Common mullein is on the Colorado Noxious Weed List C and is found at elevations from 4,500 to 9,000 ft. on sunny, disturbed sites, including prairie dog colonies. It was first noted as a common weed in Boulder in 1905. It is a biennial. Rosettes of leaves covered with fine hairs are produced in the first year. The second year produces a single stout stem and wooly leaves and flowers. An adult mullein can produce 100,000 – 180,000 seeds. The seeds may last more than 80 years. List C plants are selected for control methods.
Colorado Weed Management Association definition of a noxious weed: "They are non-native plants that are disrupting our native vegetation and ecosystems. Noxious weeds threaten our drinking supply, agricultural crops, pasture lands and native habitats."
This plant is native to Asia but was introduced to the U.S. by early European settlers. Once the soil of an area is disturbed, the seed has been known to germinate, even after it has been buried for a long time.