Senecio jacobaea,[2] is a very common wild flower in the family Asteraceae that is native to northern Eurasia, usually in dry, open places, and has also been widely distributed as a weed elsewhere.

In the UK, where it is native, it is often unwanted because of its toxic effect for cattle and horses, but it is also valued for its nectar production which feeds insect pollinators and its ecological importance is thus considered significant.

The plant is generally considered to be biennial but it has the tendency to exhibit perennial properties under certain cultural conditions (such as when subjected to repeated grazing or mowing).

The hermaphrodite flower heads are 1.5–2.5 centimetres (0.6–1.0 in) diameter, and are borne in dense, flat-topped clusters; the florets are bright yellow.

[14] Its natural habitat is sand dunes, but it is commonly found along road sides, railways and in light, low fertility soil.

These include:[citation needed] Although the plant is often unwanted by landowners because of its toxic effect for cattle and horses, and because it is considered a weed by many, it provides a great deal of nectar for pollinators.

English Nature identifies a further 117 species that use ragwort as a nectar source whilst travelling between feeding and breeding sites, or between metapopulations.

The cinnabar is a United Kingdom Biodiversity Action Plan Species, its status described as "common and widespread, but rapidly declining".

Alkaloids which have been found in the plant confirmed by the WHO report EHC 80 are -- jacobine, jaconine, jacozine, otosenine, retrorsine, seneciphylline, senecionine, and senkirkine (p. 322 Appendix II).

[23][24] In areas of the world where ragwort is a native plant, such as Britain and continental Europe, documented cases of proven poisoning are rare.

[citation needed][26] The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver of a form identified as megalocytosis where cells are abnormally enlarged.

Research in the United Kingdom has produced results showing megalocytosis, which may be due to various causes, to be a relatively uncommon cause of liver disease in horses.

[citation needed] The effect of low doses is lessened by the destruction of the original alkaloids by the action of bacteria in the digestive tract before they reach the bloodstream.

There is no known antidote or cure to poisoning, but examples are known from the scientific literature of horses making a full recovery once consumption has been stopped.

[34] It is also legislated as a noxious weed in New Zealand, where farmers sometimes bring in helicopters to spray their farms if the ragwort is too widespread.

Under the terms of this Act, a land occupier can be required by the Secretary of State for Environment, Food and Rural Affairs to prevent the spread of the plant.

However, the growth of the plant is not made illegal by the Act and there is no statutory obligation for control placed upon landowners in general.

They absorb alkaloids from the plant and become distasteful to predators, a fact advertised by the black and yellow warning colours.

Culpeper was an astrological botanist and thought the plant was "under the command of Dame Venus, and [it] cleanses, digests, and discusses.