I have to admit to a little editing of this question. When it came to Alice and me (as question askers for the evening) the question read "Which common weed is poisonous to horses and cattle but not sheep?" and the answer was "Ragwort (accept Kadle Dock)". I decided to move the reference to kadle dock into the question, partly to make it more specific and partly to remove any possible confusion over which answer was expected.
The Plough Horntails had no problem in giving the correct answer, but I'd never heard of kadle dock and I knew nothing about ragwort, so in the days after the MQL Plate Final, with the questions already on the website, I decided to do a bit of delving. And my findings made me wonder where this question had actually come from.
Confusingly, ragwort seems to have two scientific names: Jacobaea vulgaris and Senecio jacobaea. If you type "ragwort", or the second of those two Latin names, into Wikipedia, you are redirected to the page for Jacobaea vulgaris. Wikipedia gives no fewer than twelve alternative names for this "very common wild flower", not including ragwort; but none of them is kadle dock.
If you type "kadle dock" into the Bing search engine (the one that Firefox, my web browser of choice, takes me to by default), the top result is from a website called "the Invasive Species Compendium" – CABI for short (search me ...). The entry is for Senecio jacobaea, and the common name given for this species is "common ragwort".
CABI gives over sixty alternative names for Senecio jacobaea, including kadle dock (and cradle dock). It lists the plant as an invasive species because it "has spread rapidly in Canada, the north–western and Pacific States of the USA, New Zealand and Tasmania and the southern states of Australia following its accidental introduction from Europe over the last 150 years." It goes on to mention its toxic effects on livestock. (Wikipedia agrees that "Ragwort is of concern to people who keep horses and cattle".)
Health Benefits Times (third on Bing's list) describes ragwort as "the horse killer", and has a very informative video (which is actually just a voice–over to a series of images).
The second entry on Bing's list is a page from www.spookspring.com – a site run by one James Burton, of whom I know nothing further. This has a section on the celery/carrot/parsley family of plants (Umbelliferae), and it lists kadle dock as a Cheshire dialect name for cow parsley (Anthriscus sylvestris) – a completely different species.
Someone seems to have got confused here. The Plough Horntails seem to agree with the setter of this MQL question that kadle dock is ragwort, so I suspect it's James Burton.
The most interesting aspect of all this, however – for me at least – is that the fourth entry in Bing's list for "kadle dock" is from ... Macclesfield Quiz League, Questions from 25 September 2018!
Google, on the other hand, doesn't seem to be aware of the MQL entry. From now on, I'm definitely going to go along with Firefox's default, and Bing is going to be my search engine of choice!
© Macclesfield Quiz League 2018