Mullein is a general name for a large genus of flowering plants called Verbascum; the most commonly used species from this genus being Verbascum thapsus. For thousands of years, the leaves of these plants have been used for herbal medicine, and certain parts of the plant are still used today. Commonly found in the United States, as well as areas of Europe and Asia, this herb is safe to use internally in medicinal quantities, although there are some side effects. In many areas, the hardiness of this plant has made it an invasive species, particularly in agricultural farmland. 
There are many impressive benefits to using mullein leaves, particularly for respiratory ailments, cardiovascular health, and various infections, among others.
Bursitis: Using the leaves or flowers topically on the knees to calm bursitis
Ear infection: Crushing mullein leaves into a paste to alleviate ear infections [3]
Disinfectant: Brewing the leaves into a tea or tincture can be used as a disinfectant
Respiratory health: Soothing respiratory ailments, such as asthma, sore throat, and dry cough
Chest infections: Speeding up recovery from bronchitis and chest infections
Wounds: Antiseptic, antiviral, and antibacterial agent for topical inflammation and wounds [4]
Hair care: Stimulating hair growth and protect against dry scalp
Inflammation: Soothing inflammation from gout and migraines
Heart health: Aiding in heart health by reducing inflammation of blood vessels
Stomach upset: Treating stomach upset, constipation, and diarrhea
Mullein Uses
As mentioned, there are many uses for mullein, and it is not only the leaves but also the seeds and flowers that can aid in your herbal healing.
You can brew the dried leaves into a tea
You can extract the essential oil from these leaves
You can mix crushed leaves into a smoking blend
The leaves and flowers can be made into a tincture
You can crush the seeds and mix them with water to form an anti-inflammatory paste
While this plant has been used for thousands of years, there is still a dearth of modern research on the many effects, but the anecdotal evidence is overwhelming.