General: Tall aromatic plant with clusters of yellow flowers.
Height: Grows to 1.5m.
Flowers: Flowers are yellow button-shaped with no petals. The form dense, flat-topped clusters at the top of the plant.
Leaves/Stems: Leaves are a fern-like shape , are dark green and serrated. Stems are often purple to red in colour and dotted. When crushed the leaves and stems have strong odour.
Root: Creeping root system. Often short, thick and many lateral roots.
Tansy Ragwort (Senecio jacobaea), another invasive plant.
Differences: The key difference is the flowers. Tansy ragwort has petals and Common tansy does not.
Where did it come from? Originally from Europe and introduced as a garden ornamental and a medicinal herb.
Where does it grow here? Scattered at low to mid-elevations especially disturbed sites like roadsides, gravel pits, and pastures. It prefers full sun and well-drained soils. It is more abundant in the areas of the region that receive more moisture like the highway corridor between Lillooet and Pemberton.
Reproduction: It grows by seed and root.
When does it grow, flower & seed? Sprouts April-May. Flowers June-August. Seeds September-October.
Spreads By: Highway activities like mowing and grading does spread this plant to new locations. Spreading of seed infested gravel onto highways also establishes new locations. People do plant this in their gardens.
Plant Type: Perennial.
Southern Interior Weed Management Committee. 2016. Invasive Plants of the Southern Interior BC. 86pgs.
Okanagan Invasive Species Online website