Common tansy (Tanacetum vulgare L.), also known as garden tansy and golden buttons, is a perennial forb that reproduces by seed and rhizomes. It was first introduced to the United States from Europe in the 1600s. Cultivation for traditional folk medicines and ornamental plantings accelerated its spread throughout temperate regions of North America (Figure 1). Common tansy is currently listed as noxious in four western states and Minnesota.
Common tansy is an aggressive plant that can form dense vegetative colonies, especially on disturbed lands. The plant often occurs in association with other noxious weeds including knapweeds (Centaurea sp.) and Canada thistle (Cirsium arvense). Sites most susceptible to invasion include roadsides, fence rows, pastures, vacant lands, irrigation ditches, stream banks, and waste areas.
Common tansy displaces desirable grasses and forbs, impacting livestock grazing and wildlife habitat. The plant also contains alkaloids that can be toxic to both humans and livestock if consumed in large quantities. However, volatile oils produced in the leaves and flowers deter grazing by cattle and horses.
Identification and Spread
Mature common tansy plants are easy to recognize by the flat-topped clusters of small, button-like, yellow flowers that lack ray petals (Figure 2). Plants are herbaceous and 3 to 5 feet tall with erect stems. Leaves are alternate and pinnately compound (leaflets arranged on both sides of a common stalk) and irregularly lobed with leaves becoming smaller towards the tip of the stalk. Leaves and stems are strongly aromatic when crushed.
Common tansy reproduces by seeds and rhizomes. Flower heads remain intact and can hold seeds through the fall until they are physically dislodged from dried flower heads. Seeds are spread by both wind and water. Established plants also spread by brown, creeping rhizomes forming dense patches.
Management with Herbicides
Field trials were established at two locations in western Montana to determine effectiveness of various herbicide treatments on common tansy (Duncan et al. 2011). Sites included either common tansy alone or growing in a complex with spotted knapweed (Centaurea stoebe). Herbicide treatments included Milestone® herbicide at 5 and 7 fluid ounces of product per acre (fl oz/A), Opensight® herbicide at 1.5, 2.5 and 3.3 ounces of product per acre (oz/A) and metsulfuron at 0.5 oz/A applied at bloom growth stage. Plots were visually evaluated for percent control 12 and 27 months after treatment (MAT).
Results from the field studies indicate that Opensight at all rates applied provided greater than 95 percent common tansy control 12 MAT. This high level of control was maintained for 27 MAT with Opensight rates greater than 2.5 oz/A. Milestone did not provide acceptable control of common tansy. Although Opensight and metsulfuron provided similar control of common tansy, Opensight provided more than 95 percent control of both common tansy and spotted knapweed. Conclusions from the study indicate that on sites having a complex of weeds such as common tansy, knapweeds, and thistle, Opensight herbicide at rates of 2.5 to 3.3 oz/A provide excellent control of the weed complex compared to either metsulfuron or Milestone herbicide alone.
Other Management Methods
Hand digging can control small newly established infestations of common tansy. Rhizomes must be completely removed to effectively control the plant.
Common tansy is normally controlled in cultivated cropping systems. Tillage alone or in combination with herbicide application must be conducted periodically since common tansy can regenerate from rhizomes and seed.
Mowing, if applied pre-bloom, will reduce flowering and seed production. Mowing height should be a minimum of four-inch stubble height to maintain vigor of desirable plant species, which may replace common tansy over time with repeated mowing. Mowing after flowering and seed set may increase the spread of common tansy seeds.
Common tansy is reported to be toxic to livestock, and abortions in cattle were reported from the midwestern United States. However, most classes of livestock and some wildlife have been observed to eat common tansy with no known adverse effects. Sheep have been used to manage common tansy in Montana. Long-term impacts of repeated sheep grazing on common tansy population size and plant community dynamics are not known, but observations suggest common tansy populations may be decreased and grass populations increased with consecutive years of season-long sheep grazing (Jacobs 2008).
Applying cultural practices that strengthen the competitiveness of the plant community, such as prescribed grazing and forage harvest management will help prevent establishment of common tansy. Treatment of small satellite populations before plants become well established and spread should be a high management priority. Re-vegetation with desirable competitive plants will improve the longevity of common tansy control practices on disturbed sites.
Duncan CA, J Marks, and M Halstvedt. 2011. Common tansy control in riparian areas. In: Proceedings, Western Society of Weed Science (64) ISSN: 0091-4487. p. 59.
Jacobs J. 2008. Ecology and management of common tansy. USDA, NRCS, Invasive Species Technical Note No. MT-18. [Online] http://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/mtpmstn7819.pdf.
LeCain R and R Sheley. 2006. Common tansy (Tanacetum vulgare). Montana State University Extension MontGuide. MT 199911 AG. 4 p.
Mitch LW. 1992. Intriguing world of weeds – tansy. Weed Technology 6:242-244.
USDA, NRCS. 2019. The PLANTS Database (http://plants.usda.gov, 20 April 2019). National Plant Data Team, Greensboro, NC 27401-4901 USA.
Published Sept. 1, 2014; Revised April 2019
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Milestone and Opensight herbicides are 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. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas, or rotating the treated area to sensitive crops. Consult the label before purchase or use for full details. Always read and follow label directions.