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.

Saturday 16th August 2014

One of the ‘facts’ about Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort, that gets spouted in almost any discussion about the plant is that it is increasing out of control. I know enough about the Internet to know that even a complete refutation of that claim would not prevent it being made but I did hope a new report into the frequency and abundance of the five weeds covered by the Weeds Act 1959 as well as Invasive Non-native Species (INNS) would provide a definitive answer to the point, one way or the other.

So, I was disappointed to find that a report from the Centre for Ecology & Hydrology entitled ‘Analysis of change in frequency and abundance of injurious weed and selected invasive non native species in England: Final report for Defra. Project WC1042.’ did not offer any level of certainty about the issue.

The report is an attempt to evaluate the prevalence of the five weeds covered by the Weeds Act 1959 and to look at the situation regarding invasive non-native species (INNS) such as Heracleum mantegazzianum, giant hogweed, Impatiens glandulifera, Himalayan balsam, and Fallopia japonica, Japanese knotweed. The main source of information is the Countryside Survey of Great Britain though the report says that the survey areas do not offer sufficient occurrences of the INNS to make a meaningful assessment.
So there’s the first problem. Survey areas that do not have enough of the INNS to allow an assessment are, clearly, not representative of the country as a whole. That has to be kept in mind when reading what it says about common ragwort, in particular.

There’s a further problem; what the report calls recorder effort. The authors have had to try and find ways to allow for the different amount of detail provided from area to area and the difference from one survey to the next in the same area. It is, of course, impossible to know how accurate the adjustments made for this are but, I suspect, they are not that accurate.

As well as using the countryside survey the authors have drawn on other work. This includes a detailed analysis of 40cm x 40cm ‘cells’ within 10m x 10m plots on 11 areas conducted by the Environmental Change Network (ECN). On page 19 of the report, Figure 3.2 shows the proportions of cells counted that were occupied by common ragwort at these ECN sites.

For the six sites shown on the graph, Porton Down is so different from all the others that it cannot be said that the figure as a whole offers a meaningful snapshot of the national situation.

With these limitations in mind, I think everyone should be careful about how these results are used. I’m not inclined to rely on the findings, summarised  in Figure 5.1(b) on page 42 of the report, that suggest that common ragwort increased in frequency from 1990 to 1998 before falling back so that, by 2007, it was less frequent than it had been in 1990. The furthest I would want to go is to say the survey finds there is no justification for claims that common ragwort is spreading out of control or that it increases year on year.
The report’s authors are well aware of the limits of the data available to them and are, therefore, wary of drawing too many conclusions. Against that background, it is important that they say that the frequency of common ragwort in the survey plots was positively related to the use of land by horses.

’m very comfortable with saying that there is some component of the common ragwort distribution story that results from over-grazing by horses. Of course, common ragwort occurs in places where there are no horses but, equally, those places are not a problem for horse-owners unless the land is being used to produce forage.

What the report is saying is that, if there is enough space in a paddock then the horse(s) in that paddock will not cause enough disturbance of the ground to provide opportunities for common ragwort to thrive.

A simplistic solution would seem to be to calculate what area of land each horse needs to avoid such disturbance and mandate that for all paddocks. Of course, it is not as easy as that because different ground types and different climates, even year to year in the same area, mean that what is adequate in one place at one time will be insufficient in a different place or year.

Online, there is some guidance for ‘reasonable’ conditions but I have to say I am disturbed to find that the British Horse Society (BHS) recommends around half the area recommended by others.

What needs to come from this report is the recognition that the answer to common ragwort in horse paddocks has to come from changes in the management of the horses not of the plant.

The BHS should be pressed to increase its recommended minimum pasture area and should focus its attention on better care from horse-owners. If it won’t campaign to bring about changes then legislation might be required to set, at least, the very minimum area per horse that on well-drained, good ground would prevent widespread disturbance.

Of course, any move to increase the paddock available would make keeping horses more expensive and that would lead to horses being abandoned. That’s why I think it is time for the proposal made by the Princess Royal to be taken seriously. She said, a few months ago, that there needed to be a UK market for horsemeat so that there was both a disposal route for unwanted horses and an incentive to take proper care.

Submit a Comment

You can send comments via the contact page but please be sure to say what blog entry you are commenting on.

Follow @thepoisongarden on Twitter

Full Entries


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

August 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 2013April 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.