Tansy ragwort (Senecio jacobaea) is an invasive weed with a long and deadly history in the Pacific Northwest. In Oregon, it is designated as a Class B invasive weed. It is believed to have been introduced here in the early 1900’s through ballast water from a ship. This plant is native to Europe and Asia […]
Tansy ragwort (Senecio jacobaea) is an invasive weed with a long and deadly history in the Pacific Northwest. In Oregon, it is designated as a Class B invasive weed. It is believed to have been introduced here in the early 1900’s through ballast water from a ship. This plant in native to Europe and […]
Tansy Ragwort, Stinking willie, Staggerwort, Tansy butterweed
Senecio jacobaea (syn. Jacobaea vulgaris)
Tansy ragwort is a tall biennial plant in the sunflower family. It can grow up to 6 feet in height at maturity. The rigid stems of Tansy ragwort are green with an occasional reddish tinge. Plants typically arise from a single stem that becomes branched at the top of the plant, forming flat clusters of bright yellow flowers. The yellow daisy-like flowers have dark yellow to orange centers. Leaves are dark green and ruffled in appearance. Tansy ragwort grows as a rosette in its first year before transitioning into the mature flowering form in its second year of growth. Tansy ragwort can form dense patches, particularly on disturbed sites. This noxious weed is dangerous to humans and livestock due to a poisonous alkaloid (hepatotoxic pyrrolizidine) in its tissue which causes liver damage when ingested.
3-6 feet
Yellow
July to September
From a distance, tansy ragwort can look like common St. John’s wort (Hypericum perforatum), but upon looking more closely, tansy ragwort has large ruffled leaves, whereas St. John’s wort has many small leaves. Also, tansy ragwort has flowerheads with 13 petals, while St. John’s wort has 5.
Tansy ragwort is opportunistic plant often found in disturbed areas. Tansy likes a cool and wet climate, well drained soils and full to partial sun. Patches are found in pastures, fields, grasslands, vacant land, waste places, horse trails, roadsides, rangeland, riparian areas, forested areas, and clear cuts. Areas of greatest concern are improperly managed pastures and disturbed areas.
Prolific in pastures, clear cuts, and disturbed roadside areas, tansy populations can become quite dense. The leaves are toxic to cattle and horses, causing irreversible liver damage. In the 1960’s and 70’s livestock losses in Oregon amounted to 5 million dollars a year. Unlike cattle and horses, sheep appear to be unaffected by ragwort’s toxicity. Once considered Western Oregon’s most economically serious noxious weed, biological controls have reduced the severity of outbreaks below economic threshold levels.
Eurasia
Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
The WeedWise Program has finalized Best Management Practices for controlling Tansy Ragwort. Check out this comprehensive guide today.
Tansy Ragwort, Stinking Willie, Staggerwort, Tansy butterweed
Senecio jacobaea (syn. Jacobaea vulgaris)
Tansy ragwort is a tall biennial plant in the sunflower family. It can grow up to 6 feet in height at maturity. The rigid stems of tansy ragwort are green with an occasional reddish tinge. Plants typically arise from a single stem that becomes branched at the top of the plant, forming flat clusters of bright yellow flowers. The yellow daisy-like flowers have dark yellow to orange centers. Leaves are dark green and ruffled in appearance. Tansy ragwort grows as a rosette in its first year before transitioning into the mature flowering form in its second year of growth. Tansy ragwort can form dense patches, particularly on disturbed sites. This noxious weed is dangerous to humans and livestock due to a poisonous alkaloid (hepatotoxic pyrrolizidine) in its tissue which causes liver damage when ingested.
Tansy ragwort leaves are evenly spaced and alternate along the stem. Leaves decrease in size toward the top of the plant. Leaves can be smooth, or lightly hairy on their underside of lower leaves. Leaves are dark green and generally lighter on the underside. The leaves of Tansy ragwort are pinnate and appear to be ruffled in appearance.
