalic acid is toxic causing serious liver and kidney damage.

Despite a surprisingly high number of reported incidences of poisoning, because of the immediate and intense reaction the mistake is quickly realised so a lethal dosage of Arum is generally not consumed. However the swelling caused by irritation to the mouth and throat can be dangerous enough in respect to the airway, and instances were the irritant has been introduced to the eye also warrant immediate hospital treatment.

Historic records reveal that the roots of Cuckoo Pint was once used as a vegetable due to it’s high starch content and I’m sure still is in some parts of the world, though it is only after careful processing and thorough cooking that the irritating oxalates are rendered safe enough for consumption. As intrigued as I am I think I’ll give it a miss for now! ;)


Wood Anemone – welcome to the horror show!

Anemone nemorosa

A pretty indicator of Ancient Woodland and the county flower of Middlesex. A part of the frankly unfriendly Buttercup family (Ranunculaceae), despite their beautiful appearance all Anemones are poisonous containing the dangerous irritant Protoanemonin which can cause painful blistering in contact with the skin or mucosa. 

Wood Anemone could be confused with Wood Sorrel due to it’s similar flower and habitat, though with very different leaves. The bitter flavour should put you off but if not you can look forward to further burning of the mouth, throat, and gastrointestinal irritation, before severe bouts of vomiting progressing further (through damage caused by repeated retching and irritation) to the vomiting of blood! Visual and mental disturbance is also reported as well as inflammation of the Liver which can go on to create lasting health problems.

It should take an extremely large quantity of the raw plant to cause actual death, though vomiting blood is enough of a horror show in my opinion to be classed as an extremely poisonous plant to beware of!


Giant Hogweedthe plant with an ASBO

Heracleum mantegazzianum

A plant doesn’t have to be eaten to get you into trouble, Giant Hogweed is a plant that’s made the rounds in news before and has even been dubbed ‘The most dangerous plant in Britain’ though that title is perhaps a little extreme! 

Hogweed burns develop slowly due to photosensitising furanocoumarins contained in the sap that are released from damaged leaves or stems so if you leave it be you should be just fine. In combination with UV light it goes on to develop a severe rash of extremely painful blisters akin to third degree burns, and can also go on to cause blindness if introduced to the eye. Permanent scarring is likely and repeating issues with the area may present in later years. Hogweed is a member of the Carrot family, like the deadly Hemlock, and in some instances gardeners have reported similar burns and rashes caused by other members of the family.

Severe damage to the skin like burns are extremely serious and if all that damage can happen from a simple brush in with the sap, an unlucky accident like falling into a patch of the plants could indeed prove fatal!

Common Hogweed (edible) Heracleum sphondylium is native to the UK but the Giant Hogweed is an introduced or ‘escaped’ ornamental species and due to it’s powerful action is in fact now illegal to grow whether you were aware of it’s presence or not meaning that the landowner could be subject to some hefty fines. It’s quite impressive though, what other plant can boast being subject to an Anti Social Behaviour Order?

Giant Hogweed really does grow to an extreme size with a stem of up to 5 inches in diameter and a height of over 4 metres, to put it into perspective pictured (right) is us parked next to a particularly impressive stand in Waki (who is not a small motor home!) of which I believe is actually the smaller and friendlier Common Hogweed. Wild Food UK have a handy comparison identification guide here to help you tell the two apart. In most cases of contact you can avoid issues by simply covering up, and if you do think you’ve been in contact with the sap by immediately and thoroughly washing the area with soap and water as well as staying out of strong sunlight for a few days. Unfortunately it’s delayed onset means that you might not always be aware that you’ve been in contact until it’s already too late!


Yellow Iris – burning flag

Iris pseudacorus

Without the spectacular flowers present the poisonous Iris or Yellow Flagcould be mistaken for the highly nutritious Reed Mace, which doesn’t have the mid rib along the centre of its leaves prominent in Iris.

Like the others, you should realise your mistake once the pain and burning set in causing excessive salivation, with vomiting and abdominal pain no doubt soon to follow – all symptoms of the highly irritating Iridin contained in the juice and concentrated in the root rhizome, which can also cause contact burns to the skin. According to autopsies on poisoned animals have shown consistent evidence of multiple critical internal organs being affected, including the kidneys and liver.

If a large enough quantity was to be consumed or if you were perhaps without medical assistance the painful irritation would continue throughout the digestive tract causing intestinal bleeding and finally death, though let’s face it we’re ever really that far away from a hospital in the UK so you should be OK.


Scarlet Pimpernel – seek him not!

Anagallis arvensis

Also found as a blue variety, without flowers the Pimpernel looks a lot like Chickweed and, as is often the case, grows in many of the same places meaning that an instance of confusion is quite likely. Pimpernel roots contain several glycosides including cyclamin, and the herb and seeds contain saponins which cause gastrointestinal upset (so more of the happy diarrhoea, vomiting, and abdominal cramps). The plant is reported to also have a strong haemolytic effect, meaning the rupture and collapse of red blood cells - which frankly sounds horrific to say the least!

Pimpernel is listed as being poisonous to both humans and animals though in reality there are not many reported instances of poisoning for either and little is known about how dangerous it really is. From what little information I could find on it it seems that interestingly the amount of rainfall can go on to affect just how mean this little plant can be, ranging from virtually nothing to being fatally toxic. It’s reported to be extremely bitter and likely to cause a burning sensation in the mouth so in all likelihood the mistake is realised before taken too far. Still, one to watch out for if you’re new to gathering wild Chickweed as an edible.


