They are biennial or perennial plants, rarely annuals or subshrubs, growing to 0.5–3 m tall. The plants first form a dense rosette of leaves at ground level, subsequently sending up a tall flowering stem. Biennial plants form the rosette the first year and the stem the following season. The leaves are spirally arranged, often densely hairy, though glabrous (hairless) in some species. The flowers have five symmetrical petals; petal colours in different species include yellow (most common), orange, red-brown, purple, blue, or white. The fruit is a capsule containing numerous minute seeds.

The plant has a long history of use as a herbal remedy,^[3] and is an effective treatment for asthma and respiratory disorders.^{[dubious – discuss]} Extracts made from the plant's flowers are a very effective treatment for ear infections.^{[citation needed]} Although this plant is a recent arrival to North America, Native Americans used the ground seeds of this plant as a paralytic fish poison due to their high levels of rotenone.^{[citation needed]} One species, Verbascum thapsus (Great mullein), is used as a herbal remedy for sore throat, cough, and lung diseases.^{[citation needed]}

In gardening and landscaping, the mulleins are valued for their tall narrow stature and for flowering over a long period of time, even in dry soils. Since the year 2000, a number of new hybrid cultivars have come out that have increased flower size, shorter heights, and a tendency to be longer-lived plants. A number have new colors for this genus. Many mulleins are raised from seed, including both the short-lived perennial and biennial types.

Mullein is the active ingredient in many alternative smoking blends.

It is considered a first-rate drill for use in the hand drill method of friction fire lighting