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Common Tansy

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Common Tansy Common Tansy

  • Why should we care?
    • Consumption or improper handling of this plant can result in illness, convulsions, and even death! The leaves and stems contain tanacetum, an oil toxic to humans and animals. This plant also threatens ecological health, as well as the economic value, of pastures, riparian areas and cropland through the reduction of livestock forage, species diversity and irrigation water. 
  • How to Identify
    • This invasive weed is found in sandy soils of open or disturbed areas (i.e., roadsides). It also appears in pastures, prairies, shorelines, hedgerows, and gardens. This invasive weed grows 2 to 5 feet tall, blooming from July through October. The stems are erect, reddish/purplish brown in color and un-branched except for the flowering portion. This plant has an alternate leaf arrangement with pinnately compound leaves and deeply serrate margins. The flowers are yellow, button-shaped disc flowers arranged in clusters at the top of stems. Each disc is composed of many small flowers and is strongly aromatic, especially when crushed. 
  • About the Plant and Where it came from
    • Tanacetum vulgare
    • Common Tansy is a member of the Asteraceae family or Composite family. This invasive weed is a perennial plant native to Europe that was introduced as a medicinal plant but has escaped cultivation to become a great threat to our native plant communities.
    • Common Tansy reproduces by seed, but can also spread by rhizomes (roots), which aids in the persistence of this invasive weed. This plant produces many seeds that are dispersed by wind and water. 
  • How to Control
    • Cultural control: Includes mowing and hand pulling before flowering to reduce seed production. Mowing after flowering will spread seed. When hand pulling wear gloves to avoid absorbing toxins through skin. Though Common Tansy is avoided by most livestock and is toxic if consumed in excess amounts, sheep and goats are known to graze on it and be an effective control method. Other livestock will trample it while grazing on other plants to out compete tansy at the expense of more sought-after plants. Tiling is also not effective because it leaves root fragments that will re-sprout.
    • Chemical control: Entails spot spraying 2, 4-D, clopyralid (Transline and Pyramid), or metsulfuron-methyl (Ally, Allie, Gropper, and Escort) with a surfactant. These chemical treatments are effective, but may need to be repeated. When applying chemical treatments to Common Tansy near water, use glyphosate (Round-Up) with a wipe on application. This is fairly effective, but may take 2 years to get significant results. Be sure to use the formulation approved for use near water.
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