It’s poisonous, aggressive and it stinks: ragwort is one of Tasmania’s worst pasture weeds. As well as replacing productive grass and clover, it is highly toxic to some livestock, with horses the most susceptible. Farms, hobby farms, residential land, the bush, roadsides and public land are all at risk from ragwort invasion.
It is for these reasons that ragwort (Senecio jacobaea) is a declared weed under Tasmania’s Weed Management Act 1999, and affected landholders are legally obliged to control it.
Identification of ragwort can be tricky. It is an erect biennial or perennial herb. It has deeply dissected leaves and forms clusters of yellow daisy flowers in summer in the second year of growth. These flowers are about 2.5cm across and are found on the end of upright stems that can reach 1.5m. In the first year of growth, ragwort produces a rosette flat to the ground, which can be hard to detect in pasture. Ragwort resembles a number of other Senecio species, many of which are useful natives; if in doubt, get the plant identified for free by the Department of Primary Industries and Water (62 333 650).
Ragwort is capable of invading a variety of land types, but as it prefers cooler, wetter areas, these are particularly at risk. Small patches of ragwort have persisted in Tasmania for many years, and it is important these infestations are controlled to prevent further spread and damage to the local environment and economy. The light seeds can be transported many kilometres by wind and water – a single plant can affect land elsewhere.
Several biological control agents have been introduced to Tasmania, and these have been very successful in reducing the number and density of infestations. However, other control measures are required to finish the job.
Persistence, timing and method are the key factors in successfully tackling ragwort. Ideally, ragwort seedlings and rosettes should be sprayed in autumn or early spring. A number of herbicides are available that will control ragwort prior to flowering. Once flowering begins, ragwort is difficult to control. Small infestations can be hand-pulled, taking care to remove as much of the root system as possible. As a short-term measure, flower heads can be cut off, placed in secure bags, and left to rot. Larger infestations should also have their flowers removed, but a combination of techniques will be required to eradicate this weed. Download DPIW’s Service Sheet for Ragwort or Contact the DPIW Weed Management Officer in your region to ensure you have the best advice for your situation.