Mullein grows both as a weed and as a cultivated plant in herb gardens. The large, slightly furry leaves are preserved for use in herbal teas. Mullein plants reach between 1 and 8 feet in height, with leaves sized to match their stature. According to the Kansas State University Research and Extension service, mullein tea is beneficial for treating mild sore throats and has antiseptic qualities. The leaves must be harvested and dried properly, otherwise they will mold or mildew during storage.
Pick leaves from the top and middle of the mullein plant, as bottom leaves are often dirty or infested with insects. Choose healthy leaves that have no signs of damage.
Spread the mullein leaves out on a drying screen. Use a clean window screen if you don't have a permanent drying screen. Place the leaves on the screen so they do not touch or overlap.
Set the screen in a room that is not in direct sunlight. Open a window or turn on a fan to provide air flow around the leaves and speed up the drying process.
Dry the leaves for three days. Turn over each leaf and dry them for an additional three days.
Check for spots that aren't completely dry yet on the leaves. If some leaves aren't quite dry yet, continue drying them for two to three more days. Store the dried leaves in an airtight bag or container until they are ready to use.