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Photo Credit: Steve Dewey, Utah State University, Bugwood.org -
Photo Credit: Jan Samanek, Phytosanitary Administration, Bugwood.org
Also known as: common tansy, golden-buttons, garden tansy
Originally brought to North America from Eurasia in the 1600s, common tansy has slowly spread westward. It is distasteful to livestock and displaces desirable forage plants in pastures.
Description:
| Life Cycle: | Perennial (life cycle lasts more than one year) |
| Early Detection and Rapid Response species: | No |
| Height: | Up to 5 feet (1.5 meters) |
| Leaf Description: | Fern-like leaves have narrow, toothed leaves. They become smaller towards the top of the stalk and produce a strong aroma when crushed. |
| Fruit & Flower Description: | Flowers are yellow and button-like and arranged in flat-topped clusters. It is a prolific seeder. Each plant produces around 2,500 seeds annually. Its seeds can be dispersed by wind, water, and equipment. |
| Bloom Time: | July to August |
Habitat:
- It is found along roadsides, streambanks, and in pastures.
- It is extremely hardy and grows in a variety of soil types and light conditions.
Impact:
- Tansy stands are dense and outcompete native plants, crops, and forage for livestock.
- It is reportedly poisonous to livestock, though it is seldom grazed due to its strong odor.
What you can do about it:
- Prevention is the best control – make sure to remove all seeds from personal gear, equipment, and animals before leaving an infested area.
- Mowing before the plant produces flowers and seeds is beneficial. Repeated mowing is required to keep plants from re-sprouting.
- Small infestations can be hand pulled or dug up. This is easiest and most effective in the spring after a rain when the ground is damp and before the plant has produced seeds.
Look-alikes:
Common tansy is often confused with a couple other invasive species: St. John’s wort (Hypericum perforatum) and tansy ragwort (Jacobaea vulgaris). Unlike tansy ragwort and St. Johns wort, common tansy’s flowers are button-like and do not have petals.
Noxious Weed Listing:
| State of Oregon: | Not listed |
| State of Washington: | Class B |
More Resources:
Download the Common Tansy Best Management Practices Factsheet
- Pacific Northwest Weed Management Handbook: Common tansy
- University of California, Weed Research & Information Center: Common tansy