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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Sunday 11th September 2011

Someone on the Pregnancy Forum UK was concerned about a plant with black berries that their child was paying interest in. Judging from the responses, the initial posting didn’t include a photo but one had been added the suggestions started. The overall view was that it was one of the St John’s Worts; a number of species in the genus Hypericum have that common name.

Hypericum perforatum is the plant most commonly called St John’s Wort but Hypericum androsaemum is also described that way as well as being known as tutsan. Just as it seemed that there was going to be agreement that the plant in the picture was Hypericum androsaemum, tutsan, someone posted in a very definite style to say that it was Atropa belladonna, deadly nightshade.

It appears that a Google image search led them to my 19th August blog that has one small picture of deadly nightshade berries. As there may be other people interested in differentiating between these two plants, I thought I’d blog about it rather than sign up to another forum just to make one post.

The differences between the two are quite easy to spot as, I hope, these three pairs of pictures show. I’m only interested in the berries; the flowers are veryt different and no-one would mistake a flowering Hypericum androsaemum for Atropa belladonna.


First the earliest signs of berries forming. The deadly nightshade produces a small, round green berry whereas the St John’s wort, tutsan, starts out yellow.

     Atropa belladonna, deadly nightshade     Hypericum androsaemum, St John's wort


During the development stage, the Atropa belladonna remains green and simply enlarges. The Hypericum androsaemum turns from yellow to a pale red.


     Atropa belladonna, deadly nightshade     Hypericum androsaemum, St John's wort


Once fully mature, the deadly nightshade is shiny black and spherical, looking quite like a cherry, whereas the St John’s wort is not quite as black, less shiny and, crucially, for differentiating the two, the shape is a prolate ellipsoid meaning it looks like a grape.


     Atropa belladonna, deadly nightshade     Hypericum androsaemum, St John's wort


I hope these images are sufficient for you to reliably separate Atropa belladonna from Hypericum androsaemum. You can see more images of deadly nightshade on the plant page or in the photo gallery and the 2011 gallery has some larger images of Hypericum androsaemum.