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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 25th October 2011

Someone in a gardening forum asked the question ‘Are the berries on cotoneasters good to eat?’ The first response was full of uppercase letters and exclamation marks saying that they are poisonous and to be avoided at all costs.

I’m not going to give a verbatim report of the ensuing discussion but I thought I would blog, again, on the subject of relative risk, common sense and the Jerry Maguire Test.

I’ll start with the facts and the references I used to establish those facts.

Dr Liz Dauncey, in her Kew Garden published book 'Poisonous Plants - A guide for parent and childcare providers', uses Cotoneaster as an example of berries with low or no toxicity.

The International Poisonous Plants Checklist, by D. Jesse Wagstaff, cites references to scientific papers about poisoning and has nothing on Cotoneaster.

Cotoneaster lacteus

Cotoneaster lacteus

'Mind-Altering and Poisonous Plants of the World' with the sub-title 'A Scientifically Accurate Guide to 1200 Toxic and Intoxicating Plants', by Michael Wink & Ben-Erik Van Wyk, puts it in Poison Class III, slightly hazardous, but does not deal with it in the 1,200 plant A to Z section of the book.

'Poisonous Plants in Britain and their effects on Animals and Man', the MAFF publication, says 'It is often assumed that the berries of [Pyracantha] and other similar shrubs such as Cotoneaster are poisonous, and children who have eaten them are often referred to hospital. These berries are, however, of only doubtful or low toxicity'.
Crown copyright 1984 (Crown copyright material is reproduced with the permission of the Controller of HMSO and the Queen’s Printer for Scotland).

So, those are the facts about Cotoneaster but facts aren’t always what drives public perception about poisonous plants. I gave a fuller quote from that last source because the point about children being referred to hospital is an important one. On the Laburnum page in the A to Z section, I write ‘in a 1979 contribution to ‘The Lancet’ entitled ‘Have you Eaten Laburnum?’, R M Forrester says that there are around 3,000 hospital admissions due to Laburnum poisoning each year’. Yet, there are no reported incidents of serious harm being done to any of those children.

My belief is that press coverage, probably, created a heightened expectation of the danger posed by Laburnum and resulted in those very high figures. Of course, in the 1970s there was no such thing as the Internet but these days the source of misinformation about poisonous plants is most often to be found online.

Cotoneaster lacteus

Cotoneaster lacteus

Strictly speaking, Cotoneaster is a poisonous plant because it does contain toxins and that is why you find it listed on sites intended to warn about the possible dangers in the garden. It is even found on some American Poison Control Centre websites but they, more than other unofficial sites, are likely to over apply the precautionary principle.

There’s little point, to me, in providing a list of every plant that contains toxins not least because such a list would include a great many vegetables that schools are increasingly encouraging children to grow as a means of learning about the natural environment, nutrition and sustainability.

If you’re going to warn people against plants like Cotoneaster then you really should also warn them against just about every item in the kitchen and the bathroom.

If you apply the Jerry Maguire Test you find that there are no piles of bodies fatally poisoned by Cotoneaster. And there is a very simple reason for this; as so often, the berries aren’t pleasant to eat. With the Cotoneaster, it is not so much that the taste is unpleasant, though it is, it is that the berries aren’t at all juicy and the texture is powdery.

Even birds aren’t that anxious to eat the berries. I’ve got several hundred berry clusters on my Cotoneaster lacteus but I only found the one, pictured, showing evidence of having been eaten by the birds. Last winter, when the weather was very severe, the birds did, eventually, eat the berries but, generally, they prefer something juicier.


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