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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Friday 28th October 2011

The church hall where I gave last night’s talk had a motion-activated floodlight outside the entrance. I think the detector was aimed more at people arriving than leaving because it took a couple of steps in the dark before it snapped on as I came out to start loading up my car.

But, when it did come on, it revealed a swirl of mist like something from a scary movie where the script calls for the atmosphere to be eerie. It was a clear sign, confirmed on the drive home by going from clear visibility to an impenetrable wall of white in a matter of a few yards, that the season is changing rapidly. This time last year, after all, we were only a month away from very heavy snowfalls.

The talk itself went very well and I had the usual pleasure of hearing, from a number of audience members, their own experiences of poisonous plants. ‘Lethal Lovelies’ is an overview of the world of poisonous plants. I joke that talking about all of them would take about four hours but that’s not entirely untruthful. To keep to the expected time, I try and pick out plants that make general points about how poisoning occurs, or more usually doesn’t occur because the taste is too awful for people to ingest a harmful amount, and plants that have the most interesting stories.

Heracleum mantegazzianum, giant hogweed

Heracleum mantegazzianum, giant hogweed

The current version of the talk sees twenty-four plants get mentioned though several of them get only a sentence or two. One of the plants is Heracleum mantegazzianum, giant hogweed, because it’s the best example of the reason why ‘Don’t touch!’ can be good advice with some plants. After the talk, a woman told me her experience of giant hogweed, some years ago, and I thought I’d write about it here because it provides an example of how people can pick up snippets of information and put them together to reach a completely erroneous conclusion.

The story was that the woman had been involved with a play group that had land backing onto a railway line. The track verge was heavily populated with Heracleum mantegazzianum and the children could reach some of the plants through the fence. This they did in order to use the hollow stems to make pea-shooters for their bellicose games in the field.

This is one of the classic routes for harm to be caused by this plant and, sure enough, the children soon developed burns around their lips where the furocoumarins from the cut stalks had been transferred to the skin.

The playgroup contacted British Rail, I said it was some years ago, to see about getting the plants removed. This was done but one of the British Rail staff involved with its removal told my audience member that giant hogweed was an invasive plant that had escaped from Kew Gardens and spread around the rail network.

Heracleum mantegazzianum, giant hogweed

Heracleum mantegazzianum, giant hogweed

That is not true but it is quite easy to see how that story came into being. Heracleum mantegazzianum is an invasive plant but it was brought to the UK by the Victorians and was, for a time, a very fashionable plant to have in your garden. This may just have been because its flower heads are very attractive but it may also have been that, being a very large plant, having it indicated that one possessed a large garden and that, in itself, would be an analogue for having a large income. It was from these Victorian gardens that giant hogweed made its way into the wild and, especially, onto riverbanks.

Senecio squalidus is Oxford ragwort. It is not a UK native but was brought to this country, from Sicily, in the first decade of the eighteenth century. Though it is thought that it was originally planted in the gardens at Badminton it was soon transferred to the Oxford Botanical Garden. By the end of the eighteenth century it was to be found growing on walls and wasteland around Oxford and, since then, has spread to most of the British Isles. This spread seems to have occurred as a result of the plant following railway lines and growing on railway embankments.

It seems, therefore, that the British Rail official’s explanation for the Heracleum mantegazzianum that caused the children’s burns was part the story of giant hogweed and part the story of Senecio squalidus but with Kew Gardens replacing the Oxford Botanical Garden.