Identification and Reproduction

Identification: 

• Common tansy is a perennial in the daisy family (Asteraceae).
• It grows upright from purplish-red stems.
• Leaves are alternate, deeply divided, toothed and dark green.

• Flowers are bright yellow with flat tops, appearing like buttons. Flowers form in clusters of 20-30 on each plant stalk. 

Reproduction:

• Common tansy is a prolific seed producer. Seeds can be spread by birds, animals, and people.
• It can also spread through rhizomes.

Habitat & Ecology

• Common tansy is present throughout southern B.C. and the Fraser Valley. 
• It can grow in disturbed sites and likes sunny, well-drained areas.
• Often found on pastures and roadsides.

Impacts

Social: 

• Plants contain a toxic alkaloid that is toxic to both humans and livestock. 
• Common tansy if consumed by dairy cattle has been found to produce an unpleasant milk. 

Ecological:

Dense patches of common tansy will displace native vegetation. 

Management

Mechanical/Manual Control:

• Mowing has the potential to reduce seed production, but will require repetition. It is most successful before flowering in July. 
• Hand cutting the seed heads is also effective. 
• In small patches hand pulling may be appropriate. 
• Be sure to wear gloves and other protective clothing to prevent skin irritation. 

For alternative planting options to common tansy, check out the ISCBC's Grow Me Instead guide.

Resources

Download A Guide to Weeds in British Columbia for Common Tansy here.

Header photo (Strecosa). 

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