BugLife’s website contains the following information on the toxicity of ragwort to livestock: 

“The toxins (pyrrolizidine alkaloids) in ragwort (sometimes known as stagger weed) can cause liver poisoning. It is a cumulative poison that eventually leads to the rapid onset of symptoms before death, however the symptoms are variable and resemble those of a number of other diseases. Furthermore the diagnosis can only be confirmed by dissection of the liver. The lethal volume of Ragwort is around 7% of body weight for horses and cattle are also prone. Sheep are thought to be less prone to poisoning although it is difficult to find solid evidence of any fatal effects on livestock other than horses.” 

In general, horses, ponies & cattle find ragwort unpalatable, and will not browse on the plant while it is growing unless the site is heavily overgrazed, with not enough other vegetation to support them. Because of this, avoiding overgrazing on areas of permanent pasture should be enough to avoid serious concerns of ragwort poisoning in livestock.  

Once ragwort dies and dries out, it simultaneously becomes much more palatable to livestock, and also contains a much higher quantity of toxins by total mass. Because of this, it is very important to avoid incorporating any ragwort into hay bales when cutting & baling a hay meadow, as livestock will be likely to consume concentrated doses of the alkaloid toxins when they are fed the hay.  

As such, ragwort must be cleared from hay meadows before they are cut and baled. If this is not done, either the hay will be useless and will have to be disposed of (usually by burning), or a hay cut will not take place.  

Neither of these options are at all desirable.  

If a hay meadow is left uncut, the grasses and other vegetation will senesce and go “rank”, dying back and rotting to enrich the soil. This increased nutrient content tends to favour grasses over wildflowers, and the botanical diversity is likely to rapidly decline.  

The hay bales collected from the hay meadows on our nature reserves are used for winter feeding of conservation grazing livestock. When these bales are used to feed livestock on different areas of the reserve, this helps spread a diverse range of wildlflower seeds around the site. It is also a locally sourced, low-carbon option for winter feed, when the grass growth is insufficient to support the livestock required to graze the reserve in the summer months.  

With all this in mind, it also makes very good sense to try and clear ragwort within a 50m distance of the hay meadow, so that large quantities of seed to not constantly enter the hay meadow. 

Ragwort is included in the list of species covered by the Weeds Act 1959. While it is not illegal to have ragwort growing on your land, or even to allow it to spread from your land (a common misconception), a compulsory clearance notice may be issued to landowners who allow the plant to spread onto neighbouring land where it may cause harm to livestock.  

Because of this, it is necessary to clear ragwort within 50m of your land ownership boundary when the neighbouring land is being used to produce hay, or for grazing livestock (in particular, horses, due to their greater sensitivity to ragwort toxicity). As such, preventing the spread of ragwort from our land onto neighbouring agricultural land or horse paddocks is a high management priority for us.   

Another very important consideration is that land in conservation management Agri-Environment funding agreements will usually have certain conditions specific to ragwort about how the land must be managed. A frequent condition is that where land is being managed for the restoration or preservation of species rich grassland, no more than 5% coverage* of the so-called “injurious weeds” - ragwort, dock, creeping thistle - is permitted.  

Managing nature reserves can be a resource intensive, and therefore expensive business, and so obtaining and complying with the conditions of these funding schemes is often essential for their ongoing management.  

This same criteria can also factor into the assessment of the condition of Sites of Special Scientific Interest.  

It is sometimes argued that this criteria is not appropriate, and that a higher percentage coverage of ragwort could be considered tolerable within high quality species rich grassland habitats from a conservation point of view. However, while ragwort may not necessarily pose a serious direct threat to these habitats, high coverages of ragwort may deter graziers from wanting to graze a site, which will lead to rapid deterioration of botanical diversity and habitat quality, and so still poses a very serious, if indirect threat.  

A separate, though related issue, is that the financial implications of non-compliance with Agri-Environment funding schemes would also be extremely serious for any conservation charity, which would again pose a serious threat to the ongoing management of priority habitats on nature reserves.  

* Exactly what constitutes 5% coverage is not rigorously defined here. While it would be possible to use aerial photographs to unambiguously determine the coverage of ragwort on a site, this level of rigour is typically unnecessary. Rather than trying to estimate the exact canopy cover percentage of ragwort, I generally consider the proportion of a nature reserve where ragwort is either dominant or abundant, and use this to guide management decisions. It is also perfectly acceptable to have areas of greater than 5% of the total site area occupied by ragwort where it is present at lower densities. Ultimately, the important factor is avoiding any negative impact from excessive abundance of ragwort, while retaining the conservation benefits from its presence on site, rather than aiming for an arbitrary number. 

Ragwort has a relatively high conservation value for invertebrates, producing many flowers throughout July and August, on which more than 200 species of invertebrates have been recorded (citation – The Wildlife Trust website).  

In moderate quantities, the presence of ragwort on a nature reserve does not have any significant downsides from a conservation point of view. The figure of 5% coverage given above is a reasonable figure below which I would consider ragwort to be a valuable component of a community of grassland species.  

However, as noted earlier, ragwort can be rather invasive, spreading rapidly and becoming very dense. In extreme cases, high densities may be detrimental to other native wildflowers, as the ragwort will compete with them for space, light, water & nutrients.  

This is particularly likely to be an issue when considering areas where species rich grassland is being restored rather than preserved. Restoration of grassland typically involves firstly removing secondary woodland or woody scrub that has encroached into undergrazed areas, and secondly clearing scrub regeneration and maintaining a conservation grazing regime until a closed sward has formed and until the desired level of botanical diversity has been achieved.  

The first step of removing woody scrub tends to leave areas of bare ground, because grass and other species have been completely shaded out by the scrub or secondary woodland canopy. Areas of bare ground are extremely susceptible to colonisation by ruderal species, including ragwort. Where a large seed source of ragwort is present, it is likely to become dominant to the point where it seriously impedes the restoration of the desired species rich grassland habitat.   

It's also worth noting that ragwort sets seed extremely prolifically! While a coverage of approximately 5% in a given year may be desirable, if this is allowed to set seed, it is likely to lead to a much higher coverage in future years. Alternatively, if it is managed by pulling the vast majority shortly before it sets seed, it is likely to persist at around this level of coverage in future years.  

It is difficult to predict what level this coverage will equilibrate to, and this will vary from site to site. In the best case scenario, it may persist as a frequent component of the sward but not become overdominant. In the worst case scenario it may cause reductions in the number and coverage of a number of other rare or protected plant species, with knock on effects for the invertebrates and other species that rely on these. As noted previously, extremely high levels of ragwort can also make it very difficult to find a grazier willing to put livestock on a site, and sustained insufficient grazing pressure constitutes one of the most serious threats to species rich grassland on nature reserves.

When dealing with invasive species, it is always advisable to keep the species under control as much as possible, as managing a small population is much more effective and less resource intensive than attempting to deal with a large population that has become out of control due to insufficient management at an earlier stage. This conservative principle tends to apply throughout conservation land management; for example it is also far better to protect species rich grassland by preventing it from scrubbing over with bramble and hawthorn, than it is to allow this to happen and subsequently attempt to fix things.  

When managing sites with extremely high biodiversity value species rich grassland, it is therefore prudent to try and keep ragwort coverage around or below the 5% level on areas of high quality grassland, and the surrounding 50m from which seed can easily disperse. While we will discuss management options in more detail shortly, this will typically involve pulling the vast majority of ragwort shortly before it sets seed, on an annual basis.  

It’s worth noting that the most appropriate management strategy for ragwort can depend strongly on what habitats are present to start with. In the discussion above we have considered nature reserve quality species rich grasslands, which are a rare, precious and vulnerable habitat in the UK.  

However, if we consider a lower biodiversity value starting point – for example improved grassland (“improved” here denotes “enriched with N/P/K fertilisers” for maximal grass output, rather than an improved species richness) or a ploughed arable field – we may have a much higher tolerance for high quantities of ragwort (where this will not spread onto other more sensitive sites).  

The risk involved in adopting a low-input management strategy here is far lower, as if the ragwort becomes over dominant, it will not be to the detriment of high value habitats and species.  

The Knepp estate’s re-wilding project has been an example of a situation in which ragwort has reached very high levels, due to large areas of bare ground present from a low biodiversity starting point. As a closed sward has established, the levels of ragwort have somewhat equilibrated to a level that is not impacting negatively on the other biodiversity present on the site.  

In general, a more relaxed management approach is appropriate on re-wilding sites with poor starting biodiversity value. For example, a higher tolerance to bramble and woody scrub on grassland areas is likely to be appropriate, as it has biodiversity value but is not threatening existing priority habitats. The same management approaches may not be appropriate to other sites where the starting point is very different, as discussed above. 

Once a decision has been made on the amount of ragwort desired on a site, it must then be managed to maintain this level of coverage. The most common management options are as follows:  

Application of herbicide 

While the use of glyphosate cannot be recommended due to its impact on other flowering plants, citronella is a more targeted herbicide that may be used to kill ragwort, as well as docks and nettles. This can be done using a weed wiper towed behind a vehicle in dense areas of ragwort, provided the sward is grazed down beforehand; however it is not appropriate to use these quantities of herbicide on sites with high botanical interest. Lower densities of ragwort can be spot treated with a knapsack sprayer at the rosette stage. This can be effective, but will be time consuming for larger areas, and even smaller quantities of herbicide usage are best avoided where possible.  

Mechanical cutting 

A tractor and rotary topper can be used to cut large areas of ragwort. If this is done, the cut material must be removed from the site, as if it is left it will dry out, becoming palatable to livestock who may then ingest toxic doses of the dried plant. The most efficient way to do this is by baling the cut ragwort, and removing the bales from the site for composting or burning. While this is an efficient method for dealing with dense areas of ragwort, it has the following drawbacks 1) it is only viable on flatter sites accessible to tractors – many of our best areas of species rich grassland survive only because they are inaccessible to tractors and as such have never been subject to intensive agriculture 2) once cut, ragwort will regrow from the base, flowering and setting seed 3) cutting and baling will remove all other floral interest present on the site, and any grass included in the bales will not be useable to feed livestock over winter. 

Grazing with sheep 

Sheep are less susceptible to ragwort toxicity than horses, ponies, and cattle, and will selectively eat the flower heads off of ragwort, preventing it from setting seed. This can be a very effective method of controlling ragwort on large sites. However, this requires sheep to be on the site during the peak flowering period, and they are likely to browse out a good deal of the floral interest on the site at the same time. High stocking densities may also impact the overall structure of the sward and the invertebrate interest of the site.  

Pulling by hand 

While time consuming, pulling by hand is the best management option. Ragwort can be pulled fairly easily from damp ground, and with the aid of a fork can be removed even from hard dry ground along with the roots. This method has a negligible impact on other flora and invertebrates present on the site, in contrast to the other methods listed here. The main disadvantage of this approach is that it is extremely resource intensive. Every summer, Somerset Wildlife Trust undertakes 50 to 100 person days of ragwort pulling with staff, volunteers & contractors, and this obviously impacts on our ability to carry out other, equally important conservation management work.  

Once pulled, we transport our ragwort off-site, and let it rot down, covering the pile with a tarpaulin to prevent seed from spreading.  

What about cinnabar moths? 

The distinctive black and yellow striped cinnabar moth caterpillars frequently found on ragwort can sometimes strip entire plants of leaves and flowers. If large numbers of cinnabar moths are present on a site, their population will reach some equilibrium with the ragwort. However, this is not a reliable method of control, as populations of both cinnabar moth and ragwort can boom and bust, and ragwort is capable of flowering and setting seed even after being heavily eaten by caterpillars.  

As detailed above, ragwort management is a rather more complex topic than it may first appear, and there are many different factors that need to be considered. While this blog post is not by any means exhaustive, it has covered many of these.  

When deciding on an appropriate management regime, the following broad categories may be useful: 

Hay meadows and land grazed by horses or ponies 

Remove all ragwort plants on an annual basis, with the preferred method being pulling by hand. Clear ragwort on surrounding land to a distance of approximately 50 m to prevent ingress of windblown seed.  

High biodiversity species rich grasslands, grazed with sheep or cattle 

Aim for a coverage of 5% or below of ragwort. The plant provides considerable biodiversity benefits, so it is not desirable to eliminate it altogether. Allowing the coverage to exceed 5% is risky, as it may lead to a negative impact on other rare or desirable plant species, and where land is in Agri-Environment agreements this may risk the imposition of monetary fines. Bear in mind that pulling or other management may be required to maintain ragwort at this level – pulling by hand is the preferred method in this case.  

Lower biodiversity grasslands and “re-wilding” type land 

As long as the levels of ragwort do not appear to be impeding the establishment of other plants, a higher coverage is likely to be tolerated, and will bring benefits for invertebrates on the site. Care should be taken to avoid large quantities of seed spreading onto land in either of the two categories above.