Jeremy Bartlett's LET IT GROW blog

Summer Glory

Memories of glorious summer flowers can brighten up the coldest, darkest winter day.

Today I am thinking about Common Ragwort, Jacobaea vulgaris, which bathes the countryside in its golden flowers in July and August and provides sustenance for many different insects, as well as food for the soul.

Common Ragwort, Jacobaea vulgaris is a native of the British Isles and is indeed common, found in almost every 10km square in England, Scotland, Wales and Ireland, from the Channel Islands in the south to Shetland in the north, up to a height of 1,020 metres above sea level.It is a member of the Asteraceae (Daisy family) and is one of five species of Jacobaea found in in the wild in the British Isles.

Jacobaea vulgaris is so familiar that it is often referred to simply as “Ragwort”, but many of its relatives in the genera Senecio and Jacobaea have English names featuring the word “Ragwort” (note 1).

Where Common Ragwort Grows

Common Ragwort can be found on waste ground, road verges and waysides, on rocks, screes and walls, on sand dunes, in scrub, open woods and along woodland rides. It particularly favours grasslands that are neglected, rabbit-infested or overgrazed.

Outside the British Isles, it is a native plant throughout Europe and in temperate parts of Asia, as far east as Mongolia and parts of China.

Jacobaea vulgaris has been introduced into parts of North America and Australia, parts of North Africa and New Zealand. In North America, it is known as Tansy Ragwort and is thought to have been introduced into Canada in the 1850s in ships’ ballast.

Like several other introduced plants, Common Ragwort is a bit too successful in its new home. (See, for example, my blog post on Shining Crane’s-bill from May 2023.) It is classed as a noxious weed in Australia, New Zealand and Canada and is on the Washington State Department of Agriculture’s prohibited plants list.

How Common Ragwort Grows

Jacobaea vulgaris starts to flower in June and can continue flowering until at least October. Even a couple of weeks ago I found a couple of Ragwort plants in flower while doing a New Year Plant Hunt.

The peak of Ragwort’s flowering season is July and August and it provides a vital supply of nectar and pollen for many of the insects that also peak at this time of year. The feast day of St. James is celebrated on 25 July, and the generic name Jacobaea is named after St. James (Latin Jacobus). One of the English names of Common Ragwort is St. James’ Wort (note 2).

Common Ragwort is a biennial or short-lived perennial. Plants take two or more years to flower, forming a rosette of leaves in their early years. Many of the plants are monocarpic, forming seed and dying after flowering, but some regenerate and flower again in subsequent years, especially where the plant has been damaged or cut, or where the soil is poor (note 3).

Jacobaea vulgaris normally grows about a metre (three feet) in height but can reach 1.5 metres (five feet) tall. Its leaves are deeply pinnately lobed and their ragged shape has led to the name of “Ragwort”. The Wild Flower Finder website describes the leaves as “often reminiscent of the shape of a toilet brush“. It has some lovely photographs of the plant at different stages of growth, as do the Flora of East Anglia and Irish Wildflowers websites. (The Irish name, Buchalan Bui, means “Yellow Boy”.)

After flowering, a Common Ragwort plant produces seeds, each one consisting of an achene with an attached pappus (from Latin pappus, meaning “old man”). This forms a parachute that allows the seed to drift in the wind. The name Senecio is derived from senex (“old man”), after the white fluffy seeds.

The largest Ragwort plants have the most seed, with a few hundred seeds produced by smaller plants and thousands from the largest (note 4).

Common Ragwort seeds that don’t germinate straightaway in autumn or early winter can remain viable in the seed bank for up to 10 years, finally germinating if the soil is disturbed.

Churning up the ground by horses’ hooves will create perfect conditions for seed to germinate. Dry summers can benefit the plant too: at Knepp the drought in summer 2006 and in the following April led to masses of Common Ragwort flowers in 2008 (note 5).

On the Isle of May (in the entrance to the Firth of Forth in Scotland), a storm in December 2011 scorched off a lot of the vegetation with salt spray leaving lots of bare ground. Common Ragwort took advantage of the bare ground and flowered in large quantities in August 2013.

A Great Plant For Insects

Common Ragwort is a very important plant for insects and other invertebrates.

The charity Buglife compiled a list of 61 species of invertebrates (60 species of insect and one mite) that feed on Common Ragwort. Thirty of these species are completely reliant on the Common Ragwort and another 22 make major or significant use of the plant.

The Buglife list omits most of the species of pollinators and nectar feeders that visit the flowers. Adding insects visiting for nectar adds a further 117 species to the count.

