Vectors of Spread:
General: Tansy Ragwort (Senecio jacobaea) is a biennial or short-lived perennial that can be found throughout Southern British Columbia. It was first seen in North America in the 1900’s and is believed to have been spread by contaminated hay.
Flowers: Bright yellow, daisy-like flower heads that are arranged in dense, flat topped clusters near the top of the stem. Each flower has between 10-15 ray-like petals that surround a yellow-orange center.
Stem: Mature plants range from 0.2 m – 1.2 m in height with one or several upright stems that branch out near the top.
Leaves: A low rosette is produced during the plant’s first year with dark green, ruffled (lobed) leaves on purplish stems. Second-year flowering stems are alternate, dark green on top with whitish-green underneath, with deeply cut, blunt-toothed lobes and a ragged, ruffled appearance. Basal leaves are stalked, 4 – 20 cm long, and 2 – 6 cm wide.
Seeds: Ribbed seeds are 1 mm long with a pappus, or cluster of white hairs, about 3 mm long.
Roots: Each plant has a fibrous system of coarse, light-coloured roots that can produce small, adventitious shoots.
Common Tansy (Tanacetum vulgare): Perennial species that reproduces by seed and can grow up to 1.8 m in height. Common Tansy has many yellow, disc-shaped flowers that are found at the top of the plant in flat-topped clusters.
Common Tansy prefers to grow in sunny areas with well-drained soils and cannot establish in frequently tilled soils.
St. John’s Wort (Hypericum perforatum): Perennial that grows to about 1 m in height. St. John’s Wort has showy, bright yellow flowers with 5 petals that turn rusty red when they mature. It prefers dry, sandy soils and grows in full sun.
Habitat and Origin
- Tansy Ragwort was introduced to North America in the 1900’s and was brought over from Europe and spread in contaminated hay.
- It is most often found in disturbed sites and on bare ground in grazed pastures, roadsides, vacant non-crop lands and on forest clear-cuts.
- Tansy Ragwort thrives in full sun or partial shade with well-drained soil. It is not commonly found in areas with high water tables or acidic soil.
Propagation and Vectors of Spread
- Tansy Ragwort spreads primarily by seeds, as they get carried off by the prevailing winds. Seeds may also be spread by people, water, animals, and livestock. Tansy Ragwort seeds are also transported in soil being carried by equipment or vehicles. This species’ seeds can remain viable for up to 15 years depending on their depth.
- Tilling, grazing or other disturbances will cause dormant seeds to germinate. Plants that go to seed will die at the end of the season.
- Regeneration of shoots can also occur from crown buds, root fragments and intact roots. As with the seeds, disturbance or injury to shoots promotes vegetative propagation.
Economic and Ecological Impacts
- Contains alkaloids that are toxic to cattle, deer, pigs, horses and goats
- In susceptible animals, liver damage is possible due to cumulative ingestion
- Can reduce overall productivity and stockign levels in areas utilized by livestock
- Toxic to livestock
- Can taint honey produced by bees due to the alkaloids in Tansy Ragwort, making it off-coloured and too bitter to market
What Can I Do?
The best approach to controlling the spread of Tansy Ragwort is PREVENTION.
Learn to identify Tansy Ragwort: use the images presented in this profile page to learn how to identify Tansy Ragwort
What to do if you spot it: You can report any Tansy Ragwort sighting by clicking here.
- Regularly monitor properties for weed infestations.
- Ensure soil and gravel is uncontaminated before transport
- Quickly re-vegetate disturbed areas with fast-growing competitive, native plants can limit growth of Tansy Ragwort and is a fundamental tool to limit it.
- Minimize soil disturbance in area surrounding infestation
- Ensure plants (particularly flowering heads or root fragments) are bagged or covered to prevent spread during transport to designated disposal sites (e.g. landfill).
- Plant Tansy Ragwort in a garden, no matter how well-contained its enclosure may seem.
- Move soil that has been contaminated with Tansy Ragwort.
- Unload, park, or store equipment or vehicles in infested areas; remove plant material from any equipment, vehicles, or clothing used in such areas and wash equipment and vehicles at designated cleaning sites before leaving infested areas.
Only effective on established stems if the root system is entirely removed or frequently cultivated (tilled), which prevents the growth of seedlings and root sprouts. Repeated heavy cultivation can be used as a control technique and frequent mowing before flowering can prevent seed production. Hand pulling is only effective in small infestations and if root is completely removed.
The use of a wick or selective spot spraying is recommended to minimize non-target damage. Effective herbicides include dicamba, 2,4-D, picloram, and picloram + 2,4-D. Spring or mid-summer applications of 2,4-D are most effective at managing young seedlings and rosettes, while dicamba/dicamba + 2,4-D are more effective on advanced growth stages.
Note that picloram is not suitable for wet coastal soils.
We recommend that any herbicide application is carried out by a person holding a valid BC Pesticide Applicator Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations, and site-specific goals and objectives.
Defoliating moths (Tyriah jacobaeae), root feeding beetles (Longitarsis flavicorni, L. jacobaeae), and seed head flies (Hylemya seneciella) have been effective in biologically controlling Tansy Ragwort in places such as the Fraser Valley.
Invasive Species Council of BC, Tansy Ragwort Info Page, https://bcinvasives.ca/invasive-species/identify/invasive-plants/tansy-ragwort
Invasive Species Council of BC, TIPS Factsheet, Tansy Ragwort, https://bcinvasives.ca/documents/Tansy_Ragwort_TIPS_Final_08_06_2014.pdf
King County Government Page, Tansy Ragwort Identification and Control, https://www.kingcounty.gov/services/environment/animals-and-plants/noxious-weeds/weed-identification/tansy-ragwort.aspx