The Noxious Weeds Act of 1936 sought to control the spread of three native plants – namely thistles, docks and ragwort (Senecio jacobaea) – that were regarded as a threat to the viability of Irish agriculture. In the case of the latter, the threat manifested itself in ragwort’s known toxicity to livestock, particularly cattle and horses. In the 1930s, the bulk of agricultural work was carried out by horses, so any threat to the well-being of horses, potentially would impact on agricultural output as well.
If eaten in quantity, various alkaloids in ragwort result in the accumulation of copper in the liver, causing illness and possibly death in the animal afflicted. Cattle and horses will generally avoid ragwort growing in pasture, but may eat it if food is scarce or when contained within silage or hay.
The level of one-off fatal dose appears to vary widely, with fatalities typically occurring at between 3 percent and 7 percent of body weight equivalent ingested over 24-48 hours. Even at lower doses, irreparable liver damage can occur, and this damage is cumulative over time as more and more of the liver becomes affected. However, there appears to be no evidence that small doses ingested over long periods of time cause damage, as the alkaloids themselves are quickly flushed though the digestive system.
Ragwort is not particularly a nuisance in the domestic garden, as it is easily removed by pulling, and only proliferates over a number of years when conditions are favourable and control minimal. The most troublesome common garden weeds tend to be those that spread quickly from small pieces of root, and/or by runners, as well as by seed, such as ground elder, silverweed or creeping buttercup.
Nevertheless, from an animal-husbandry perspective, control of ragwort is desirable. Most at risk are horses, as they have a long life thus increasing the risk of cumulative liver damage.
When the Noxious Weeds Act of 1936 came into force, landowners who failed to control plants covered by the legislation faced fines of up to £20, which was a considerable sum of money at the time, twice the average price of an acre of land and five times the price of a calf.
Although the legislation is still in force, the level of fine that can be imposed remains in a 1930s time-warp. The only redeeming feature of the original legislation is that the Ministry of Agriculture may enforce the removal of ragwort from infested land, and seek recovery of any expenses incurred from the landowner. Ironically, the land most infested with ragwort these days is rarely agricultural land but more typically roadside verges under the control of municipal authorities or ‘development’ land (and particularly abandoned development land).
Control of ragwort
Given that one ragwort plant has the ability to produce up to 200,000 seeds, it makes sense to cut down or remove the plant before seed release takes place – generally late July to mid September. A plant prevented from seeding may stay alive till the following year when it will produce a new flower head so physically removing the plant is better than simply cutting down the flower head. Some parts of the plant may remain in the soil and re-emerge the following year; also fresh plants may develop from seed already in the ground. Seeds remain viable for a number of years.
However, with some vigilance and good neighbourly endeavour, the ragwort population could easily be reduced to tolerable levels over a period of two or three years. Cut or pulled-up plants should be disposed of in a way that ensures they won’t be eaten by grazing animals. Rather than seeking enforcement of archaic and outdated legislation, a more diplomatic approach would be to discuss ragwort with neighbouring landowners, and perhaps even offering to help them control it.
The final point is that ragwort is not an alien species, but part of Ireland’s rich native heritage. Historically, ragwort has been used medicinally for inflammation, ulcers, rheumatism, sciatica, gout and painful joints, and supposedly has aphrodisiac properties. However, owing to its toxic nature, self-medication is strongly discouraged!
The leaves of ragwort yield a fine green dye, while brown, yellow and orange can be obtained from the flowers. Ragwort may also have a role in reducing levels of heavy metals in land contaminated by the dumping of industrial waste.