The article “Focus on Ragwort” on the Bredfield village blog gives the figure that use Common Ragwort as a home and food source as “over 75 insect species in the UK and over half of these use it as their exclusive food source“.

The Ragwort Myths and Facts website says that “about 150 species of insects, such as bees, flies and butterflies, visit the plant“.

Regardless of the exact numbers of species that rely on it, Common Ragwort has a vital role in supporting Britain’s natural diversity at a time of serious decline.

Unpleasant Smell and Taste

Common Ragwort foliage has a distinctive smell when crushed and this has led to alternative names for the plant such as “Mare’s Fart” in North Shropshire and Cheshire and “Stinking Willie” in Scotland (note 2). Other variations include “Stinking Alisander”, “Stinking Billy”, “Stinking Davies”, “Stinking Nanny” and “Stinking Weed”.

The smell and taste are a warning: Common Ragwort contains toxins. These include at least eight pyrrolizidine alkaloids (jacobine, jaconine, jacozine, otosenine, retrorsine, seneciphylline, senecionine, and senkirkine). The alkaloids are secondary metabolites, compounds synthesised by plants as a defence mechanism against herbivores, insects and pathogens.

When eaten, pyrrolizidine alkaloids can be metabolised into highly reactive pyrrolic esters which can cause damage to liver cells and their DNA.

Concentrations of each pyrrolizidine alkaloid varies widely between plants depending on genetics and growing conditions and each alkaloid has a different level of toxicity.

Common Ragwort is by no means the only plant that contains pyrrolizidine alkaloids and it is estimated that around 6000 species of flowering plants contain these compounds, around 3% of all flowering plants. I’ve already written about a few of them, such as Viper’s Bugloss, Hemp Agrimony and Coltsfoot (note 6).

Ragwort and Humans

Common Ragwort presents no real danger to humans (or dogs for that matter), as its smell and bitter taste would repel even the most determined forager. The Wild Food UK website features Common Ragwort, but as a poisonous plant rather than recommended amuse-bouche.

As the Friends of the Earth Ragwort Mythbuster says “are you really going to eat plate-loads of ragwort any more than foxgloves or other poisonous plants that can be found in Britain’s fields or along paths and verges?”

Common Ragwort must be eaten to cause harm because pyrrolizidine alkaloids are only converted into pyrroles in the digestive system.

Common Ragwort plants can cause dermatitis when the plants are handled roughly or pulled up but this is caused by sesquiterpene lactones. These lactones are found in other plants as well, most frequently in members of the Asteraceae but in the Apiaceae (Carrot family) and Magnoliaceae (Magnolia family) too.

For this reason it is a good idea to wear gloves when handling or removing Common Ragwort. The stems are tough and fibrous to the touch and gloves also prevent abrasions.

Ragwort and Livestock

Common Ragwort is toxic to horses and cattle too, as are many other plants, but sheep and goats are much less affected.

However, I regularly see horses grazing happily amongst Common Ragwort, ignoring the plants entirely. Cattle normally avoid Common Ragwort plants too, unless stocking rates are particularly high (note 7).

As with humans, the smell and bitter taste of fresh Ragwort plants is normally off-putting, so animals choose other vegetation to eat. Because of the doses involved, even if a horse or cow eats an occasional small quantity of Common Ragwort it is unlikely to have a lasting effect on an animal’s health.

 

There is more of a problem is with dried (or wilted) Common Ragwort plants. These lose most of their off-putting smell and taste and livestock will happily eat hay containing Common Ragwort. For this reason Common Ragwort should be removed from fields where hay is going to be cut to feed livestock.

Owners of horses and cattle can minimise the risk of poisoning by avoiding overstocking and overgrazing and ensuring their animals have adequate food at all times. This is should be standard practice, as it is fundamental to the general welfare of the animals.

Briony Witherow writes on the Horse Hub website, “Key steps towards good pasture management include: Avoid over-stocking and overgrazing to minimise compaction, and give grass chance to ‘rest’. This should help to avoid bare patches that give weeds an opportunity to get established. Healthy soil and therefore healthy grass means less weeds”.

For the safety of their animals, many livestock owners remove Common Ragwort from their fields, but there is no need to remove Common Ragwort in places away from horses or cattle.

I think most horse owners would agree with John Shortland, who wrote on his blog  in July 2015: “So should ragwort be controlled or not?  The answer, as with most things in life, is yes but in moderation. It is quite unnecessary to remove ragwort plants from areas of low or no risk as is sometimes thought. I keep horses and spend time each year removing ragwort from the fields in which they graze.”

