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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Wednesday 6th July 2011

Two completely unrelated websites I visited today took me back to the subject of misunderstandings arising from using the wrong plant names.

I wrote last month Thursday 16th June 2011 about the tendency of American websites to call Solanum dulcamara ‘deadly nightshade’ when that name applies to Atropa belladonna. Solanum dulcamara being ‘bittersweet’ or ‘woody nightshade’. That previous entry has photos showing the very large differences in appearance between the two.

Well, today, because it gives a link to this site’s page about Rheum x hybridum, rhubarb, I found a webpage, created in February this year, with another one of those ‘Ten Most…’ lists that pop up around the web. This one was ‘10 Common But Deadly Plants’ so, at least, the author was avoiding any claim of hierarchical dominance for them. Having said that, they were numbered 1 to 10 so you might assume an order of merit.

In at No. 3, ‘Deadly Nightshade (Atropa Belladonna)' (sic). And underneath the heading a picture of Solanum dulcamara. The two paragraphs were about Atropa belladonna and the link at the end was to Wikipedia’s page about that plant, which has a number of correct photographs. So, how comes the author manages to write about the right plant and link to the correct plant but gets a photo of the wrong plant?

I started drafting this yesterday morning but when I revisited the page, later, to double check what had been written the picture had been changed to one of Atropa belladonna. It’s interesting that after five months of having the wrong photo it has been changed on the very day I was writing about it.

The other instance of what might be wrong-naming came in a newspaper report from Idaho. Under the headline ‘Poison hemlock endangers livestock, humans’ was a report detailing the problems caused to Idaho farmers because of cattle grazing on poison hemlock and the potential danger to humans. This report gave details of the effects of poisoning and quoted a prominent farmer and two experts on weeds. What it didn’t do, at any point, was give the botanical name of the plant being discussed.

The reason that is an important omission is because I don’t think the plant being discussed was poison hemlock. It was, almost certainly, hemlock that is poisonous but that doesn’t make it ‘poison hemlock’.

Conium maculatum is ‘poison hemlock’ and careful reading of the article gives a number of indications that this is not the plant being written about. That, it seems likely, is actually Cicuta virosa, water hemlock or cowbane.

There are a number of points in the piece that lead to my doubts. I’ll go through them, briefly, as they appear. I have a number of books detailing the effects of different plant poisons on farm animals but I’ve taken most of what follows from a UK Ministry of Agriculture, Fisheries and Food 1984 publication ‘Poisonous Plants in Britain and their effect on Animals and Man’.

‘It is so toxic that horses and cows literally can die within hours’. One key effect of Conium maculatum is that it is generally reported as being slow to act whereas for Cicuta virosa ‘Clinical signs appear within an hour of ingestion.’

Conium maculatum, poison hemlock

Conium maculatum, poison hemlock

‘"The roots are deadly," he said.’ With Conium maculatum the roots are the least poisonous part but for Cicuta virosa the yellow juice containing the poison is most concentrated in the roots.

‘Cattle like it…’ One of the key factors that helps with identification of Conium maculatum is the mouse like smell it emits if the plant is bruised or crushed. In my own experience, warm damp weather is enough to cause this smell to be given off without making any contact with the plant. But this unpleasant odour is a deterrent to consumption for humans and animals and most reported cases of Conium maculatum poisoning in animals occur when other grazing is unavailable and the animals are desperate for food.

‘Poison hemlock grows in riparian areas, along stream banks, canals and ditch banks’. As you might conclude from its common name ‘water hemlock’, Cicuta virosa is much more likely to be found in these areas whereas Conium maculatum can be found in just about any environment.

The confusion comes with the closing paragraphs of the piece. These give the correct growing habit for Conium maculatum and mention the purple blotches on the stalks, another of the key identifiers for this plant rather than the many other plants that bear some resemblance.

On balance, I think the various experts quoted in the article were referring to Cicuta virosa, water hemlock, but the author has added some details about Conium maculatum after, perhaps, looking up ‘poison hemlock’ online. But, I can’t be sure and an article intending to give a warning about a potential risk is of little value if the risk is not properly identified.

Just by using the correct botanical name, all confusion would have been removed.

Incidentally, Cicuta virosa is not a common plant in the UK. That’s why I don’t, at the moment, have a page on it. But, I think, I might add one particularly to deal with how to avoid overlap with other plants with ‘hemlock’ in their common names.