Common Tansy
Tanacetum vulgare
Washington State Classification
Class B — Control Required (Designated)
Common tansy is reported to be poisonous to livestock, though it is seldom grazed due to its strong odor.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
Common tansy is an aromatic perennial with rhizomes, reaching 1 to 5 feet tall, with fern like foliage and yellow button-like flowers.
Leaves
Leaves are alternate and pinnately compound (leaflets arranged on both sides of a common stalk). They are deeply divided into numerous, narrow, toothed segments. Leaves become smaller towards the top of the stalk and are strongly aromatic when crushed.
Flowers
Flowerheads are numerous, button-like and yellow. They are 1/4 to 1/2 inches across in flat-topped dense clusters. Flowerheads composed of all disk flowers and are absent of ray flowers.
Fruit & Seeds
Seeds are small (1 to 2 mm), gland dotted and with ribs. Seeds have crown shaped pappus.
Impact
Common tansy is reported to be poisonous to livestock, though it is seldom grazed due to its strong odor. It displaces forage plants, reduces wildlife habitat and species diversity.
Ecology & Spread
Habitat
Common tansy is generally found along roadsides, waste areas, streambanks and in pastures. Please click here to see a county level distribution map of common tansy in Washington.
Spread Mechanisms
Reproduction
Common tansy reproduces by numerous tufted seeds dispersed by wind and water. It also reproduces vegetatively by forming new plants from root fragments.
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