Ragwort

Ragwort (Jacobaea vulgaris / 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, benweed, tansy ragwort, St. James-wort, ragweed, Stinking Nanny/Ninny/Willy, staggerwort, Dog Standard, cankerwort, stammerwort, mare’s fart and cushag. In the western US it is generally known as Tansy Ragwort, or “Tansy”, though its resemblance to the true tansy is superficial.

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 stems are erect, straight, have no or few hairs, and reach a height of 0.3–2.0 metres (1 ft 0 in–6 ft 7 in).

The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word “stinking” (and Mare’s Fart) arise because of the unpleasant smell of the leaves. The hermaphrodite flower heads are 1.5–2.5 centimetres (0.59–0.98 in) 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 (In the northern Hemisphere).

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. This 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.

Ragwort can be found along road sides and waste grounds, and grows in all cool and high rainfall areas.

Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Britain and Ireland it is listed as a weed. In the USA it has been introduced, and is present mainly in the North West and North East: California, Idaho, Illinois, Maine, Massachusetts, Michigan, Montana, New Jersey, New York, Oregon, Pennsylvania, and Washington.

In South America it grows in Argentina, in Africa in the north, and on the Asian continent in India and Siberia. It is widespread weed in New Zealand and Australia. In many Australian states ragwort has been declared a noxious weed.

This status requires landholders to remove it from their property, by law. The same applies to New Zealand where farmers sometimes bring in helicopters to spray their farms if the ragwort is too widespread.

Ragwort Removal Control (IWM)
Ragwort Removal Control (IWM)

Ragworts Poisonous effects

Ragwort contains many different alkaloids, making it poisonous to certain animals. (EHC 80,section 9.1.4). 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 (pp322 Appendix II).

Other alkaloids claimed to be present but from an undeclared source are acetylerucifoline, (Z)-erucifoline, (E)-erucifoline, 21-hydroxyintegerrimine, integerrimine, jacoline, riddelline, senecivernine, spartioidine, and usaramine.

Ragwort is of 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 do not normally eat fresh ragwort due to its bitter taste. It loses this taste when dried and can become a danger in hay. The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver. Signs that a horse has been poisoned include yellow mucus membranes, depression, and lack of coordination. Animals may also resort to the consumption of ragwort when there is shortage of food. In rare cases they can even become addicted to it. Sheep, in marked contrast, eat small quantities of the plant with relish. Sheep and goats suffer the same process of liver destruction but at a reduced rate to horses and pigs.

The danger of Ragwort is that the toxin can have a cumulative effect. 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.

Ragwort poses little risk to the livers of humans since, although it is theoretically poisonous to humans, it is distasteful and is not used as a food. 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 compositae family contains sesquiterpine lactones which can cause compositae dermatitis. These are different from the pyrrolizidine alkaloids which are responsible for the toxic effects.

Honey collected over 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.