Oct 31 2020

It wont go bump in the night but they can harm us…

It might not go bump in the night but there are definitely things in the woods that can cause us serious harm and as conservation volunteers and staff we need to be aware of the dangers.


This Poisonous plants guidance is designed to draw attention to toxic plants that are often encountered while working on conservation tasks – it is not exhaustive, and there are other toxic plants within our countryside that are not covered here. As beautiful as they are some of these are dangerous and should be respected.


The plants detailed below, however, can pose a significant risk to people working with them – this document highlights those risks, and suggests precautions.


Anyone who feels ill or shows signs of allergic reaction after working with unidentified plants should contact their GP immediately or attend an NHS walk in centre.


Bracken – Pteridium aquilinum

Associated dangers:

Bracken contains a carcinogen (Ptaquiloside) linked with oesophageal and stomach cancer in mammals.

Bracken Spores (released between July & September) are an irritant to throat/lungs

People who have spent all their lives living amongst bracken and breathing in the spores may be at higher risk of getting some cancers.

Danger to general population and to casual visitors in bracken-infested areas is negligible.


Wash hands after handling bracken, before eating, drinking or smoking.

Avoid mechanically removing bracken (brush cutters or flails) during summer months

Anyone driving through bracken in a way that may disturb spores – on an ATV for example, is advised to wear a face mask that meets the requirements of EN:149


Deadly nightshade – Atropa belladonna

Associated dangers:

Symptoms of nightshade poisoning may be slow to appear but last for several days.

They include dryness in the mouth, thirst, difficulty in swallowing and speaking, blurred vision from the dilated pupils, vomiting, excessive stimulation of the heart, drowsiness and slurred speech.

Coma and convulsions often precede death.

All parts of the plant are toxic; however the greatest toxicity levels are contained within the roots

Children have been victims of poisoning in the past due to the attractive colour of the berries.


Wear waterproof gauntlets while handling nightshade, and wash hands immediately upon finishing the work – and before eating, drinking or smoking.

On sites where nightshade may be present, children must be closely supervised at all times.


Foxglove – Digitalis purpurea

Associated dangers:

Ingestion causes vomiting and diarrhoea.

Digitalis is also capable of affecting the heart to an extent that may cause heart failure.

Contact can also cause irritation to the skin.


Wear waterproof gloves if handling foxgloves, and avoid getting them near your face.

Wash hands thoroughly before eating, drinking or smoking.

If present, supervise children carefully to prevent them picking the colourful flowers.


Giant Hog Weed – Heracleum mantegazzianum

Associated dangers:

The sap of Giant Hogweed contains furanocoumarins. When these come into contact with the skin, in the presence of sunlight, they cause a condition called phytophotodermatitis – (a reddening of the skin, often followed by severe burns and blistering.)

The burns can last for several months and even once they have died down the skin can remain sensitive to light for many years.


Avoid the mechanical destruction of Hog Weed (flails or brush cutters for example) – this will spread large quantities of sap.

Do not touch the plant with bare skin – wear waterproof gauntlets.

Do not touch your bare skin with sap covered gloves.

Prevent UV sunlight from reaching skin by wearing long sleeves and trousers.

Apply sun block before beginning to work

If clothing may be contaminated with sap, remove it as soon as possible and launder it immediately.

Wash equipment with water immediately after use


Hemlock – Conium maculatum

Associated dangers:

Hemlock sap contains a violent emetic and convulsive (Coniine), which causes paralysis of the central and peripheral nervous system.

Death is usually the result of respiratory failure.

Maintenance workers have become ill, and required hospital treatment after cutting Hemlock with a Brushcutter.

The most easily- identifiable feature are the purple spots or blotches on the stem. These are unique to hemlock (maculatum means “spotted”). However, if you are in any doubt, please seek advice from an Ecologist.


Where possible, Avoid the mechanical cutting of Hemlock or other activities that could spread plant sap during the peak growing season – June & July.

Hand pulling or the use of selective herbicides is preferable.

If you have to touch Hemlock wear long, sturdy, waterproof gauntlets

Where mechanical cutting must occur, workers should wear solid polycarbonate visors that meet EN 166 and EN 352

Wash any tools used to clear the plant, carefully, after use.

Wash hands before eating, drinking and smoking.


Lords and ladies (Cuckoo Pint) – Arum maculatum

Associated dangers:

Can irritate the skin, mouth, tongue, and throat, resulting in throat swelling, breathing difficulties, burning pain, and stomach upset.

The bright berries are particularly attractive to children.


Wash hands after handling, and before eating drinking or smoking.

Where children are present, they must be closely supervised, especially when berries are present.

Laburnum – Laburnum anagyroides

Associated dangers:

Laburnum will most often be found on the borders of Trust property or in adjoining gardens.

All parts of the tree are poisonous: roots, bark, wood, leaves, flower-buds, petals, and seedpods. The most harmful part of the plant is the seedpods – these are sometimes mistaken, by children, for peapods (usually after they have been shown how to eat fresh raw peas straight from the plant in the vegetable garden.

Ingesting a small number of seeds will not usually cause problems – eating larger amounts, however causes vomiting, intense sleepiness, convulsive possibly tetanic movements, coma, slight frothing at the mouth and unequally dilated pupils


Wear gloves when handling cut Laburnum, and wash hands before eating, drinking or smoking.

