According to the Invasive Plant Council Of BC: Tansy ragwort (Senecio jacobeae) is a poisonous plant that was likely introduced to North America as a medicinal herb. It has since invaded pastures, woodlands and waste areas throughout the South Coast of BC, including central and northern Vancouver Island.
When this plant gets into fields used for feed, it can reduce the available quantity by fifty percent. It is also poisonous to livestock like goats, cattle and horses. Toxins can build up over time, so it only takes trace amounts to eventually poison the animal. Honey collected in areas of high concentrations of the plant can poison people as well. The highest concentrations of the toxin can be found in the flower heads.
The damaging effects of this plant can be reduced through good and effective biological control options and public awareness. this plant should be allowed to get established in an area, and if it does, do not let it go to seed.