DEFRA (Department for Environment, Food & Rural Affairs) has a “Code of Practice on How to Prevent the Spread of Ragwort“, which splits land into three categories (note 8).

In the “Low Risk” category, “more than 100 metres from land used for grazing by horses and other animals or land used for feed/forage production”, no immediate action is required to control Ragwort and in uncultivated or semi-natural areas, “wherever possible uncultivated land with low levels of ragwort should remain undisturbed“.

Pyrrolizidine alkaloids and liver damage

Bacteria in an animal’s digestive tract break down some of the alkaloids in plants that it eats but some will travel to the liver. Here, some are metabolised into non-toxic compounds but others form highly reactive pyrrolic esters, which can cause damage to liver cells and their DNA.

The pyrrolizidine alkaloids don’t accumulate in the mammalian body and are excreted in 24 to 48 hours.

Small quantities of the alkaloids will cause small scale damage to the liver but as long as the damage is slight, healthy liver cells can take over the function of the damaged ones. In the longer term the liver has a unique capacity among the body’s organs to regenerate itself after damage.

Large quantities of pyrrolizidine alkaloids (between 5% and 25% of body weight for horses and cattle) can cause far more serious harm, in the form of an irreversible cirrhosis of the liver known as megalocytosis, where liver cells are larger than normal and have markedly enlarged nuclei. (This is because their ability to divide is impaired.)

As mentioned above, Common Ragwort is just one of the plants that contains pyrrolizidine alkaloids and the alkaloids are far from being the only cause of megalocytosis. 

Megalocytosis can also be caused by other toxins (such as aflatoxins, sometimes found in hay and grains), bacterial and viral infections, parasites  and birth defects.

This makes it very difficult to say with absolute confidence that the death of a horse from liver failure was actually caused by pyrrolizidine alkaloids and, if so, by Common Ragwort (note 9).

Deaths from Ragwort

How many livestock deaths are caused by Ragwort? We simply can’t tell.

As DEFRA’s “Code of Practice on How to Prevent the Spread of Ragwort” sums it up: “The scale and extent of illness and death in animals through ragwort poisoning is difficult to determine, as an autopsy would be required in every case to confirm the exact cause of death. There is no current test available to diagnose accurately whether an animal is suffering from ragwort poisoning, and certainly no test to help determine whether any such poisoning relates to ingestion of conserved or live ragwort.”

The number of deaths is probably very low. In June 2005 the Irish Minister for Agriculture and Food stated that “There are no official figures available in Ireland for deaths of horses due to ragwort poisoning. Unofficial estimates indicate that the level is very low and does not warrant any special attention or investigation.”

A report on the Animalweb website, “Ragwort toxicity in the UK (Defra Report 2014)” concludes: “The overall impression from… surveys is that ragwort is a very common weed but only a minority of horse owners spend significant time trying to control it. Despite this ragwort toxicity is an rarely encountered problem in UK horses subject to veterinary care.”

The Ragwort Facts website quotes UK government figures, which give a total number of 13 deaths in 2005 and ten deaths between 2005 and 2010. The website also mentions a French study which found 18 suspected and six confirmed cases in cattle over the period of a decade.

In contrast, the BSBI’s Fermanagh Species account for Jacobaea vulgaris tells us that “as many as 500 equines died from liver disease caused by Common Ragwort poisoning in 2001”. This figure can be traced back to 2003 when John Greenaway (MP for Ryedale) gave the figure in a parliamentary debate on the Equine Welfare (Ragwort Control) Bill. The numbers were “based on known or suspected cases, extrapolated for the whole country“.

Around the same time the British Horse Society claimed that 6500 British horses had died of Ragwort poisoning in 2002. Swansea Friends of the Earth quite rightly took issue with this figure and raised a complaint with the Advertising Standards Authority, which was upheld. (“Horse group told to tone down ragwort campaign”, the Mirror, June 2011.)

Thankfully, current information on the British Horse Society website is more balanced and matches DEFRA’s advice: “The BHS does not advocate blanket removal of all ragwort. The plant plays a significant role in biodiversity, providing a habitat and food for many types of insects, plus pollen for bees. Ragwort has an important place in the British ecosystem in areas away from horse grazing or land used for forage production and should only be removed from high-risk areas“.

There is certainly no need to force the unemployed to carry out unpaid work removing Common Ragwort, as was suggested by Lord Tebbitt in 2014 (note 10).

I think anti-Ragwort hysteria is less prevalent than ten or twenty years ago but every summer comments on social media revive some of the same old horror stories about Common Ragwort.

