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)
Although hemlock is sometimes confused with other species it can be identified in being a large plant, usually up to 2m tall, with a hollow stem with purple blotches on. Mature plants have an unpleasant smell apparently similar to mouse urine. You’ll find it in damp areas along the edges of woodland where the ground has been disturbed, as well as along ditches, streams and roadside verges.
The poison from this plant is famous for being that which Socrates drank. It contains several toxic alkaloids including coniine. This compound is poisonous to humans and livestock and consumption of just a small amount of any part of the plant can cause respiratory paralysis and death.
Foxglove (Digitalis purpurea)
This tall plant with its tube-shaped pink and purple flowers, which grow on a spike, is easily recognisable. You’ll find it throughout the UK along woodland edges, roadside verges, hedgerows and in gardens.
Foxglove contains 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, headaches, skin irritation and diarrhoea and in severe cases visual and perceptual disturbances and heart and kidney problems.
The plant is a source of digitoxin, a compound used in the heart stimulant drug digitalis. They have also widely been used in folk medicine.
Foxgloves are a beautiful plant, and very valuable for bees, so no need to worry but just be careful if you have them in your garden.
Lords and ladies (Arum maculatum)
Also known as cuckoo pint, this plant can be found in woodland and along the edge of hedgerows. It has large, purple-spotted basal leaves which are arrow shaped; a yellow-green hood structure, which appears to hide the flower spike, and berries which can be green, orange or red.
The berries of this plant are particularly poisonous. They contain oxalates of saponins which have needle-shaped crystals which irritate the skin, mouth, tongue, and throat. This results in swelling of throat, difficulty breathing, burning pain, and upset stomach. However, the acrid taste and tingling sensation when consumed mean that large amounts are rarely taken.
All parts of the plant can cause allergic reactions so care must be taken when handling it.
Deadly nightshade (Atropa belladonna)
Deadly nightshade is one of the most notorious poisonous plants. Its flower is bell-shaped and a purple-green colour. The leaves are untoothed and oval in shape. The berries are green, ripening 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 potent mixture of tropane alkaloids that interfere with the nervous system. Atropine in particular causes severe symptoms in humans, including sweating, vomiting, breathing difficulties, confusion, hallucinations and possible 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 attractive perennial plant has blue, purple, white, yellow or pink flowers that grow on a tall spike and deeply divided leaves. It’s found in the southern half of the UK in damp woodlands, meadows and along ditches. It flowers from June to September.
The entire plant is poisonous, particularly the roots. Poisons from this plant can transfer to the skin via cuts, so it is important to always wear gloves when handling plants in your garden. If ingested, you are likely to suffer an upset 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.
Several species of Aconitum have been used as arrow poisons. They were once used in Alaska's Aleutian Islands 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.