Tansy ragwort has bright yellow, showy flowers forming a flat-topped cluster at the end of the stem. There can be anywhere from 20 to 60 flowers in a cluster. The daisy-like flowers have numerous disc flowers surrounded by 10-15 evenly spaced ray flowers. Peak flowering occurs from July to September.
Tansy ragwort produces very small, cylindrical seed like fruits called achenes. The achenes from the ray flowers are smooth while the achenes from the disc flowers are hairy. The achenes have a dandelion-like set of bristly hairs called a pappus which aids in dispersal of the seed by the wind. Adult plants can produce up to 200,000 seeds. Seeds can remain viable in the soil for more than 10 years.
The root system of tansy ragwort consists of a distinct taproot or crown with lateral and secondary roots spreading away from the plant. Roots can reach 1 foot deep into the soil. New root shoots are easily formed if a plant is mowed, cut, or injured.
Tansy ragwort reproduces predominantly by seed, but in some instances can also spread vegetatively. Seeds are dispersed by wind or by wildlife. Seeds can also be transported by machinery, contaminated soil and hay, and boots and clothing.and by seed. Vegetative reproduction occurs when roots or the crown are injured and new shoots develop. The fragments from the injured roots can generate new shoots.
Tansy ragwort is opportunistic plant often found in disturbed areas. Tansy ragwort likes a cool and wet climate, well-drained soils and full to partial sun. Patches are found in pastures, fields, grasslands, vacant land, waste places, horse trails, roadsides, rangeland, riparian areas, forested areas, and clear cuts. Areas of greatest concern are improperly managed pastures and disturbed areas.
Native to Eurasia, tansy ragwort was first reported in the United States in California in 1912. In Oregon, tansy ragwort was believed to have been introduced through contaminated ballast in the early 1900s (Christy et al., 2009). The first documented herbaria record for tansy ragwort is from Multnomah county in 1922. Since becoming established it has spread across western Oregon.
Tansy ragwort can be found throughout Clackamas County. It is very widespread and directly impacts properties throughout the county. As a ubiquitous weed, this is not a species that is actively surveyed. Mapped distributions do not represent the full extent of the tansy ragwort population in Clackamas County.
The management of invasive weeds is best served through a process known as Integrated Pest Management (IPM). IPM is a weed management methodology that utilizes:
An IPM based strategy ensures the maximum effectiveness of treatment measures. IPM strategies typically use more than one management method to target one or more susceptible life stages. It is adaptive to site conditions in the field and to the response of a plant to management. The utilization of multiple management tools also inherently reduces the use of herbicides in a management plan. The IPM process ultimately provides a framework for the establishment of Best Management Practices (BMP) which outlines the best approach for controlling a particular weed infestation.
Tansy ragwort can be effectively controlled by biological, chemical, and manual methods. It is an important plant to control, especially in hay and pasture lands, where it can harm grazing animals. As with any control method, it is important to avoid disturbing the soil as much as possible. Soil disturbance can bring buried seeds to the surface, and lead to increased soil erosion. Due to the toxicity of tansy ragwort, be sure to wear gloves and protective clothing when removing this plant.
Tansy ragwort can be controlled by digging or pulling. Plants should ideally be pulled between May and June, after they bolt and before they flower. Pulling and digging is easier when the soil is moist. Later in the season, soils dry and harden making tansy ragwort plants much more difficult to remove. Rosettes should be dug up, removing as much as the root as possible. Grubbing tools, hoes, and shovels can be used.
Mowing is not a suggested means of control for tansy ragwort. While mowing may prevent the plant from immediately producing seeds, it also stimulates additional vegetative growth. This leads to more plants and more stems per plant in the same season. Mowing is especially problematic in pastures, where it can spread the toxic leaves making it harder for grazing animals to avoid.
