This plant, mullein its common name, can be seen throughout a vast portion of the Northern hemisphere including Europe, North Africa and Asia, from the Azores, the Canary Islands and the British Isles in the west to China in the east, and from Scandinavia and Siberia in the north to the Himalayas in the south. In addition, it has been introduced in Australia, New Zealand, tropical Asia, the Reunion island in the Indian Ocean, North America, Hawaii, Chile, Haiti and Argentina. It is found on roadsides, pasture lands and meadows.
In Europe, traditional lore made of mullein a lighting fixture: the shaft — about an inch (2.5 cm) in diameter — was stripped bare of leaves and covered with pitch. It could then be set aflame and serve as a torch in public events such as religious processions. It is indeed a tall plant growing to be 1-2 m (3.5-7 ft) tall.
The leaves are likewise big, up to 50 cm (1.8 ft) in length and 14 cm (6 in) in width. Flowers, blooming the whole summer from June to August, have five stamens attached to the petals, a five-lobed calyx tube and a bright yellow five-petalled corolla measuring 1.5 to 3 cm (0.8-1.2 in) in diameter. Any given flower remains open a single day, opening before dawn and closing in the afternoon. Seeds retain their germinating power for decades, up to a century reportedly.
All parts of the plant are covered by star-shaped hairs. It is a thick blanket on the leaves, making them look silvery and velvet-soft to the touch. The function of the hairs is to restrain water loss through evaporation. In past times, poor people roaming the European countryside would stuff these leaves into their wooden shoes to make them more comfortable.
Mullein employs both chemical and mechanical defenses against leaf herbivory insects and grazing animals. Two important chemical defense compounds are the iridoid glycosides aucubin and catalpol. These are monoterpene-derived compounds, present in more than 50 plant families, with demonstrated importance in shaping plant-insect interactions. The abundant hairs set up intense irritation in the mucus membrane of any grazing animal.
In folk medicine, mullein was used as a remedy for the respiratory tract, particularly in cases of irritating coughs with bronchial congestion. It was used also to treat asthma and against diarrhoea and migraine headaches.