Hemlock Water Dropwort

An interesting appearance a few weeks ago after some ditch clearance locally is Hemlock water dropwort (oenanthe crocata). Appearing to passers-by as just another clump of bright green spring growth this is in fact one of Britain’s most toxic plants (if not the most toxic).

Cattle are commonly killed by the plant after it’s uprooted in ditch clearances like this one. The roots are known as dead men’s fingers and are apparently quite tasty and very agreeable to cattle. The roots are the most toxic part year-round with the young leaves coming a close second.

As well as cattle this plant is regularly responsible for poisoning in humans. This most commonly occurs after mistaken identification, with the roots mistaken for wild parsnip, and the leaves and stems for wild celery.

There’s also a recorded case of someone just fancying a “bit of garnish for their sandwiches”. Bad choice!! Hemlock water dropwort poisoning can be fatal, depending on the quantity eaten and whether it’s been cooked. Even if not fatal an unpleasant few days in the hospital usually follows.

This plant is one of the major reasons people are nervous about eating umbellifers. Any plant family with an enormously toxic member needs to be treated with caution and, as always, unless you can 100% positively identify what you’re about to eat and know it’s edible, DON’T!

This extract from the Emergency Medical Journal (2002;19:472–473) gives a flavor of a typical case of hemlock water dropwort poisoning and the aftermath:

A group of eight young adults who were on holiday in Argyll collected what they thought were water parsnips from a small stream. The roots were cleaned, chopped, and added to a curry. All consumed the curry, but the majority of the group only had a small amount of the root, which was easily identifiable in the curry, partly because there was some doubt regarding its nature and partly because of its bitter taste.

Early the next morning, 10 hours after ingestion one of the group had a witnessed grand mal seizure lasting about five minutes. He was taken to the community hospital and was in a post-ictal state. No connection at this point was made with the ingestion of the plant root the night before.

Gradually over the course of the next four hours, a number of the group became unwell and nauseated. During this time four of the group consumed the leftovers for lunch. One of these individuals, subsequently become increasingly unwell, nauseated, and began to vomit.

He had a witnessed grand mal seizure lasting about three minutes. On arrival at the emergency department, this person was conscious but vomiting and experiencing visual hallucinations. The patient was agitated and tachycardic, but blood pressure and oxygen saturation were within normal limits.

He was hyper-reflexive with dilated pupils, but there were no focal neurological signs. He had one further grand mal seizure controlled with intravenous diazemuls.

The other patients all had varying degrees of nausea, vomiting, lethargy, sweating, and low-grade fever. Initially, it was uncertain from the description as to the identity of the poisonous plant.

The community hospital that they were admitted to serves a rural area of Argyll. The police were able to take an asymptomatic member of the group to the stream to recover a further plant. The police knew of a local botanist in the area who was able to positively identify the specimen.

Four of the group required admission to the hospital. The person who had required intravenous diazemules was observed over the next 48 hours. Biochemical and hematological parameters were all within normal limits, and his symptoms settled rapidly. The other three were discharged after 24 hours.

This episode highlighted some difficulties that can relate to plant poisoning. In this case, the cause of the poisoning was not readily apparent, but with the assistance of the local police, we were able to locate a plant specimen and use a local botanist to aid identification.

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.