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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 21st May 2013

I’ve been having an argument with myself about Heracleum mantegazzianum, giant hogweed. If you follow that link to the plant page you’ll see that I have blogged about it on many occasions and, last year, tracked the development of a number of patches of the plant in Edinburgh. In those pieces, I expressed my concern that allowing the plants to mature and set seed would result in their proliferation. With the very nasty burns that can arise from contact with the plant, I feared that many more people could be harmed if no attempt is made to control its spread.

There is another recurring theme to this blog and that is the Jerry Maguire Test. Very early in the life of this blog I explained that I am wary of accepting the voices of doom who pronounce on the dangers of one plant or another because it is, generally, difficult to find large numbers of case reports to show that the potential for harm is being realised. And there is my internal argument. Am I doing what I condemn in others; making a fuss about a plant that, in reality, doesn’t cause a lot of harm?

Last year, I blogged on two occasions  one in July and the other in September about newspaper reports of children and young people suffering unpleasant burns after contact with giant hogweed.

The fact that these stories were published means that incidents of harm do occur but it also suggests that they are not that common. No editor, for example, would consider publishing a story about someone being stung by a wasp. Such incidents are far too frequent to deserve publication no matter how silly the ‘silly season’ was for his newspaper.

I’ve done another couple of searches to see if I could find other incidents to add to the three covered by those two previous blogs and I did find just one more, in central Fife last July. What I have not found is any incidents reported in Edinburgh. It could be that I have been over-stating the risk and, reading back I see I did consider that possibility when I wrote;

‘I can't help thinking that one of two things will happen in the next couple of months. Either there will be lots of reports of people suffering burns from contact with these plants or there will be further evidence that, although we live our lives surrounded by potentially harmful plants, we mostly avoid the harm they could cause.’

But, if the actual harm caused by Heracleum mantegazzianum is in doubt, its spread is much more certain. I returned to the same places where I took most of my photographs last year to find that the giant hogweed is, again, thriving and there is evidence of its spread.

Take this picture from last July:

Heracleum mantegazzianum, giant hogweed 

And compare it with this one taken last week:

Heracleum mantegazzianum, giant hogweed 

I did comment last year that most of the hogweed I saw was at the side of a road where there was no footpath so the chance of contact was greatly reduced. And those populations are, again, thriving. This picture shows last year's dead flower stalks in amongst this year’s growth.

Heracleum mantegazzianum, giant hogweed 

As feared, though, the plant is spreading, albeit slowly, so far. These two images were taken on the footpath side of the road and anyone walking along this road could easily have contact with them.

Heracleum mantegazzianum, giant hogweed 


Heracleum mantegazzianum, giant hogweed 

I always say in my talks that the difference between a poisonous plant and a harmful plant is whether people are exposed to the poisons. Contacting giant hogweed on the edge of a footpath is, clearly, more likely than when the plants are on the other side of the road. Even so, past form suggests that there will be very few serious incidents. I hope that is the case.

So, I’m concerned because giant hogweed burns are particularly unpleasant but I’m trying to avoid over-stating the potential for actual harm.

As I was walking along the footpath I spotted this;

Heracleum mantegazzianum, giant hogweed 

It is rather early for Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort, to be in flower so I think this is likely to be Senecio squalidus, Oxford ragwort, though I’m not great at identifying the different species. Of the two plants in that image I think I know which one will get the greater, and more hysterical, coverage through the summer.


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