Latin Name: Jacobaea vulgaris
Physical Description: it is a biennial or short-lived perennial herb from a poorly-developed to evident taproot. Stems are erect, sparsely to densely white woolly-hairy, branched towards the top and grows up to 1.2 meters tall. Leaves are alternate, deeply lobed giving them a ruffled appearance, and dark green in colour. Heads of usually 13 yellow ray and numerous yellow disc flowers are located in flat-topped clusters. The bracts surrounding each head are black-tipped and in a single row.
Habitat: it inhabits drier environments, avoiding wetlands and acidic soils. It can commonly be found growing in grasslands, pastures, rangelands, fields, clear-cuts, roadsides, railway right of ways and other disturbed areas.
Impacts: it out-competes native plants, reducing overall biodiversity. It also results in a decrease in pasture productivity. It is toxic to livestock and can result in liver damage in susceptible animals. Although most animals avoid the plant, it is inadvertently consumed in contaminated hay. Bees that forage on tansy ragwort may produce honey that is bitter and off-color.
Reproduction: it reproduces mainly by seed, but can also reproduce by vegetative growth if roots are damaged or severed. A single plant can produce up to 150,000 seeds that can remain viable in the soil for up to 20 years.
Mechanical: small populations can be removed by manual digging as long as entire root mass is removed. Mowing before flowering can prevent seed production, but may stimulate root growth. Repeated mowing or heavy cultivation that prevents the growth of root sprouts is effective to manage the population.
Chemical: Several herbicides with the following active ingredients can control Tansy ragwort: glyphosate, 2, 4-D, aminopyralid, chlopyralid, picloram, dicamba, imazapyr, metsulfuron, and triclopyr. For available products, contact your local agri-supply store. Prior to any herbicide application, read and follow the label instructions.
Biological: Several weevil species are established in British Columbia as biological controls:
- Longitarsus jacobaeae– root feeding flea beetle
- Tyria jacobaeae– foliar feeding moth