The moth mullein is a biennial plant. In its first year of growth, the leaves of the mullein develop as a basal rosette. During this first year, the stem of the plant remains extremely short. The leaves of the rosette are oblanceolate with deeply-toothed edges and are attached to the stem by short petioles. The rosette can grow to a diameter of sixteen inches during this first year, with each individual leaf reaching a length of up to eight inches. The mullein forms a fibrous root system with a deep taproot. In the second year of growth, the stem of the mullein grows slender and erect, and can reach a height of 2 to 5 feet. This length of stem is commonly referred to as the flowering stem. It usually grows unbranched, and leaves grow alternatively directly off the stem. The flowers of the moth mullein are produced during the second year of growth, and are found in loose clusters near the top of the flowering stem. Each flower is attached individually to the flowering stem by a pedicel. Each pedicel typically reaches a length of less than one inch. The flowers of the mullein consist of five petals and five anther-bearing stamens, and each flower can reach a diameter of one inch. The flowers can be either yellow or white and typically have a slight purple tinge. The stamens of the flower are orange in color and are covered in purple hairs, reminiscent to a moth’s antennae.The flowers of the mullein bloom between June and October of the second year. The moth mullein grows a small, simple fruit that is spherical in shape and has a diameter of less than a half-inch. Each fruit is dark brown in color and contains numerous dark brown seeds. The fruit capsule splits in two and falls to the ground when mature.
Habitats include pastures, abandoned fields, vacant lots, irregularly mowed lawns, areas along roadsides and railroads, and gravel bars along rivers. It prefers highly disturbed areas and is not invasive of natural areas to any significant degree.