Plants that look and smell like parsnips but are highly poisonous and potentially deadly have been washed up on beaches in Cumbria after the recent stormy weather.

Coastguards have warned people to avoid the plants called hemlock water dropwort (Oenanthe crocata), which is also known as dead man’s fingers.

The coastguard rescue team based in Millom said they had received reports of the plant being washed up on local beaches.

“Even a small portion can prove fatal to humans by attacking the nervous system,” they said on their Facebook page. “It is also fatal to animals. The plant has a highly poisonous root that looks and smells like parsnip.

“It is highly likely that this is happening due to the aftermath of recent stormy weather. We advise people, especially with children and animals, to stay vigilant, avoid this plant and take extra care when visiting the beach.”

Hemlock water dropwort is one of Britain’s most poisonous indigenous plants. The roots, which look and smell like parnip, are poisonous. Eating it can cause nausea, vomiting, fever, seizures and hallucination.

Deaths have occurred but are far more common in animals than humans, said Geoff Dann, a foraging teacher and writer who is about to publish a new book on edible plants.

“It is known to kill livestock. Usually what happens is that it gets disturbed by the edge of a river by earthworks, or something, and the roots are exposed and are eaten by livestock.

“There are also cases of people digging it up and thinking it is a plant you can eat, like water parsnip or wild celery … but that is pretty rare.”

It is highly poisonous “but you’d have to eat a lot of it to die”, he said. “They are great big fat tubers, but who walks along a beach and picks up a random wild plant washed up on a beach and eats it? It seems a weird thing to do.”

Deaths are rare but the unpleasantness and dangers of the plant was highlighted by a report in the Emergency Medical Journal (EMJ) about eight young adults on holiday in Argyll.

They collected what they thought were water parsnips from a stream and made a curry. Ten hours later one of the group had a seizure and was taken to hospital. Others also became unwell and nauseous and a further person had be admitted to hospital after eating leftovers.

The EMJ report concluded: “It is possible that with increasing interest in ‘natural’ foods, accidental poisoning of this nature may become more frequent. These cases illustrate the potential dangers of this, but highlight the fact that even in small communities expertise is available and if accessed appropriately can be invaluable.”

Researchers in Italy have also written that hemlock water dropwort was used in pre-Roman Sardinia for the ritual killing of older people considered a burden.

The plant, it has been said, leaves corpses with what could be described as a sardonic grin.

Dann said the plant was not Britain’s most toxic. That accolade, he believes, should go to monkshood, or wolf’s bane. “There was a case a few years ago of a guy clearing it and he had a cut on his hand. The sap went in to the cut and it was enough to kill him.”