This aromatic perennial has many tall stems, 2 to 4 ft tall. The leaves are similar to rose leaves, with each dark green leaflet being narrowly toothed. Numerous glands on the leaflets emit a strong, rank odor when crushed.

The slightly ridged stems are topped by numerous gold button-like flowers, each approximately 1/4 inch in diameter. Between 20-200 flowers make up the flat topped cluster. Tansy is often confused with tansy ragwort (Senecio jacobaea), which has ray flowers. Tansy reproduces from seeds and (to a limited extent) rhizomes.

Tansy is prevalent along fence lines. Since it was, and still is to some extent, a garden plant, it is commonly spotted in abandoned farm yards, hedgerows, fencelines, waste ground and roadsides.

In overgrazed range and permanent pasture, it will behave as an increaser i.e. increase in size and number to take the place of grasses removed by overgrazing. It can lead to abortions or death if livestock eat it due to a shortage of suitable plants. Control: Grazon*.


Source:
"Problem Weeds - A Cattlemen's Guide", Saskatchewan Agriculture and Food