Native to North America, and distributed from New Mexico north to Idaho, and east to Wisconsin and Ohio. Generally a plant of the north central states.
A biennial to short lived perennial, with reproduction from seeds. A common roadside weed in the Rocky Mountain states, but not so invasive as to pose a threat to pasturelands.
Mature plants grow to 6 feet in height, with a primary stalk and several branches from this. The leaves are very long and deeply lobed, each lobe a narrow extension with yellow spines at the tip of the lobe, and with short spines lining the entire leaf margin. All plant parts are covered with fine white hairs, giving the plant an overall grayish color. The large white flower heads grow from the ends of the stems, sometimes grouped in small clusters of 2 or 3 flower heads. The bulbous bract below the flowers also is covered with short spines.
Characteristicts Important to Control:
Physical removal prior to seed maturation can effectively eliminate the weed. A pre-emergent herbicide may be necessary in areas where seeds have been deposited, and new plantings are planned.