Here are some of the most poisonous plants you could encounter on a woodland walk. Find out what makes them toxic and how to recognise them.
Don't be alarmed, just take care and don't touch them. These species are a vital part of the ecosystem and many are a food source for insects.
Poison hemlock (Conium maculatum)
Hemlock is sometimes confused with other species in the Apiaceae family such as cow parsley. It’s a large plant up to 2m tall, with hollow, purple-blotched stems. The mature plants have an unpleasant smell apparently similar to mouse urine. You’ll find it in damp areas along the edges of woodland, along ditches, streams and roadside verges.
Hemlock contains several toxic alkaloids including coniine and is poisonous to humans and livestock. Consumption of just a small amount of any part of the plant can cause respiratory paralysis and death.
Foxglove (Digitalis purpurea)
You'll see this familiar woodland plant, with its tall spikes of pink and purple flowers, in early summer. It grows throughout the UK, along woodland edges, roadside verges, hedgerows and in gardens.
Foxgloves contain toxic cardiac glycosides. Ingestion of any parts of the plant (and often the leaves usually as a result of misidentification for comfrey, Symphytum officinale) can result in severe poisoning. Symptoms include nausea, headache, skin irritation and diarrhoea. In severe cases it can lead to visual and perceptual disturbances and heart and kidney problems.
The cardiac glycosides from foxglove have been used medicinally to make a heart stimulant drug. Foxgloves have also widely been used in folk medicine.
Lords and ladies (Arum maculatum)
Also known as cuckoo pint, you’ll find this plant in woodland and along hedgerows. It has large, arrow-shaped, purple-spotted leaves at the base of the plant. Its inflorescence has a yellow-green hood (technically known as a spathe) surrounding the flower spike (spadix). Its berries are green, orange or red, depending on their ripeness.
Take care when handling this plant. All parts of it can cause allergic reactions, but the berries are particularly poisonous. The plant contains minute needle-shaped crystals which can severely irritate the skin. Consumption of the plant can lead to throat swelling, breathing difficulties and stomach irritation. It’s to accidentally consume large quantities of this plant because it has an acrid taste and gives a tingling sensation which acts as a warning.
Deadly nightshade (Atropa belladonna)
You’ve probably heard of deadly nightshade and its dangerous reputation. It has purple-green, bell-shaped flowers and untoothed, oval leaves. The berries are green and they ripen to black. You’ll find it mainly in the southern half of the UK in woodland, along paths and in scrubby areas.
All parts of the plant are toxic, but the berries are especially poisonous. They contain a mixture of tropane alkaloids that affect the nervous system. Atropine, in particular, causes severe symptoms in humans, including sweating, vomiting, breathing difficulties, confusion, hallucinations and potential coma and death. It also has a pupil-widening effect that was known in ancient Greece. An extract of 'belladonna' (Italian for 'beautiful woman') was applied by women to enlarge their pupils.
Monkshood (Aconitum napellus)
Also known as Adam and Eve or devil’s helmet, this is one of the UK’s most poisonous plants. It’s widely naturalised, but may be native in damp woodlands, meadows and along ditches in the southern half of the UK.
Its attractive hooded, blue flowers have made it a popular garden plant and you’ll find cultivars in varying colours including pink, yellow and white. Its flowers grow on tall spikes that bloom between June and September.
All parts of the plant are poisonous, particularly the roots. If ingested, it can cause stomach and dizziness. The poison also affects the heart and in large amounts can be fatal, but poisonings are rare as it has such an unpleasant flavour. Toxins can even transfer to the skin via cuts, so it is important to always wear gloves when handling plants in your garden.
Several species of Aconitum have been used as arrow poisons. They have been used in the Aleutian Islands in Alaska to poison harpoon tips used in whaling.
Advice in case of accidental poisoning
If you think a child or adult has eaten part of a suspect plant, seek medical advice immediately from a hospital accident & emergency department.
Take a sample of the plant with you (as many parts of the plant as you can for accurate identification e.g. leaves, flowers, fruits, stem).
Do not panic and do not try to make the person sick.
In the case of animals, seek veterinary advice if you think an animal has eaten a poisonous plant. Take along samples of the plant.