THE POISON GARDEN website      Arum maculatum berries on a Cannabis leaf 


This free script provided by JavaScript Kit

Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 5th June 2012

An email from Dr *****, in Germany, tells me that he wrote his PhD about thujone and asks if I was aware that Thuja occidentalis, white cedar, also produces thujone. The essential oil is reported to contain up to 80% thujone so you have to wonder why, when oil of wormwood from Artemisia absinthium is said to contain 40-60% thujone there is much less information about the former.

I did a quick search of a database of research papers and found that the keywords ‘Thuja’ and ‘toxicity’ produced six results but ‘Artemisia’ and ‘toxicity’ gave 99 documents.

Though my correspondent didn’t mention it, Thuja plicata, western red cedar, also has an oil containing thujone, reportedly up to 87% in fact. The International Poisonous Plants Checklist has many more citations for this species than for the occidentalis. Most refer to contact dermatitis or asthma related problems whereas the papers cited under plants in the Artemisia genus are mostly concerned with poisoning, of humans and livestock, by ingestion.

In the 19th and early 20th century, Thuja was widely used for its alleged therapeutic properties though care should be taken when reading about these because it was a favourite of Hahnemann, the exploiter of homeopathy, and, therefore, it is claimed to be efficacious in a huge range of conditions. Even so, its potential to cause harm was well-known and well-documented.1

My correspondent also developed a point that flows from what I wrote about the way plant constituents were named after the plant. He noted that this can lead to the same chemical being given different names because it occurs in different plants. He explained that 
tanacetone, found in Tanacetum vulgare, tansy, is essentially thujone. He also noted that tansy produces over ten so-called chemotypes, slight differences in the chemical composition of apparently identical plants.

From the very beginnings of my work with poisonous plants I have favoured using the botanical names because common names can get applied to completely different genera producing completely different substances. For example, ‘Jack in the pulpit’ may mean Arum maculatum or Arisaema triphyllum. Identifying a plant for medicinal use by its common name is, therefore, not to be recommended though a great many herbal preparation websites do use common names predominantly.

You might think that identifying plants by their appearance would be a better way. For some time, I’ve visited a gardening forum with a section for questions. Many of these questions are of the ‘What is this?’ variety. The site is a community of amateur gardeners but between them there are many hundreds of years of gardening experience. Nonetheless, a frequent answer to the question ‘What is this?’ is ‘Don’t know’.

Misidentification by sight is not a new problem I mentioned before that Thomas Johnson, the botanist who substantially revised John Gerard’s ‘Herbal’ for the 1633 second edition was concerned about apothecaries buying their plants from women who were not sufficiently skilled to always collect the correct plant.

Now, with today’s email, it seems you can’t always rely on correct identification of a plant being a way to be sure of what it contains. Actually, that’s not a completely new thought because I’ve noted before that Conium maculatum, poison hemlock, is said to vary in strength becoming stronger in warmer climates. In that same blog, I said;

‘use of a plant itself for medicinal purposes is a very stupid thing to do.’

The email Dr ***** was kind enough to write reinforces that opinion.


1.A Treatise on Thuja Occidentalis.  Professor H. W. Felter 1904


Full Entries


Tuesday 25th October 2016
Saturday 20th August 2016
Sunday 6th March 2016
Wednesday 3rd February 2016


Saturday 28th November 2015
Friday 27th November 2015
Monday 17th August 2015
Wednesday 15th July 2015
Friday 26th June 2015
Thursday 25th June 2015
Thursday 30th April 2015
Wednesday 29th April 2015
Wednesday 11th March 2015
Tuesday 3rd March 2015
Saturday 28th February 2015
Sunday 22nd February 2015

November 2014

Monday 24th November 2014
Saturday 8th November 2014

October 2014

September 2014

Wednesday 24th September 2014
Monday 1st September 2014

August 2014

Tuesday 26th August 2014
Saturday 16th August 2014
Tuesday 5th August 2014
Friday 1st August 2014

