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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Sunday 14th August 2011

Something is eating my deadly nightshade. It’s three weeks since I posted a photo-blog of the berries developing on my Atropa belladonna and said I would post again with the ripe berries. I’m still waiting for the berries to ripen, and the absence of sunshine for most of the last three weeks suggests I may still have to wait a while.

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade

But, now, the question is whether whatever is eating the plant will complete its work before the berries get the chance to ripen.

It’s a very practical example of the fact, which is sometimes ignored, that a substance is not always a poison to every creature.  I’ve written before 30th June about the situation regarding bees and toxins getting into honey but it is not just bees that can tolerate things humans would find toxic.

The two particular instances I refer to about the difference between species are Nepeta faassenii, catmint, and Conium maculatum, poison hemlock.

It is well-known that cats are attracted to catmint, or catnip as it is sometimes called. There is little doubt that the plant is psychoactive for felines but, I think, calling it ‘cannabis for cats’, whilst alliteratively pleasing, is wrong. Its effect on cats seems to be exciting, at least initially, rather than the sort of calming ‘chilling out’ effect usually ascribed to cannabis. Mind you, the excitation does seem to be of limited duration and is followed by a more narcotic effect.

It was the effect of Nepeta faassenii on the feral cat who lived in the Alnwick Garden that gave me the title ‘Is That Cat Dead?’ for my book. Digger, a female cat who appeared on the site early in the construction phase, would come into the Poison Garden, almost every afternoon, thrash around in the catmint and then, when the excitation subsided, sleep it off under the Artemisia absinthium. The sleep was so deep that numerous visitors would ask about her condition and I’m not convinced there were not some who really thought we would leave a dead animal on display.

I have had, thankfully just a few, people ask if the cat pictured on the cover of the book is dead. One reason I went with that design was that it only takes a brief application of common sense to realise that no-one would think that was a good way to encourage sales. And applying common sense is so often the best way of approaching the more extravagant claims about poisonous plants and their effects.

Nepeta faaseenii, catmint

Nepeta faaseenii, catmint

So, if every creature responded to plants in the same way, you would expect catmint to be an intoxicant for human beings. Instead it has the reputation, I stress that it is just a reputation not a scientifically established fact, of causing anger and hatred if ingested by man. That leads to the story that the hangman would consume catmint on a working day in order to put him in the right frame of mind to kill complete strangers.

The other plant where the difference in effects is significant is Conium maculatum, poison hemlock. The principal alkaloid is called coniine and is a peripheral nervous system poison to humans. That is, it causes a numbing paralysis in the extremities that spreads up the body before causing paralysis of the chest producing death from asphyxiation.

For birds, however, coniine has no effect and is not metabolised at all. This means it is stored in the tissue unchanged. This has led to documented cases of illness and, even, death in those, especially in southern Europe, who catch and eat migrating birds as they move south in the autumn.

So, I’m sure that whatever is eating my deadly nightshade is suffering no consequences though I might wish it were otherwise.