Deadly Nightshade – Beautiful lady

Atropa belladonna

artwork by Britt WilsonCredit for this beautiful artwork goes to the talented Britt Wilson, prints available for purchase. 

There are other members of the Nightshade family and most often you’re likely to find it’s equally toxic brightly purple-flowered cousin Bittersweet or Woody Nightshade Solanum dulcamara. You may also be consuming other members of the family on a daily basis without realising; namely potatoes and tomatoes!

Deadly Nightshade is a small vine with green-plum coloured bell shaped flowers and sporting attractive black berries within a single star shaped cup that often winds its way throughout blackberry bushes and other edible shrubs and so could quite easily be mixed-up if the gatherer is not paying close attention to exactly what they are picking from. According to those who have tried the berries and survived they’re not unpleasant and so explains why there are so many cases of folks, mainly children, having eaten quite a few unlike other plants in which the burning gives fair warning that a mistake has been made. The berries of Bittersweet nightshade are, as the name suggests, bitter and so associated in far less instances of poisoning – they are however often displayed in a variety of colours depending on the stage of ripeness and so may imitate a wider range of edible berries throughout its life cycle.

Belladonna contains a dangerous cocktail of tropane alkaloids including atropine, scopolamine and hyoscyamine as well as a-solanine which is the poison present in greened potatoes (the eating of which we are aware is not recommended!).

It can take up to 2 days for the effects of Nightshade to present which can pose problems for identifying the cause of the persons illness. It’s poisoning effects are among some of the more spectacular causing vivid hallucinations and in some instances a kind of painful internal irritation and necrosis of the skin similar to cellulitis. Extreme thirst is one of the first reported symptoms to present, followed by blurred vision and drowsiness, slurred speech, a high heart rate and increasing agitation, finally progressing to full blown delirium and convulsions. Death is preceded by coma. Dilation of the pupils is an obvious symptom to check for along with a sensitivity to light.

The quantity of Nightshade to constitute a lethal dose is subject to debate since some people have apparently survived eating 20 or so of the berries and other unfortunate souls have died after only half of one. It seems perhaps that the environment may have an influence on the level of toxicity much like the level of rainfall affects the toxicity of Pimpernel.


White Briony – the ‘dangerously powerful’ laxative!

Bryonia dioica

Britain's only native member of the Cucumber family, the attractive White Briony vine might be confused for Honeysuckle or other berry producing plants and trees, especially if using that plant as a support to climb.

White Briony combines the glycoside bryonin and the alkoloid bryonicine, creating what is labelled a ‘dangerously powerful’ laxative, and causing abdominal pain, vomiting, and also excessive urination. Severe dehydration then is likely to be a serious hazard in a run in with this plant.

The berries smell unpleasant, containing a juice described as nauseating so it’s unlikely that anyone should successfully consume enough to do themselves any lasting damage, horses and dogs are apparently most commonly the ones to suffer fatal poisoning. The root however has a greater concentration of the chemicals and consumption of a large amount will result in an elevated heart rate, convulsions, lack of muscle control, stupor and nervous excitement, opisthotonos (rigid muscle tension), and finally death within a number of hours.


What should you do if you think you or someone has eaten a poisonous plant?

Since some of these plants can kill in a matter of hours you need to get medical help as soon as possible but there are some things you can do to improve your chances:

  • If you can identify or at least safely bag a sample of the plant responsible and be sure to tell the dispatcher and paramedics/doctor what it is as soon as possible – this will enable them to get on to the correct treatment without delay.

  • While you await help, if the person is fully conscious and able to do so, encourage them to take activated charcoal – either as whole tablets or crushed and mixed with water. Not just any old charcoal from the BBQ though! Activated charcoal is specifically designed for human consumption and it’s porous nature means it helps to attract and capture molecules of poison meaning that much less will be absorbed through the digestive tract to cause further problems. NOTE! If the person is suffering any kind of restriction to the airway do not attempt to make them eat or drink anything as it may end up blocking the airway completely which is a much more serious and immediate problem!

  • As also in cases of chemical poisoning, and as chilli lovers will  already be well aware of, drinking milk can help to soothe sensations of burning and pain to the mouth and throat.

  • If the problem is a chemical burn to the skin or eye, soothe the area with plenty of cold running water - making sure not to allow the water and any contaminants onto the other eye or healthy areas of skin.


So I'm sure that by now I've sufficiently terrified you, and perhaps even scared you off of the idea of foraging food altogether! That isn't my intention so I apologise if I have, rather I just want you all to be safe whilst enjoying the bounty of nature. The reality is that for the few examples above I searched a 500+ page identification book mostly full of beautiful and helpful plants and there are very few reported instances of poisoning by wild plants as displayed in this report on Swiss cases

There are of course other poisonous plants of note in the UK, though not many that are as likely to be confused with anything edible as like the ones above, and let’s face it even they are a bit of a stretch to take too far.


With thanks to and for their extensive knowledge base on the history, actual poisoning incidences, and chemical make-up of these fantastic wild plants. 


What did you think of this article? Have you ever had a personal run in or a close call with a poisonous plant? We’d love to hear from you so leave us a comment in the section below!


Sarah is an artist and writer with a lifetime interest in camping and survival techniques.

Living the #vanlife since before it was a hashtag and touring on two wheels with her husband Ryan, they have a wealth of camping and motorcycling knowledge to share, and know a thing or two about packing light! read more

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