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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Monday 14th November 2011

From time to time, a web page will appear giving a one page take on the subject of poisonous plants in the garden. Many times these are in the form of a list. There are quite a number of websites devoted to ‘Top 10s’ of all sorts. There may even be a website giving a top 10 of ‘Top 10’ websites. At the risk of sounding as though I am sneering, I have to say that many such lists are flawed, often using the wrong photograph to identify a plant or repeating erroneous opinions about the nature of a particular plant.

At other times, what appears is the online version of a newspaper article where the paper’s gardening correspondent has decided to ‘do’ poisonous plants for this week’s column. These tend to be based on a much greater general gardening knowledge but can still contain some odd views.

Then there are the new breed of online publications falling somewhere between the two. The content never appears in hard copy but there is some form of editorial intervention to raise the standard of what’s published.

Helleborus, hellebore

Helleborus, hellebore

It was in one of these that I read a piece entitled ‘The poisoner’s garden’ that appeared at the end of October. What sent me back to it was the subject of fashion in poisons that I mentioned when I wrote about cases of Prunus laurocerasus poisoning in the 18th century.

The author doesn’t rank the plants she discusses but the choice of plants does interest me. Both Convallaria majalis, lily of the valley, and Daphne mezereum (or mezereon), spurge olive, often appear in these sort of pieces but I can’t see how they merit inclusion alongside such plants as Digitalis spp. or Helleborus or Taxus baccata.

Convallaria majalis contains alkaloids similar to those found in foxgloves and is, theoretically, deadly. But there are only a handful of references to it in the literature where reports of cases of poisoning arising from Digitalis are easy to find.

Daphne mezereum is a plant that most people seem to know as poisonous and seem to think is dangerous but there are only two references to it in the ‘International Poisonous Plants Checklist’. One of these is to a case from 1887 and the other is a mention in a report, published in 1996, about poisoning in children in Finland.

Solanum dulcamara, woody nightshade

Solanum dulcamara, woody nightshade

That work, ‘Plant Poisonings in children’ by A Lamminpää, and M Kinos from the University of Helsinki, looked at 71 cases, over a five year period, seen by two hospitals in Helsinki and 105 calls to the Finish Poison Information Centre over a six month period. It found that, of the 71 hospital cases, only 8 were confirmed poisonings presumably indicating that no symptoms were seen in the other cases but whether that was because there had been no poisoning or because timely treatment had prevented the emergence of symptoms is impossible to determine.

This report says that Convallaria majalis, Dieffenbachia spp. (dumb cane) and Cotoneaster spp. are the most frequent causes of plant poisoning but that Daphne mezereum, Symphoricarpos albus (snowberry), Cotoneaster spp., Lonicera spp. (honeysuckle) and Solanum dulcamara (woody nightshade) caused the most severe symptoms.

Now, I appreciate that this is only one report and that its conclusions about the plants to be most wary of are very different from the Swiss report discussed on this site but, as I said, it is the only modern reference I can find to Daphne mezereum poisoning. It is possible that attitudes towards this plant are shaped by this one document.

I want to stress that I’m using ‘The poisoner’s garden’ as an example rather than picking on it specifically. But it does reflect what other people write or say about poisonous plants by making much of Daphne but without any mention of snowberry, cotoneaster or honeysuckle all of which would seem to rank alongside it. It certainly makes me think there are fashions in poisonous plants.