Tanacetum vulgare (syns. Chrysanthemum vulgare, Tanacetum boreale)
Common tansy is an aromatic perennial with rhizomes, reaching 1 to 5 feet tall, with fern like foliage and yellow button-like 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. 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.
Height of mature plants
June through August
Common St. Johnswort (Hypericum perforatum) and tansy ragwort (Senecio jacobaea) may be mistaken for common tansy. Common St. Johnswort flowers have 5 petals per flower while common tansy does not have any petals (ray flowers) and and tansy ragwort has on average of 13 ‘petals’ (ray flowers).
The areas most infested by Weed X are important places that people care about. Weed X especially loves those particular places that are liked by all of these really cool native plants. So watch for Weed X is these really specific important places.
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.
Noxious Weed Listing:
- WeedWise: Maintenance
- State of Oregon: Not listed
- State of Washington: Class B
- Four County CWMA: Class C
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