Image by Hannah Stoakes
Even if you don’t recognize the name, you have almost certainly seen this plant growing along roadsides throughout Pender Island! Tansy Ragwort (Jacobaea vulgaris) is a highly invasive plant that originated in northern Europe and has spread to many places in Southern BC. It can be identified by its bright yellow, daisy-like flowers arranged in dense, flat-topped clusters atop purplish stems.
While it may look pretty, this plant packs a nasty punch! It grows aggressively on open, disturbed sites and produces up to 150,000 seeds per plant, which are easily transported to new locations by the wind. These seeds can survive in the soil for up to 15 years! As an invasive plant, Tansy Ragwort easily outcompetes native wildflowers that are necessary food sources for our native pollinators.
On top of the ecological risk it poses, all parts of the plant are highly toxic and pose a significant health risk to livestock that graze on it. Due to this risk, biocontrol agents such as the Cinnabar Moth and Ragwort Flea Beetle, whose larvae feed on the Tansy Ragwort plant, were introduced from Europe into the U.S. to try to manage its spread. While these projects have seen some success, the full ramifications of these biocontrol agents are not well understood. Further distribution of the Cinnabar moth is discouraged in many areas, as it had been noted to feed on related native and horticultural species of ragworts and groundsels.
Removal of Tansy Ragwort once it is well-established is extremely difficult, so it is important to undertake coordinated efforts to manage its spread into new areas. Right now you can help to minimize spread! Flowers can be removed before going to seed. Flower heads can still generate seeds after they are cut, so they should be bagged, sealed and labeled “Invasive plant” for disposal at the Hartland landfill or incinerated at a more appropriate time. Care should be taken not to spread seeds during transport.
If the plant is pulled before flowering, it can be left on site to decompose, in areas where livestock will not eat it. Hand pulling is typically only effective for small infestations, however, a containment line can be established between infested and non-infested areas on larger properties so that new populations of the plant can be easily identified and removed as they appear. Only remove the plant if you are able to remove the entire root system, as new growth can be stimulated by mowing, grazing, or poor hand removal. This is easiest to do in the spring when the soil is moist and before the plant has gone to flower. It is important to minimize soil disturbance in affected areas and to reseed with native competition as soon as possible.
Kassidy Kelly - Conservation Interpreter and Technician, Pender Islands Conservancy