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Ragwort

Posted: Monday 28 July 2014
by James Alexander-Sinclair

Ragwort isn't a very popular plant. In fields and paddocks it's a massive pest as it's extraordinarily toxic to animals.


Ragwort isn't a very popular plant. In fields and paddocks it's a massive pest as it's extraordinarily toxic to animals. A relatively small amount of the stuff - whether alive or dead - can give a horse cirrhosis of the liver, so farmers are constantly alert. Ragwort isn't that toxic to humans, but then very few people are silly enough to try. The ancient Greeks used it as an aphrodisiac (on which subject we will not dwell) and, apparently, the fairies used ragwort to travel to Ireland from the Isle of Arran.

In gardens ragwort is just a slightly annoying weed with particularly strident yellow flowers. On that note, why is it, do you think, that so many weeds are yellow? Dandelions, sow thistles, nipple wort and buttercup, to name a few. It's no accident, I'm sure, because yellow is one of those colours that can catch the eye from a long way away, and if we can see it easily then so can any kind of pollinating insect that happens to be in the area.

No matter how many people dislike this plant, it's universally loved by a whole raft of insects. It provides a cosy hearth and a food source to 77 species of insect, some of which are extremely rare. For example, without ragwort Campiglossa malaris (the picture winged fly), Homocosoma nimbella (the scarse clouded knot horn micro moth) and Thalera fimbrialis (the Sussex emerald micro moth) probably wouldn't be with us. More obviously, the Cinnabar moth is totally reliant on ragwort.

Approximately 117 further species occasionally feed on ragwort. Which only goes to show that even weeds are useful to something, somewhere.





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miles1500 28/07/2014 at 22:25

Didn't realise what this weed was until I saw this blog. I have one plant of it in one of my borders and have been impressed by how attractive the flowers are. The leaves don't look good at all, but apart from that it is adding a great splash of colour.

nutcutlet 28/07/2014 at 22:27

It's the main food plant for the cinnabar moth caterpillars so it's not all bad. 

Bill Ellson 29/07/2014 at 02:34

There is the most astonishing hysteria about ragwort. It is by no means "extraordinarily toxic" to animals. The digstive systems of cattle and horses convert pyrrolizidine alkaloids PAs found in the plant to toxins that damage the animal's liver, but neither cattle nor horses will eat the living plant unless starving because it is extremely bitter. Sheep will eat ragwort without coming to harm and in years gone by farmers would put an old ewe or two in with cattle to control ragwort. It is a real problem if it gets into hay or other feed as the plant loses its bitterness when dried. It is illegal to sell haay containing ragwort. It takes more than "A relatively small amount of the stuff" to harm horses or cattle and the vast majority of ragwort poisonings involve illegal hay or animals being starved.

There are many causes of liver problems in horses and poisoning is just one of them. PAs are just one possible cause of poisoning. PAs are present in many native species. Unfortunately an urban myth has taken hold and many websites publish what they describe as signs of ragwort poisoning, which are in reality the signs of liver failure (however caused).

Sue Bebbington 29/07/2014 at 16:25

The toxic effects of ragwort are extraordinary in that all parts of the plant are toxic, even when dead, also the toxic effect is cumulative such that when an animal shows symptoms treatment is not often successful.

A toxic dose can be can be eaten in one go or little by little over an extended period of time. Ragwort in preserved forage is certainly very dangerous as Bill has mentioned but if ragwort is in grazing it will be come more palatable as it seeds, wilts and dies back.  

Sheep do come to harm if they eat ragwort especially if they are young. Older sheep can tolerate more but are not resistant as such. Ragwort affects a grazing animals, cattle and horses are particularly sensitive to ragwort poisoning and also chickens and pigs. 

Ragwort poisoning is not easy to diagnose even at post mortem and yes liver damage can be due to many causes, but toxic it is and in my opinion keeping it out of grazing land and preserved forage is essential part of good livestock husbandry.

Bill regards this as hysteria, I regard his stance as dismissive of the problem. The fact that he and others aim to repeal the weeds act and ragwort control act may explain his position. These acts only require removal of ragwort where they are likely to spread to grazing land and land used to produce preserved forage so there are still plenty of other areas where ragwort can (and does) flourish.

Anyone who has any concerns about ragwort and animals in their care should speak to their vet

 

Roy Hill 03/08/2014 at 17:50

All I can say is that the field next to my garden which houses a horse of no great immaturity (and occassional grazing cattle and sheep) has had ragwort growing. Last year especially.

I've now got a bit of an over-run area which has ragworts and willowherbs. This year I have a breeding population of cinnabar moth (ragwort obviously) and elephant hawk moth (willowherbs).

Gardens can be used to grow animals as well as plants.

With regards to insects it should be mentioned that insects 'see' at different wavelengths to the human eye, well into ultraviolet ranges. Flowers/plants can have markings which are hidden from human eyesight.

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