The moth mullein is a biennial plant. In its first year after sowing, its leaves develop as a basal rosette. 
In the second year of growth, the stem grows slender and erect, and can reach a height of 1+1⁄2 to 3 feet (1⁄2 to 1 m). Sow in spring where they are to flower the following year. Seed saved by Blackthorne Trust.