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Photo Credit: David Cappaert, Bugwood.org -
Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org -
Several biological controls can be used to control large infestations. 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 cause damage to livestock’s livers when ingested. 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 on the underside. 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 cluster at the end of the stem. Each flower has numerous daisy-like petals. It reproduces almost entirely by seed with a single plant producing 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 pyrrolizidine 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.
What you can do about it:
- Be sure to wear gloves whenever treating tansy ragwort.
- Mowing is not recommended, as the plant will flower shorter and shorter potentially avoiding the mower blade. Mowing can also spread seeds.
- Small patches can be hand pulled, making 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 that can help control large infestations.
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:
Download the Tansy Ragwort Best Management Practices Factsheet
- Pacific Northwest Weed Management Handbook: Tansy ragwort
- University of California, Weed Research & Information Center: Tansy ragwort