Common mullein flowers are sulfur-yellow on terminal spikes that reach 20 inches in length.Common mullein is a biennial that produces a large, thick rosette of fuzzy leaves the first year and a single, stout, erect stem, 2 to 6 feet tall, the second year. The leaves are alternate, overlapping one another, light green, and densely woolly. Flowers are arranged in long terminal spikes and are sulfur yellow. Flowering and seed production occurs from June to August.

This weed was introduced from Europe, but is a native of Asia and is common throughout the temperate areas of North America. It is found along river bottoms, pastures, meadows, fence rows and disturbed areas. It is especially prevalent on gravelly soils.

Common mullein is a List C species on the Colorado Noxious Weed list.