July 2014

Sunday 27th July 2014
Wednesday 23rd July 2014
Sunday 13th July 2014
Sunday 6th July 2014
Tuesday 1st July 2014

June 2014

Wednesday 25th June 2014
Tuesday 24th June 2014
Sunday 22nd June 2014
Monday 9th June 2014
Wednesday 4th June 2014

May 2014

Monday 26th May 2014
Sunday 18th May 2014
Wednesday 14th May 2014

April 2014

Sunday 13th April 2014
Saturday 5th April 2014
Thursday 3rd April 2014
Tuesday 1st April 2014

March 2014

Monday 31st March 2014
Tuesday 25th March 2014
Friday 21st March 2014
Monday 17th March 2014
Sunday 16th March 2014
Tuesday 11th March 2014
Tuesday 11th March 2014
Thursday 6th March 2014
Wednesday 5th March 2014
Saturday 1st March 2014

February 2014

Thursday 27th February 2014
Monday 24th February 2014
Wednesday 19th February 2014
Monday 17th February 2014
Thursday 13th February 2014
Monday 4th February 2014
Monday 3rd February 2014
Saturday 1st February 2014

January 2014

Thursday 28th January 2014
Thursday 23rd January 2014
Friday 17th January 2014
Wednesday 15th January 2014
Monday 13th January 2014
Thursday 9th January 2014
Tuesday 7th January 2014
Wednesday 1st January 2014

December 2013

Monday 23rd December 2013
Friday 20th December 2013
Tuesday 17th December 2013
Friday 14th December 2013
Thursday 12th December 2013
Sunday 8th December 2013
Wednesday 4th December 2013
Sunday 1st December 2013

November 2013

Friday 29th November 2013
Wednesday 27th November 2013
Tuesday 26th November 2013
Friday 22nd November 2013
Monday 18th November 2013
Friday 15th November 2013
Thursday 14th November 2013
Sunday 10th November 2013
Thursday 7th November 2013
Wednesday 6th November 2013
Friday 1st November 2013

October 2013

Thursday 31st October 2013
Sunday 27th October 2013
Wednesday 23rd October 2013
Monday 21st October 2013
Friday 18th October 2013
Friday 11th October 2013
Wednesday 9th October 2013
Tuesday 8th October 2013
Monday 7th October 2013
Tuesday 1st October 2013

September 2013

Monday 30th September 2013
Saturday 28th September 2013
Friday 27th September 2013
Monday 23rd September 2013
Sunday 15th September 2013
Monday 9th September 2013
Tuesday 3rd September 2013
Sunday 1st September 2013

August 2013

Sunday 8th September 2013
Tuesday 3rd September 2013
Sunday 1st September 2013

Tuesday 27th August 2013
Sunday 25th August 2013
Monday 19th August 2013
Friday 16th August 2013
Tuesday 13th August 2013
Friday 9th August 2013
Friday 2nd August 2013
Thursday 1st August 2013

July 2013

Saturday 27th July 2013
Sunday 21st July 2013
Wednesday 17th July 2013
Monday 15th July 2013
Saturday 13th July 2013
Friday 12th July 2013
Thursday 11th July 2013
Wednesday 10th July 2013
Tuesday 9th July 2013
Saturday 6th July 2013

June 2013

Friday 28th June 2013
Tuesday 25th June 2013
Friday 21st June 2013
Thursday 20th June 2013
Wednesday 19th June 2013
Saturday 15th June 2013
Sunday 9th June 2013
Saturday 8th June 2013
Saturday 1st June 2013

May 2013

April 2013

March 2013

February 2013

January 2013

December 2012

November 2012

October 2012

September 2012

August 2012

July 2012 blog

June 2012 blog

May 2012 blog

April 2012 blog

March 2012 blog

February 2012 blog

January 2012 blog

December 2011 blog

November 2011 blog

October 2011 blog

September 2011 blog

August 2011 blog

July 2011 blog

June 2011 blog


The POISON GARDEN website is not connected with Alnwick Garden Enterprises Ltd and/or The Alnwick Garden Trust.