Tansy ragwort

(Senecio jacobaea)
Not Known To Occur In Colorado

Tansy ragwort is a non-indigenous, poisonous weed native to Europe and Asia Minor, that is responsible for the deaths of thousands of livestock. It is a tap-rooted biennial or short-lived perennial reaching 1 to 6 feet in height. The stems are stout and erect, with slightly branching characteristics. The leaves are 2 to 8 inches long, alternate and equally distributed mostly pinnately lobed, with the terminal lobe generally larger than the lateral ones. When the leaves are crushed, they give off a rank odor. The flowers form in clusters at the end of erect branches. The flowering heads are numerous and contain ray and disk flowers that are yellow in color. The flowers have 10 to 13 petals and are 1/4 to 1/2 inch long. The stems may be solitary or multiple up to the inflorescence. The seeds are pappus and are carried by the wind, each plant can produce up to 150,000 seeds.

Tansy ragwort fact sheet