Grazing of Tansy ragwort is generally discouraged. For most grazing animals, the plant is highly toxic. Sheep are known to tolerate the alkaloids, but tansy ragwort is not considered desirable forage. The impacts of grazing on tansy ragwort is similar to mowing, and may help to suppress the plant, but is not an effective control method.
Herbicide application is an effective means to control tansy ragwort infestations. Tansy ragwort is susceptible to several systemic herbicides. Be cautious when using herbicides on pasture land with grazing animals.
Product Names: Several names
Rate:
1 to 2 lb acid equivalent per acre
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Re-treatment may be required to achieve effective control. 2,4-D is a broadleaf selective herbicide and not will harm grasses. Use care when working around desirable plants to avoid damage. Leaves should be sprayed until wet but not dripping to achieve good control.
Product Names: Banvel, Clarity
Rate:
1 lb acid equivalent per acre
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Re-treatment may be required to achieve effective control. Dicamba is a broad-leaf selective herbicide and not will harm grasses. Use care when working around desirable plants to avoid damage. Leaves should be sprayed until wet but not dripping to achieve good control.
Product Names: Weedmaster, Pasturemaster
Rate:
2 qt per acre
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Re-treatment may be required to achieve effective control. 2,4-D & dicamba are broadleaf selective herbicides and not will harm grasses. Use care when working around desirable plants to avoid damage. Leaves should be sprayed until wet but not dripping to achieve good control.
Product Names: Crossbow
Rate:
1.5 to 2 quarts per acre
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Re-treatment may be required to achieve effective control. Triclopyr & 2,4-D are broadleaf selective herbicides and not will harm grasses. Use care when working around desirable plants to avoid damage. Leaves should be sprayed until wet but not dripping to achieve good control.
Product Names: Escort
Rate: 0.75 to 1 oz per acre (0.45 to 0.6 oz acid equivalent per acre)
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Metsulfuron is primarily active against broad-leaf plants and generally will not harm grasses. Use a surfactant to increase effectiveness.
Product Names: Milestone
Rate: 4 to 5 fl oz per acre (1 to 1.25 oz acid equivalent per acre)
Time: Apply in late fall through spring (November through April) after seedlings have emerged and before rosettes have bolted.
Comments: Aminopyralid is broadleaf selective herbicide. Use a surfactant to increase effectiveness. Do not compost manure or vegetation from treated sites.
Tansy ragwort is a great example of biological control success. Three different insects are currently used to target tansy ragwort and have shown to greatly reduce populations in Oregon. While effective, biological control methods will never result in the complete eradication of a weed. Control of Tansy ragwort using biological controls can also take several years. As such, the use of biological controls should be combined with manual or chemical control methods when working in hay or pasture lands to prevent livestock poisoning. Populations of all biological controls will vary from year to year, so the occasional resurgence of tansy ragwort should be expected, particularly in years with very wet springs.
Pulled or dug up plants should be removed from pastures and hay fields. Plants should be bagged and disposed of as garbage. For large infestations, plants may be removed from the field, piled, and covered in an area inaccessible to livestock. Care needs to be taken to prevent dispersal of seed, as seeds can develop even after pulling.
Tansy ragwort control is manageable. Follow up treatments are necessary and continued monitoring of sites is needed. Seeds may persist in the soil for years following treatment. If animals have been in a field where tansy is present, isolate animals for a few days to prevent the spread of seeds.
Tansy Ragwort Management Timeline
 Currently
Clear
Tomorrow is forecast to be Much Cooler than today. Morning showers.
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 Wednesday
50%
Chance of Rain
Showers late. Lows overnight in the upper 40s.
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Thursday
60%
Chance of Rain
Showers in the morning, then cloudy in the afternoon. High 58F. Winds S at 5 to 10 mph. Chance of rain 60%.
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 Friday
80%
Rain
Partly cloudy in the morning then becoming cloudy with periods of rain later in the day. High 57F. E winds shifting to S at 10 to 15 mph. Chance of rain 80%.
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