Scientific name: Tanacetum vulgare

 

Identification and Impacts

Common tansy (Tanacetum vulgare L.) is a perennial plant that reproduces by both seed and creeping rootstocks. Seeds are yellowish brown achenes with short, five-toothed crowns. Yellow flowers are numerous in flat-topped dense clusters at the tops of the plants. Button-like flower heads lack ray flowers. Flowering typically occurs from July to September. The leaves are alternate, deeply divided into numerous narrow, individual leaflets. Mature plants are 1.5 to 6 feet tall. Stems are often purplish-red in color and extensively branched towards the top. The foliage emits a strong odor when crushed.

Habitats for Common tansy include along roadsides, streams, irrigation ditch banks, waste places, ornamental beds and in pastures. It grows best in full sun and on fertile, well-drained soil. Common tansy is found throughout the United States, although it is native to Europe.

Common tansy is considered undesirable forage for livestock. The plant is considered toxic if large quantities are consumed; fortunately animals rarely ingest it as it is very unpalatable. Common tansy can impact forage quality and quantity. With adequate moisture common tansy will displace native and other desirable species.\

The key to effective control of Common tansy is to stop the establishment and spread of infestations. Mechanical and hand cutting/pulling can assist with limiting seed production, but will not eradicate plants. Common tansy is considered toxic, use protective equipment when controlling. Another effective contol method is using herbicides. A combination of these two methods, will offer desirable results. Since Common tansy grows rhizometously, depleting the storage of carbohydrates in the root system will help control the plants. Details on the back of this sheet can help to create a management plan compatible with your site ecology.

Common tansy is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be either eradicated, contained, or suppressed depending on the local infestations. For more information visit www.colorado.gov/ag/weeds and click on the Noxious Weed Management Program or call Douglas County Weed Management at 303.660.7480.

Integrated Weed Management Recommendations

Cultural - Prevent the establishment of new infestations by minimizing disturbance and seed dispersal, eliminating seed production and maintaining healthy native communities. Contact your local Natural Resources Conservation Service for seed mix recommendations. Maintain healthy pastures and prevent bare spots caused by overgrazing.

Biological - There is no biological control available for Common tansy. Since biological control agents take years to research, develop and release, no releases are expected in the foreseeable future. For more information, contact the Palisade Insectary of the Colorado Department of Agriculture at 970.464.7916.

Mechanical - Controls such as hand cutting are most effective in combination with other methods. Tansy regenerates from root fragments, so cultivation could expand the size of an infestation. Common tansy can be mowed just before flowering and seed set to decrease seed production. This method may have to be repeated to eliminate re-growth from the rootstocks.

HERBICIDES

NOTE: The following are recommendations for herbicides that can be applied to range and pasturelands. Rates are approximate and based on equipment with an output of 30 gal/acre. Please read label for exact rates. Always read, understand, and follow the label directions. The herbicide label is the LAW!

HERBICIDE	RATE	APPLICATION TIMING
Metsulfuron (Escort XP)	1 oz product/ac. + 0.25% v/v non-ionic surfactant	Apply to when in bolting to bud growth stages. (Late Spring to Mid Summer)