The “Ragwort, myths and facts” website (with advisors and authors based in the Netherlands, England and New Zealand) and the Ragwort Facts Website were created to counter these myths. The Ragwort Facts website gives a timeline for the campaign of mis-information about Common Ragwort.

Common Ragwort in the Garden

I don’t live anywhere near horses or other livestock so our garden is definitely a “Low Risk” area (note 8).

I am a great fan of Common Ragwort and have introduced it into our garden, where I can observe at close hand its importance for invertebrates. My plants self-seed and young plants appear in patches of bare soil near their parent but I can move or remove them when they’re growing somewhere I don’t want them. (Moving the plants is more successful in winter or early spring, if followed by a good watering to settle in the roots.)

When in flower, a single Common Ragwort makes a lovely statement plant.

Caterpillars of the Cinnabar moth, Tyria jacobaeae, feed on Common Ragwort and its close relatives from May to July. I have rescued them on a couple of occasions – from a meadow where Common Ragwort was being removed and from a grass verge in Norwich which had just been cut. I now have Cinnabar moth caterpillars in the garden every summer and have occasional sightings of the adult moths, which are mainly nocturnal.

Common Ragwort brings me so much delight and, as a beautiful, native plant that supports so many insects, I think it is a terrible shame that it is subject to so much prejudice and misinformation.

I’ll let John Clare have the last word.

As Richard Mabey notes in his book “Weeds”, “Clare’s quiet praise of ragwort perhaps shows how far we have moved from an ecological understanding of weeds” (note 11).

“Ragwort, thou humble flower with tattered leaves
I love to see thee come & litter gold,
What time the summer binds her russet sheaves;
Decking rude spots in beauties manifold,
That without thee were dreary to behold,
Sunburnt and bare– the meadow bank, the baulk
That leads a wagon-way through mellow fields,
Rich with the tints that harvest’s plenty yields,
Browns of all hues; and everywhere I walk
Thy waste of shining blossoms richly shields
The sun tanned sward in splendid hues that burn
So bright & glaring that the very light
Of the rich sunshine doth to paleness turn
& seems but very shadows in thy sight.” – John Clare, “The Ragwort”(1831).

Common Ragwort Gallery

Some more photographs of insects enjoying Common Ragwort flowers:

Notes

Note 1 – The other species of Jacobaea are:

• Silver Ragwort, Jacobaea maritima – introduced from the Mediterranean
• Marsh Ragwort, Jacobaea aquatica – native in marshes and damp meadows and by streams
• Hoary Ragwort, Jacobaea erucifolia – native in England and Wales in grassy places, on banks and field edges but a rare alien in Scotland
• Fen Ragwort, Jacobaea paludosa – very rare native of fenland ditches, in Cambridgeshire.

There are also three Jacobaea hybrids in the British Isles.

For more details see Clive Stace’s “New Flora of the British Isles“ (Fourth Edition, 2019).

When I first learnt plant names, the Asteraceae was still known as the Compositae and Common Ragwort was known as Senecio jacobaea. 

The genus Senecio still exists and more than a dozen species of Senecio in the British Isles include “Ragwort” in their English names. These include plants such as Broad-leaved Ragwort (Senecio sarracenicus), which I wrote about on 14th September 2021. Other members of the genus are known as groundsels, including Groundsel (Senecio vulgaris), the familiar annual weed.

Note 2 – Richard Mabey, pp 375 – 376, “Flora Britannica”. Sinclair-Stevenson, 1996. See also the Plant Lore website.

Note 3 – Studies have shown that between 28 and 44 per cent of plants can re-flower.

“Poole & Cairns (1940), Schmidt (1972) and Forbes (1977) observed that 33%, 28% and 44% respectively of their flowering plants re-grew.”

The references are:

• Forbes, J.C. (1977). Weed Research 17: 387-391.”Population flux and mortality in a ragwort (Senecio jacobaea L.) infestation.”
• Poole, A.L. and Cairns, D. (1940). “Biological aspects of ragwort (Senecio jacobaea L.) control”. Department of Scientific and Industrial Research Bulletin No. 82, Government Printer, Wellington, New Zealand.
• Schmidt, L. (1972). Weed Research 12: 37-45. “Biology and control of ragwort, Senecio jacobaea L. in Victoria, Australia.”

Note 4 – A 1957 study gave figures between 4,760 and 120,400 seeds from plants at eight different sites. The highest total of 174,230 seeds came from a third year plant that had been cut down to prevent it from flowering in its second year. Figures for seed production are generally rounded up and the figure of 150,000 to 200,000 seeds per plant is often quoted.

