Weed Of The Month: Common Tansy
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Weed of the Month: Common Tansy
Allison Kosto
MSU Broadwater County Extension Agent
This weed of the month has a long history of medicinal use, until it became a major problem along roads, pastures and disturbed areas. This weed is Common Tansy.
Description & Habitat
A native of Europe, common tansy, was introduced to North America for use as a folk remedy and ornamental plant. History of this plant dates back to the colonial herb gardens in the 1600s. It was first documented in Montana in 1931 in Madison County. It can now be found throughout Montana, including Broadwater.
It’s fairly easy to identify with its yellow button-like flower heads. They form dense, flat-topped clusters at the ends of the stems. It is a perennial that can grow up to five feet tall. In a mature plant, leaves have a fern-like appearance that produces a strong odor. The stems and flowers grow in clusters, giving it a bush-like appearance. It’s a later-flowering plant occurring from July to October. It spreads both by seeds and rhizomes (creeping roots). The plant has a shallow root system that is very competitive with other plants for water and nutrients.
Common tansy contains alkaloids that are toxic to both humans and livestock in large quantities. However, livestock poisoning is rare because it is unpalatable and unappealing to them. Toxicity to humans typically happens through long-term use. There have been reports of illness associated with handpulling the plant by absorbing toxins through the skin. Additionally, common tansy can reduce forage for livestock and wildlife and reduce plant diversity.
Management
Common tansy is a Montana Noxious Weed, which means you are required to control it if it’s on your property. You can play a role in reducing the spread of seeds. Do not drive or walk in heavily infested areas if possible. Wash vehicles, ATVs and equipment before going home. Purchase only certified noxious weed seed-free hay.
Because of its rhizomatous root system, mowing or hand-pulling is marginally effective. Mow during bud stage for best results. Wear gloves and protective clothing when pulling to prevent absorbing toxins through the skin. The plant is unpalatable to cattle. Some research suggests that sheep can be effective if used season-long, but long-term effects of the sheep’s health need to be studied further. There are currently no biological control agents for Common Tansy.
Use of chemicals can be effective, especially in an integrated pest management system. Commonly used chemicals include Chaparral, Cimarron, Escort, Telar and Tordon (restricted use). Always read and follow the entire label when applying herbicides. Common chemical names are used for clarity but does not imply endorsement of a product or brand.
For assistance with weed identification and control, contact the MSU Extension Office in Broadwater County at 406-266-9242 or allison.kosto@montana.edu.
Broadwater County has a cost-share program for controlling noxious weeds, including dalmatian toadflax. For more information, contact the Broadwater County Weed District at 406-266-9243.
Article Images
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PhotoCredit: Photo Credit: Matt Lavin
Image 1 Caption: Common Tansy
Photo Credit: Matt Lavin
