See label for specific rates and timing of application. It is also recommended to use a surfactant and penetrator when applying these herbicides. The above picture shows common mullein in the second season's growth stage. Seeds are produced from the yellow flower. Below is common mullein in the first year of growth, the rosette stage.
Leaves are thick and woolly and therefore unplalatable to livestock.
The texture of the leaves also makes herbicide penetration difficult. Mullein Control Mechanical control such as mowing or handpulling can be effective is completed before seed production. The early bud stage, which would be before yellow flowers appear, is recommended. Common mullein does not produce seeds simultaneously, therefore you will see stalks that have seeds, flowers, and buds. The relevance of this is to mow, pull, or cut the stalk earlier in the summer because some flowers will produce seeds early in the season.