Ask yourself whether you want to care for common mullein flowers or work desperately to keep them under control. Each plant can produce more than 100,000 seeds and grow to a height of 10 feet in ideal conditions, according to the website of Fairfax County, Virginia, public schools. If you want a towering weed, this is the one. This biennial plant gradually produces yellow flowers along its towering stalk, shedding seeds in late summer that can last up to 100 years, waiting for the right conditions for germination.
Choose a planting site that gets full sun for most of the day. Cultivate a square yard of soil to a depth of 4 inches, breaking up clods and clumps with a spade and removing old vegetation.
Scatter mullein seed over the soil, then cover the seed with 1/2 inch of additional soil. Moisten with water. Seeds will germinate within two weeks. Thin them back, leaving two or three of the healthiest seedlings.
Water occasionally in the first growing season. Mullein is a very hardy weed and will need little care. In the first year, the plant will reach a height of only 5 inches, with fuzzy, bluish-green leaves in a rosette pattern. Cover them with leaf litter in the fall to insulate them against cold.
Resume occasional watering in the spring. Expect more rapid growth in the second growing season, producing a tall flower stalk with yellow blossoms resembling hollyhock.
Cut back flower stalks with small pruning shears when flowers fade. This will help control the wild spread of mullein, which grows only from seeds. Volunteer seedlings that escape may be easily pulled, now that you know what the first-year plants look like.
Mullein roots are shallow and may be pulled easily.
Common mullein is a considered a medicinal plant, traditionally for coughs and lung disorders.
Common mullein is easiest to control when small. Second-year plants produce more than 100,000 seeds.