Common tansy (Tanacetum vulgare)

A cluster of round, yellow tansy flowers.

 
 
Common tansy is a perennial plant with distinctive yellow button-like flowers. It can form dense cover and degrade pastures, impede reforestation efforts, and outcompete native plants.

Warning: Eating common tansy can be toxic to humans and livestock. Wear gloves when handling common tansy.

Description

Appearance

Common tansy is a perennial herbaceous plant that can grow 3 - 5 feet tall. A single stem branches extensively toward the top into short stems forming a flat-topped cluster of numerous yellow, button-like flower heads.

Leaves and stem

Common tansy leaves come off the stem in an alternating pattern. The leaves themselves are deeply divided, irregularly lobed, have serrated edges and have leaflets arranged on both sides of a common stalk (pinnately compound). Leaves become smaller towards the top of the stalk, and are strongly aromatic when crushed.

Flowers

Flowers are bright yellow discs up to a half an inch wide. The flowers look somewhat like daisies that are missing their white petals and bloom from July through October.

Seeds

Each plant produces numerous small, brown, tufted seeds that are dispersed by wind, water, and human activities such as mowing.

Rhizomes and roots

Common tansy spreads vegetatively by underground stems that send out roots and shoots (rhizomes) and it can form new plants from small root fragments.

Biology

Common tansy is a perennial plant. It reproduces by seed and can also spread by rhizomes and root fragments. It is most often found in dry soils growing in full sun. Often, it is found in open, disturbed areas such as roadsides, gravel pits, and pastures. It was also planted in gardens so can be found near old homesteads.

Origin and spread

Common tansy was introduced to the United States from Europe for medicinal purposes. Seeds have spread from places where common tansy was planted intentionally.

Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

  • Stiff goldenrod, Solidago rigida (native) – Stiff goldenrod flowers have yellow petals around a yellow center while tansy flowers do not have that type of petals. Stiff goldenrod leaves are oval and smooth while common tansy leaves are deeply lobed and serrated.
  • Oxeye daisy, Leucanthemum vulgare (invasive) – Oxeye daisy flowers have white petals around a yellow center while tansy do not have that type of petals.
  • Garden valerian, Valeriana officinalis (non-native) – The leaves of garden valerian can look similar to common tansy but garden valerian leaves are not toothed and the flowers are white.
 
Regulatory classification
Common tansy is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Control List meaning that efforts must be made to prevent the spread of seeds or other propagating parts. Additionally no transportation, propagation, or sale is allowed.

Threat to Minnesota
  • Common tansy forms dense cover that can outcompete native plants.
  • It can be toxic to cattle and horses. It can become abundant in pastures and reduce available forage.
  • Dense common tansy can make it difficult for trees to establish so it can negatively impact timber production and habitat restoration.
What you should do
One way that invasive plant seeds and fragments can spread is in soil.  Sometimes plants are planted purposefully.  You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals and mud from boots, gear, pets and vehicles.
  • CLEAN your gear before entering and leaving the recreation site.
  • STAY on designated roads and trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods
Mechanical control can be done by digging or pulling the plant by hand or with equipment such as a shovel. Root fragments left behind in the ground could resprout. Cover skin and wear gloves when handling common tansy. Mowing will not kill the plants but can reduce seed production. Mow from May to July to prevent flowering. Do not mow if plants have seeds (July and later), as this will spread the seeds.

Herbicide control can be done using systemic herbicides, which are taken up by plants and move within the plant, killing leaves, stems, and roots. Herbicides that can be effective for common tansy include glyphosate, 2,4-D, metsulfuron-methyl, and imazapyr. The herbicides should be applied as foliar (leaf) applications in the spring. Always follow the herbicide label instructions.

Biological control is under exploration. Insects from common tansy's native range are being studied to determine if any are appropriate for use as biological control insects in the United States. Biological control insects have not been approved for use at this time. The CABI common tansy biological control research webpage explains the project.

Reporting
Report new occurrences by submitting a report through EDDMapS, emailing Report a Pest, calling Report a Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources

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