Species specifics: Tansy ragwort

Fast facts

Noxious biennial weed commonly found throughout the Pacific Northwest.
Highly toxic and lethal to livestock, especially horses and cattle, which typically cannot recover after consumption.
Gangly weed averaging 1 to 4 feet tall that blooms yellow flowers in a flat-topped canopy in late spring.
A member of the sunflower family that is sometimes referred to as stinking willie or staggerwort.

What to look for

Tansy ragwort (Jacobaea vulgaris), also known as stinking willie or staggerwort, is a noxious biennial herbaceous weed found throughout the Pacific Northwest that is highly toxic to livestock, dogs and humans.

Averaging 1 to 4 feet tall, tansy ragwort is a notably weedy-looking plant with ragged dark green stems and a canopy at the top that can grow up to 6 feet in ideal conditions. The weed first establishes itself as a ground rosette with basal leaves that will overwinter in that stage until bolting in the spring. Tansy ragwort leaves are ruffled and dark green and will develop a flat cluster in the upper canopy that blooms yellow flowers in late spring to early summer. In mature plants, the stems can sometimes have a reddish tinge.

Each tansy ragwort plant can produce up to 150,000 hardy seeds that can remain viable for up to 10 years. While it is a biennial under normal conditions, because of its hardy and prolific seed- producing nature, when mowed, it will act more like a short-lived perennial in succeeding years.

The entire plant is extremely toxic to livestock, dogs and humans, with cattle and horses most severely affected. In general, animals do not find the weed palatable and will consume it only when other food sources are scarce or through infested stored forages. At doses likely to be ingested, infected animals rapidly develop chronic liver disease, almost always resulting in death not long after consumption.

Where it is found

Primarily along the West Coast, including Northern California, Oregon and Washington, but has also been reported in the New England states and western Montana. Tansy ragwort grows in cool climates that receive more than 20 inches of annual rainfall or in heavily irrigated locations in well-drained soils. Because of its aggressive spreading tendencies and lethal toxicity, tansy ragwort is a noxious weed of high management importance in nearly every state where it is found.

How to treat it

Treat tansy ragwort infestations in spring before flowering or in fall while young plants are still in the rosette stage with a broadcast foliar application using HighNoon® herbicide at 20 fluid ounces per acre or GrazonPD3™ herbicide at 24 to 42 fluid ounces per acre.

GrazonPD3™ is a Restricted Use Pesticide. GrazonPD3 is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. GrazonPD3 is not for sale, distribution or use in Nassau and Suffolk Counties in New York State. Under normal field conditions, HighNoon® is nonvolatile. HighNoon has no grazing or haying restrictions for any class of livestock, including lactating dairy cows, horses (including lactating mares) and meat animals prior to slaughter. Label precautions apply to forage treated with HighNoon and to manure and urine from animals that have consumed treated forage. Consult the label for full details. HighNoon is not registered for sale or use in all states. Always read and follow label directions.