If every seed grew, our planet would be covered in Common Ragwort in a short space of time but in reality only a small fraction of the seeds produce new plants. Conditions must be favourable for germination, with enough light, not too wet and not too dry. Even seeds that germinate must land in a spot that has enough light and nutrients and it will have to compete with other plants for survival.

Although they are light and equipped with parachutes, most Common Ragwort seeds don’t travel particularly far. Only 0.5% of all seeds that a plant produces travel more than 25 metres and most travel only a few several metres from the parent plant.

The Ragwort Facts website has more data and references to the studies. The first (carried out in New Zealand) looked at the behaviour of around 57 million seeds. The second (conducted in Oregon in the United States) tracked 53,000 individual seeds.

In my own experience I have a single plant three metres away from its parent, with the rest a metre or less away, though these are informal observations rather than a proper scientific study.

Note 5 – Isabella Tree, “Wilding”, Picador, London (2018). Chapter 8, “Living with the Yellow Peril” gives a fascinating account of Common Ragwort at the Knepp rewilding project. The Knepp website’s Injurious “Weeds” Policy is worth a read too.

Note 6 – It is estimated that around 6000 species of flowering plants contain these compounds, around 3% of all flowering plants.

Pyrrolizidine alkaloids are particularly found in members of the Boraginaceae (such as Viper’s Bugloss), Fabaceae (mainly the African genus Crotalaria), and in other members of the Asteraceae.

For more about pyrrolizidine alkaloids, see Moreira R, Pereira DM, Valentão P, Andrade PB (2018). “Pyrrolizidine Alkaloids: Chemistry, Pharmacology, Toxicology and Food Safety.” Int J Mol Sci. 2018 Jun 5;19(6):1668

Note 7 – Where stocking levels are high (five cows per hectare and more) less dominant animals may eat plants that more dominant animals avoid, including as Jacobaea vulgaris. From “Deadly Daisies?” by Gordon Maxwell, on The Biologist website, which includes references.

Note 8 – DEFRA’s “Code of Practice on How to Prevent the Spread of Ragwort” splits land into three categories:

• High Risk – “Ragwort is present and flowering/seeding within 50m of land used for grazing by horses and other animals or land used for feed/forage production”.
• Medium Risk – “Ragwort is present within 50m to 100m of land used for grazing by horses and other animals or land used for feed/forage production”.
• Low Risk – “Ragwort or the land on which it is present is more than 100m from land used for grazing by horses and other animals or land used for feed/forage production”.

Paul Sterry makes a good point when he says of the Code of Practice: “for me the document is oddly schizophrenic: at one turn it conjures up nightmare visions of dead and dying horses – hundreds of them – dropping like flies through ragwort poisoning; and at the other extreme it extols the virtues and value to wildlife of Senecio jacobaea. I may be wrong but it has all the hallmarks of a document written by committee, but a committee whose polarised members could not agree”. (“Guest blog – Ragwort: friend or foe? by Paul Sterry“, 9th July 2019).

The document’s introduction by Rt Hon Alun Michael MP (Minister of State for Rural Affairs and Local Environment Quality and Minister for the Horse) seems to confirm this impression: “The Code is very much a combined effort, reflecting upon the importance of balancing the variety of interests involved. It has been drawn up in consultation with a Steering Group comprising The British Horse Society, Network Rail, English Nature, Wildlife and Countryside Link, the British Beekeepers Association, ADAS and representatives of Local Government. I should like to thank the Group for its efforts. It has not been an easy task to reconcile the different interests and I am grateful for the co-operative spirit shown by the members of the Group“.

Note 9  – Liver failure has a long list of symptoms. These include weight loss, lack of appetite and energy, a dull coat, crusts (in horses, especially on the coronary band), photosensitation, jaundice, and neurological signs, such as staggering, walking in circles, inattentiveness, restlessness, and panicking behaviour. (A rarely used vernacular name for Common Ragwort is “Staggerwort”.)

Note 10 -“‘Make young unemployed pull up ragwort for benefits,’ says Lord Tebbit” is a Guardian headline from October 2014. Lord Tebbitt’s suggestion was, quite rightly, met with scorn. In an opinion piece later the same month, Harry Leslie Smith wrote that “Tebbit shows that Tory cruelty and prejudice run as deep as ragwort roots“. For strict accuracy I should point out that Common Ragwort roots don’t go especially deep.

Note 11 – Richard Mabey, “Weeds: The Story of Outlaw Plants” (2012). Revised paperback edition. Profile Books, London.