The vexed question of risk came up twice today on very different issues. If you’re a regular reader of this blog you’ll know that I think there is a lot of crying wolf about poisonous plants from all directions but they are poisonous plants so, surely, some precautions are necessary.
I received an email from someone who wanted to know if it would be safe to grow vegetables where Aconitum napellus, monkshood, had once grown providing great care was taken to remove every trace of the previous inhabitants. In reply, I pointed out that poisonous plants often grow near food plants but people don’t give that any thought. I had in mind the blackberry brambles, Rubus fruticosus, that people pick from hedgerows without even wondering what other plants grow in close proximity.
I also mentioned the pea farmer who had Atropa belladonna, deadly nightshade, growing in his fields and pulled the plants out before harvesting but didn’t worry that adjacent plants might have become tainted.
But I stopped short of saying my enquirer should just go ahead and not bother with clearing the ground carefully because there is just a tiny risk that a piece of left over root could get confused with Pastinaca sativa, parsnip, assuming that is one of the vegetables being planted.
The second thing that brought this question to mind was a plant offer in the current ‘Radio Times’. It’s for ‘hardy Oleander bushes’ and, though not said, the picture shows a variety of Nerium oleander. I won’t dispute the ‘hardy’ claim since this may be a variety that has been bred for that characteristic but, in the Alnwick Garden, the oleander was only on display from the end of May to the end of October and never produced flowers.
The ‘small print’, albeit in bold type, says ‘Oleander sap can be toxic if ingested or in contact with the skin’. OK, that’s a warning, but is it good enough? Liz Dauncey, in 'Poisonous Plants: a guide for parents and childcare providers', says ‘Ingestion may result in severe poisoning’ and the Horticultural Trades Association rates it a Category ‘B’ potentially harmful plant. (Remember that the HTA has only one plant in category ‘A’ and that one never sold in UK garden centres so Category ‘B’ is, really, as bad as it gets.)
‘Poisonous Plants and Fungi’ by Cooper, Johnson and Dauncey comes out more strongly by saying, ‘It has long been recognized that this is an extremely dangerous plant’ and ‘Every part of the plant contains glycosides that affect the action of the heart’. Wink and van Wyk, in ‘Mind-altering and Poisonous Plants of the World’ say ‘All parts of the plant are extremely poisonous’ and Frohne and Pfander, in ‘A Colour Atlas of Poisonous Plants’ say that the plant contains ‘cardiac glycosides of the cardenolide type in all parts’.
The important point here, it seems to me, is that all three of those books say that the whole plant is toxic not just the sap. Drawing particular attention to the sap might make someone believe that there is nothing to fear from the rest of the plant.
I can’t say often enough that the number of incidents of accidental poisoning resulting directly from a plant is very, very small so I don’t think the advert for these plants should scream ‘POISON’ in big black letters but I do think any warning has to be complete.