Ragwort (Senecio jacobaea) supports an enormous number of species of insect. The Biological Records Centre's database of Insects and their Food Plants* lists an astonishing 97 species, at least 30 of which are entirely dependent on ragwort for their survival. A further 52 are 'highly reliant' on it.
Unfortunately a certain amount of hysteria about the plant has spread following some inaccurate stories in the press and on social media resulting in this useful wildflower being uprooted wholesale in public areas, far in excess of governmental advice.
Here are some facts about the dangers of Ragwort :
There is no risk of poisoning to humans by absorption through the skin (touching it).
A human would have to eat as much as 14lbs of ragwort to reach a lethal dose (extrapolating from the percentages discovered in horses and cattle). Compare this to just 2 leaves of Foxglove (Digitalis) which is a plant that seems to terrify no-one.
A horse or cow would have to eat 6-25% of its body weight in ragwort to cause a fatality. A goat would have to eat between 125% and 404% of its body weight in ragwort for the same effect.
Animals don't usually choose to eat ragwort unless they have no other choice or are starving, because it has a repellent smell and taste. Cases of ragwort poisoning occur when dried ragwort is mixed into hay, and the animals can't detect it. Dogs don't eat ragwort any more than humans do and, don't forget, they'd have to eat a lot to become sick.
The alkaloids in the ragwort are excreted within 24-48hrs so you would have to eat ragwort regularly to build up enough liver damage to be fatal.
About 3% of all plants contain the same pyrrolizidine alkaloids that occur in ragwort
We commonly grow many plants in our gardens that are extremely toxic to humans and animals, such as Daffodils, Brugmansia, Monkshood, Delphiniums, Yew, Foxgloves, Delphiniums. Even the Ricin plant (Ricinus communis) is often used in bedding displays in parks and gardens.
* To use the BRC's database, use the headings at the top of the page. For example, to find out how many different species of insect a daisy supports, click on "Search for host plants" and type Bellis perennis or just Bellis into the search box. You will have to look up the Latin name of the plant.
I have cribbed the information on this page from a variety of other websites which have references to scientific studies. If you would like to find out more detail, I would recommend you visit one of the following:
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