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. Tansy ragwort is a biennial and forms a rosette during its first year of growth before bolting 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) |
| Leaf Description: | Leaves are dark green on top and lighter green on the underside. The leaves are evenly spaced and alternate along the stem. 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 12 or 13 daisy-like petals. It reproduces almost entirely by seed with a single plant producing up to 150,000 seeds annually. |
| Bloom Time: | June to October |
Habitat:
- Tansy ragwort is an opportunistic plant that is often found in disturbed areas, pastures, poorly managed grazing areas, and recently cleared forested areas.
- It prefers cool and wet climates with well-drained soils and thrives in full or partial sun.
Impact:
- Contains pyrrolizidine alkaloids that become toxic in livestock after ingestion. All plant parts are toxic, with the highest amount of alkaloids in flowers then leaves, roots and stems.
- Can cause liver damage in humans and should never be used as an herbal remedy or tea. It can also contaminate hay, milk and honey.
What you can do about it:
- Mowing is generally not recommended, as the plant will flower shorter and shorter potentially avoiding the mower blade.
- Small patches of tansy ragwort can be hand pulled, making sure to remove the entire root system. This is best done in May to June before it flowers and before the soil dries out. If flowers are present when removing it, cut and bag the seed heads to prevent further spread.
- Be sure to wear gloves when pulling tansy ragwort to avoid cause skin irritation.
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 12-13 daisy-like petals.
Noxious Weed Listing:
| State of Oregon: | Class B |
| 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