Tansy ragwort - Senecio jacobaea
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Ragwort (Senecio jacobaea) is a very common wild flower in the family Asteraceae that is found throughout Europe, usually in dry, open places, and has also been widely distributed as a weed elsewhere.
Ragwort can be found along road sides and waste grounds, and grows in all cool and high rainfall areas.
The Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Britain 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.
Ragwort contains many different alkaloids, making it poisonous to animals. In theory it is also toxic to humans but the dose required would be enormous. Alkaloids which have been found in the plant are acetylerucifoline, (Z)-erucifoline, (E)-erucifoline, 21-hydroxyintegerrimine, integerrimine, jacoline, jaconine, jacobine, jacozine, riddelline, retrorsine, senecivernine, senecionine, seneciphylline, spartioidine, and usaramine.
Ragwort is of concern to people who keep horses, as well as 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. In other areas the plant may become much more invasive and constitute a problem. Although horses do not normally eat ragwort due to its bitter taste, if the growth is particularly dense or if it has been picked and dried out, and it is taken while grazing, the result, if a large 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 and without apparent harm. They seem to profit slightly from eating it, according to some reports [attribution needed] the alkaloids kill worms in the sheep's stomach.
The danger of Ragwort is that the toxin can have a cumulative effect. The toxin does not actually accumulate in the liver but a breakdown product can damage DNA and gradually kill 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. However, because of the mode of poisoning is through affecting DNA molecules, very small amounts are unlikely to cause harm as they will be below the threshold to cause damage. The toxic breakdown products can also be metabolised by the liver before damage occurs. The effect of low doses is also lessened by the destruction of the original alkaloids by the action of bacteria in the digestive track before they reach the bloodstream. There is no known antidote or cure to poisoning, but at least one example is known from the scientific literature of a horse making a full recovery once consumption has been stopped.
Honey collected from Ragwort has been found to contain small quantities of jacoline, jaconine, jacobine, jacozine, senecionine, and seneciphylline. However these are unlikely to cause harm since the quantities consumed are below the harm threshold.
Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers