The dangers of ragwort
By Micky Astor
Ragwort is fast becoming the flower of the British road and motorway verge, as it is spread by the traffic and fewer and fewer people control it. It is, however, a menace.
Ragwort (Senecio jacobaea) is an injurious weed and the Government’s Department for Environment, Food and Rural Affairs (Defra) can take action against a landowner who fails to control it, under the Weeds Act of 1959. But as stock farming declines, so less action seems to be taken.
Ragwort contains alkaloids which can accumulate in the liver and can cause death to animals which eat much of it. Livestock tend to avoid it when it is alive, providing they have other sources of food.
The greatest danger is when it is dead and easily ingested in a hay crop. Often, by the time symptoms are noticed, it is too late to save the animal. Cattle and horses are most prone to being poisoned by it, but most stock are susceptible to it, including chickens; sheep and goats are the least affected. Young stock are more vulnerable than mature animals.
Humans who touch a lot of it should wear gloves, as its poison can be absorbed through the skin and is accumulated in the body.
Why is it so pervasive? It is a biennial, taking two years to complete its life cycle (producing a rosette with leaves during the first year, then flowering and dying in the second). On flowering, a mature plant can produce up to 150,000 tiny seeds, which are easily wind blown. Just to exacerbate the problem, each seed can lay dormant in the ground for up to 20 years before germinating! It will only die after it has flowered and seeded, so it can remain thriving in regularly cut grass for years. Hence, any meaningful attempt to control it has to be absolute and relentless.
Poor soil, bare ground, gappy swards, overgrazing, rabbit damage or drought are the major causes of infestation, but a thick sward will often keep it out.
It does have its benefits to wildlife, as a source of nectar. The best known species of invertebrate which feeds on its foliage is the orange and black striped caterpillar of the cinnabar moth. However, it is a poison to mammals and its great ability to spread and linger dormant is reason for everyone to try and control it.
The rosette is quite easily spotted during spring and early summer, once its look, leaf shape and colour have been identified. Its flowering time, during its second or subsequent years, can vary a great deal, but is usually towards late summer. The season can stretch from April to November.
It produces a bright yellow flower, which can be part of a large bouquet. A strong plant can grow up to over a metre in height, or the flower can be on the top of a solitary skinny small stem, only 15 cm high, which makes it hard to eliminate from thicker swards.
The traditional way of controlling it was to pull it up, but this is labour intensive and can leave part of a viable root in the ground for subsequent re-growth.
The best method of control is to spot spray each plant with the herbicide glyphosate. This can be purchased from garden centres under different brand names of products sold to kill green weeds –
- Check the label to ensure it contains glyphosate.
- Be sure to adhere to the directions for its application.
- Watch out for spray drift on to non-target species – obviously on windy days, but also on very hot days, when the spray can vaporise more easily, and drift – and keep it away from water features.
If the concentration is strong, only a few drops are needed on each plant as the chemical is absorbed during photosynthesis (so leave a few hours of sunshine after application) to enter the whole plant and kill it over a period of a week or so. Rain immediately after application will render it ineffective. Glyphosate is also rendered inert on contact with soil.
There is a catch, however, and that is that if a flower has begun to develop on the plant – even during the time it takes for the spray to kill it – it will throw seed and will have beaten you!
The way around this is to cut the flower heads off (they are also easy to spot), put them in a suitable container (a sack or bag), and then spray the remaining plant. Be sure to then burn the flower heads, as if left, even in a sack, they will tend to throw seed.
The new agro-environmental rules for farming mean that there are a growing number of strips of rough grass left around the edge of an arable crop, which is perfect for ragwort to colonise, so now, more than ever, we all need to do our bit in controlling this noxious and pervasive weed.
Further information This will take you to a search page on the Defra website – see note below.