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Photo Credit: David Cappaert, Bugwood.org -
Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org -
Photo credit: OSU Extension -
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Several biological controls, including the Cinnabar moth, help control large infestations. -
Cinnabar moth eating tansy ragwort leaves. Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Also known as: Tansy, stinking Willie, tansy butterweed, staggerwort, ragwort, stinking davies, stinking ninny
Tansy ragwort poses a serious threat to livestock. Every part of the plant contains alkaloids that damages livestock’s livers when eaten. This damage is cumulative and irreversible and can kill affected animals. It is a biennial and forms a rosette during its first year of growth before growing a flowering stem the second year.
Description:
| Life Cycle: | Biennial (life cycle lasts two years) |
| Early Detection and Rapid Response species: | No |
| Height: | Up to 6 feet (2 meters) tall |
| Leaf Description: | Leaves are dark green on top and lighter green underneath. The leaves are deeply lobed, giving them a ruffled look. They decrease in size toward the top of the plant. |
| Fruit & Flower Description: | Showy, bright yellow flowers are arranged in a flat-topped clusters. Each flower has numerous daisy-like petals. It reproduces entirely by seed. A single plant can produce up to 150,000 seeds annually. Seeds are small, cylindrical, and topped with feathery appendages that resemble dandelions. |
| Bloom Time: | July to October |
Habitat:
- Tansy ragwort is an opportunistic plant that is often found in vacant lots, yards, pastures, and recently cleared forested areas.
- It prefers cool and wet climates with well-drained soils and full or partial sun.
Impact:
- It contains alkaloids that are toxic to livestock when consumed. All plant parts are toxic, with the highest amount of alkaloids in flowers then leaves, roots and stems.
- Agricultural and hay fields can become quickly overrun by tansy ragwort.
What you can do about it:
- Be sure to wear gloves whenever treating tansy ragwort.
- Never attempt to graze livestock on tansy ragwort.
- Mowing is not recommended. The plant will flower shorter and shorter potentially avoiding the mower blade. Mowing can also spread seeds.
- Small patches can be hand pulled. Make sure to remove the entire root system. May to June is the best time for manual removal. If flowers are present, cut and bag the seed heads to prevent further spread. Place all plant material in a tied plastic bag and dispose of it in the trash – not yard debris or home compost.
- There are several biological controls in Oregon that can help control large infestations. These biocontrol insects are effective at reducing infestations, it is also necessary to combine this strategy with other management practices.
Look-alikes:
Tansy ragwort is often confused with a couple other invasive species: St. John’s wort (Hypericum perforatum) and common tansy (Tanacetum vulgare). Unlike common tansy and St. Johns wort, tansy ragwort’s flowers have numerous daisy-like petals.
Noxious Weed Listing:
| State of Oregon: | Class B, T |
| State of Washington: | Class B |
More Resources:
For a more detailed description, download the Tansy Ragwort Best Management Practices Factsheet
- Pacific Northwest Weed Management Handbook: Tansy ragwort
- University of California, Weed Research & Information Center: Tansy ragwort