|Type:||Biennial or perennial|
|Weediness:||Weedy, invasive in some regions|
|Height and spread:||0.3-2.0 meters tall|
|Toxicity and edibility:||Highly toxic to livestock|
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.
(For the North American species, see Packera obovata.)
Alternative names include Cushag, Tansy Ragwort, St. James-wort, Ragweed, Stinking Nanny/Ninny/Willy, Staggerwort, Dog Standard, Cankerwort, Stammerwort and Mare's Fart. In the western US it is generally known as "Tansy Ragwort", or even more confusingly "Tansy", though its resemblance to the true tansy is superficial at best. This is a potentially dangerous misuse of names, since the true tansy has been used for culinary purposes.
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, cattle, goats, and sheep. 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 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. In the United Kingdom, Common Ragwort (Senecio jacobaea) 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 (DEFRA) 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 plant is biennial or perennial. The stems are erect, straight, have no or few hairs, and reach a height of 0.3-2.0 meters. 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 cm 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.
Sunny locations, adaptable to a wide range of soils.
Two subspecies are accepted:
- Senecio jacobaea ssp. jacobaea - the typical plant, with ray florets present.
- Senecio jacobaea ssp. dunensis - the ray florets are missing.
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.
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.
Pollination is by a wide range of bees, flies, 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 200,000, 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.
From medieval times to the mid 20th century, Ragwort was used against inflammations of the eye, for sore and cancerous ulcers, rheumatism, sciatica and gout, for painful joints. According to some, it would relieve the pain of bee stings.
All applications should be external only, never internally, and only under professional supervision.
With the large range of pyrrolizidine alkaloids, which are known to inhibit or reduce cell division, some researchers hope to use them to slow down or arrest the growth of cells in cancer.
In ancient Greece and Rome a supposed aphrodisiac was made from the plant; it was called satyrion.
The leaves can be used to obtain good green dye, as yellow dye is obtained from the flowers, as can be done for brown and orange.
Pests and Diseases
See Senecio for a list of pests and diseases affecting the genus.
- Mowing: Mowing is can be used to prevent reseeding, but leaves the root structure intact and will encourage root growth and spread the plant population in subsequent years.
- Cultivation: Effective on young plants
- Pulling: Pulls easily
- Systemic herbicides (synthetic): Dicamba
- Drench herbicides (synthetic): Sodium Chlorate
- Biocontrols (animal): The Cinnabar Moth Tyria jacobaeae is used as a control for ragwort in countries in which it has been introduced and become a problem, like New Zealand and the western United States. In New Zealand, the ragwort flea beetle (Longitarsus jacobaea) has been introduced to combat the plant.
- Grazing: Toxic to most livestock, with the exception of most, but not all sheep. Grazing is not considered an effective control.