If cutting dry wood, do so in a well-ventilated area and wear a dust mask that meets the requirements of EN:149

When seedpods are present ensure any children are closely supervised


Ragwort – Senecio jacobaea

Associated dangers:

Ragwort is extremely toxic to livestock such as horses or cattle, and under the 1959 Weeds Act it is an offence to allow it to spread to agricultural land.

Ragwort is less toxic to humans, but its sap is a strong allergen that can cause severe dermatitis.

Ragwort pollen is particularly unpleasant for those that suffer from hay fever.


When handling ragwort plants (fresh and dried) wear Sturdy waterproof gloves.

Keep arms and legs covered to prevent ragwort plants coming into contact with the skin.

Wear a facemask that complies with EN: 149 to avoid the inhalation of ragwort pollen.


Laurels – Prunus laurocerasus/ P lusitantica

Associated dangers:

The leaves and fruit pips contain cyanolipids that are capable of releasing cyanide and benzaldehyde.

The latter has the characteristic almond smell.

Crushing or otherwise macerating the leaves or fruit will produce low levels of hydrogen cyanide.

In a confined space such as a vehicle this could cause symptoms such as nausea and light headedness.

Burning Laurel leaves will release hydrogen cyanide within the smoke.

Ingesting laurel sap will cause severe respiratory problems.


Avoid crushing or burning laurel leaves or fruit pips and exercise caution if chipping it.

If transporting laurel, ensure the vehicle is well ventilated

After handling laurel, wash hands before eating drinking or smoking.

Supervise children carefully, to prevent the ingestion of fruit.


Monkshood – Aconitum Napellus

Associated dangers:

All parts of Monkshood are highly toxic, including the roots.

Ingestion of even a small amount results in severe gastrointestinal upset and possible heart failure.

The poison may also be administered by absorption through the skin or open wounds.

There are reports of people being unwell after smelling the flowers.


Avoid touching Monkshood with bare hands – if working in close proximity to it, cover any cuts or grazes with a waterproof plaster.

If it must be handled, wear sturdy waterproof gauntlets.

Do not control Monkshood with power or hand tools – if control is needed use a selective herbicide.

Wash hands carefully following contact with plant.


Water Dropwort – Oenanthe crocata

Associated dangers:

This plant is one of the most poisonous in Britain.

It is hairless with parsley-like leaves and occurs on the banks of streams, rivers, canals, lakes and ponds, roadside culverts, marshes and wet woodland.

It contains oenanthetoxin, a poly-unsaturated alcohol.

The roots contain the greatest concentration of toxin.

Ingesting even a small amount of raw plant material may be fatal

Symptoms include nausea, convulsions, excessive salivation, dilated pupils and respiratory failure.


Avoid working with or touching water dropwort wherever possible.

It has been confused with a number of harmless plants with a similar appearance. Therefore if you are unsure as to identification, stop work and seek advice from an Ecologist.

If it needs to be controlled or removed do so by hand, carefully, while wearing sturdy waterproof gauntlets.

Cover any cuts with a waterproof plaster before starting work.

Wash gloves and hands carefully after the work is complete, and before eating drinking or smoking.=

Supervise children carefully if present.


Common Yew – Taxus Baccata

Associated dangers:

Almost all parts of a Yew tree are toxic.

Where Yew berries have been ingested, there may be no symptoms; however death may follow within a few hours.

If symptoms do occur, they include trembling, staggering, coldness, weak pulse and collapse.

Poisoning can occur with as few as three berries.

Yew is one of the plants where the poison is not destroyed when the plant dies. Thus, branches removed from a yew by high winds or pruning will retain their poison.

Yew sap is an irritant, and Yew wood dust may cause respiratory distress.

Male Yew tree pollen is extremely allergenic, and can cause severe reactions during the months of March & April.


Wear gloves when handling cut Yew, and wash hands before eating, drinking or smoking.

If cutting dry Yew, do so in a well-ventilated area and wear a dust mask that meets the requirements of EN:149

Avoid chipping yew.

Hay fever sufferers should avoid working near Yew during March & April.


This guide can also be downloaded from the Library here:

Have you found this guidance useful? Please let us know. We’d like to create more guidance notes to help you, if you have any suggestions on subject matter please get in touch by commenting below.

Sarah Shaw – Volunteering Journey Officer – National Volunteering Team

1 Comment
  • Ken Miller

    This article is so important. Unfortunately some of these hazards from these plants are not well known to the general public. I know this from my own personal experience earlier this summer. I must point out immediately that what I describe below is NOTHING to do with any Woodland Trust activity or site. I have only recently renewed my membership after a lapse of many years, and I have just become a Voluntary Warden of several of my local woods.

    In the middle of the summer I went for several walks with a friend along a local canal and river. Both of us have an interest in foraging, or hunting for edible plants. We came across many clumps of what my friend said was Wild Celery, and she tried a small mouthful, and she aimed to return to collect enough to eat.

    Luckily when I returned home I realised that these clumps were what my book described as Hemlock Water Dropwort, and that it is the most poisonous plant in Britain. I have spent my life exploring outdoors, but I was shocked at my lack of knowledge of this plant.

    Luckily my friend suffered no consequences, and we have avoided this plant ever since.

    All I can say is we must all be careful, and in particular not eat anything that has not been properly identified.

    We should take considerable notice of this article, and pass this information on to our outdoor friends.

    November 8, 2020 at 3:23 pm

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