Jacobaea vulgaris


Jacobaea vulgaris, synonym Senecio jacobaea, 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.
Common names include ragwort, common ragwort, stinking willie, tansy ragwort, benweed, St. James-wort, stinking nanny/ninny/willy, staggerwort, dog standard, cankerwort, stammerwort. In the western United States it is generally known as tansy ragwort, or tansy, though its resemblance to the true tansy is superficial.
In some countries it is an invasive species and regarded as a noxious weed. 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.

Description

The plant is generally considered to be biennial but it has the tendency to exhibit perennial properties under certain cultural conditions. The stems are erect, straight, have no or few hairs, and reach a height of. The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word "stinking" arise because of the unpleasant smell of the leaves. The hermaphrodite flower heads are diameter, and are borne in dense, flat-topped clusters; the florets are bright yellow. It has a long flowering period lasting from June to November.
Pollination is by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20- to 60-headed, flat-topped corymbs. The achenes have dandelion-like groups of prickly hairs called pappuses, which help seed dispersal by the wind. The number of seeds produced may be as large as 75,000 to 120,000, although in its native range in Eurasia very few of these would grow into new plants and research has shown that most seeds do not travel a great distance from the parent plant.

Taxonomy

Two subspecies are accepted:
  • Jacobaea vulgaris ssp. vulgaris – the typical plant, with ray florets present.
  • Jacobaea vulgaris ssp. dunensis – the ray florets are missing.

    Distribution

Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Great Britain and Ireland, where it is native, it is listed as a noxious weed.
Ragwort is abundant in waste land, waysides and grazing pastures. Its natural habitat is sand dunes, but it is commonly found along road sides, railways and in light, low fertility soil.
It has been introduced in many other regions, and is listed as a weed in many. These include:
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. It was rated in the top 10 for most nectar production in a UK plants survey conducted by the AgriLand project which is supported by the UK Insect Pollinators Initiative. It also was the top producer of nectar sugar in another study in Britain, with a production per floral unit of.
In the United Kingdom, where the plant is native, ragwort provides a home and food source to at least 77 insect species. Thirty of these species of invertebrate use ragwort exclusively as their food source and there are another 22 species where ragwort forms a significant part of their diet.
English Nature identifies a further 117 species that use ragwort as a nectar source whilst travelling between feeding and breeding sites, or between metapopulations. These consist mainly of solitary bees, hoverflies, moths, and butterflies such as the small copper butterfly. Pollen is collected by solitary bees.
Besides the fact that ragwort is very attractive to such a vast array of insects, some of these are very rare indeed. Of the 30 species that specifically feed on ragwort alone, seven are officially deemed nationally scarce. A further three species are on the IUCN Red List. In short, ragwort is an exclusive food source for ten rare or threatened insect species, including the cinnabar moth, the picture winged fly, the scarce clouded knot horn moth, and the Sussex emerald moth. The Sussex Emerald has been labelled a Priority Species in the United Kingdom Biodiversity Action Plan. A priority species is one which is "scarce, threatened and declining". The remainder of the ten threatened species include three species of leaf beetle, another picture-winged fly, and three micro moths. All of these species are Nationally Scarce B, with one leaf beetle categorised as Nationally Scarce A.
The most common of those species that are totally reliant on ragwort for their survival is the cinnabar moth. The cinnabar is a United Kingdom Biodiversity Action Plan Species, its status described as "common and widespread, but rapidly declining".

Poisonous effects

Ragwort contains many different alkaloids, making it poisonous to many animals. . 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. There is a strong variation between plants from the same location in distribution between the possible alkaloids and even the absolute amount of alkaloids varies drastically.
Ragwort is of particular concern to people who keep horses and cattle. In areas of the world where ragwort is a native plant, such as Britain and continental Europe, documented cases of proven poisoning are rare. Horses and cattle normally recognize and do not eat fresh ragwort due to its taste. However, they may still consume it if there is not enough other food. Further, if ragwort is included in hay or silage, livestock will not be able to recognize it, and it will moreover contaminate the entire batch. 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. Signs that a horse has been poisoned include yellow mucous membranes, depression, and lack of coordination.
There is no definitive test for the poisoning however, since megalocytosis is not a change in the liver which is specific to ragwort poisoning. It is also seen in poisoning by other alkylating agents, such as nitrosamines and aflatoxins. Aflatoxins are a common contaminant formed in feedstuffs by moulds. 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.
The alkaloid does not actually accumulate in the liver but a breakdown product can damage DNA and progressively kills cells. About 3--7% of the body weight is sometimes claimed as deadly for horses, but an example in the scientific literature exists of a horse surviving being fed over 20% of its body weight. 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.
The alkaloids can be absorbed in small quantities through the skin but studies have shown that the absorption is very much less than by ingestion. Also they are in the N-oxide form which only becomes toxic after conversion inside the digestive tract and they will be excreted harmlessly.
Some sensitive individuals can suffer from an allergic reaction because ragwort, like many members of the family Compositae, contains sesquiterpene lactones which can cause compositae dermatitis. These are different from the pyrrolizidine alkaloids which are responsible for the toxic effects.
Honey collected from ragwort has been found to contain small quantities of jacoline, jacobine, jacozine, senecionine, and seneciphylline, but the quantities have been judged as too minute to be of concern.

Control

As indicated above, common ragwort has become a problem in several areas in which it has been introduced, and various methods are employed to help prevent its spread.
In many Australian states ragwort has been declared a noxious weed, and landholders are required to remove it from their property by law. In the island state of Tasmania, ragwort is responsible for more than half of the total costs of that state's control of invasive species. The species has been calculated as the 8th most expensive invasive species in terms of cost to Australian farmers, at over over 60 years.
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.

Legislation

Ireland

In Ireland, the Noxious Weeds Order 1937, issued under the Noxious Weeds Act 1936, declares ragwort as a noxious weed, requiring landowners to control its growth.
File:Common Ragwort Glen Coe.jpg|thumb|Blooming ragwort located in Glen Coe in the Highlands of Scotland

United Kingdom

In the United Kingdom, common ragwort is one of the five plants named as an injurious weed under the provisions of the Weeds Act 1959. The word injurious in this context indicates that it could be harmful to agriculture, not that it is dangerous to animals, as all the other injurious weeds listed are non-toxic. 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.
The Ragwort Control Act 2003 provides for a code of practice, which the government states is guidance, on ragwort and does not place any further legal responsibilities on landowners to control the plant.