Verbascum thapsus
Common mullein
Verbascum thapsus (Common mullein)
Mullein is native to Europe, Asia and northern Africa. Someone imported it into colonial America and it spread, By the early 19th century at least one botanist assumed it was native here. Today it's in every state, and the temperate part of Canada.
The plant needs a lot of sun and usually grows in open fields or disturbed areas.
Verbascum is biennial. The first year it just grows leaves. The second year it grows one stiff, erect stem with a spike of yellow flowers at the top. In Colorado it's usually a few feet tall, but it can get as tall as a person.
Verbascum flowers are small -- just a couple centimeters wide -- and radially symmetrical. They have five petals and five green sepals. The flowers in a spike don't bloom all at once. Some appear and are replaced by green seed capsules as other flowers start to bloom. The result is a green and yellow spike with flowers and capsules randomly along it.
The seed capsules dry out and and seeds drop to the ground. Each plant can produce more than a hundred thousand seeds. They don't all grow right away. Some can stay dormant in the soil for years -- possibly decades.
The plant starts to die near the end of summer, and eventually becomes a brown pole that can last through the winter.
Verbascum thapsus Common mullein
The tiny trichomes branch out like starlight, a shape called stellate (stell-at). This amazing picture of them was taken through a microscope with "Transmitted Circular Polarized Light Illumination." I don't know what that means, but it comes from a website that's full of great microscope images.
Why are the hairs shaped like that? It's because a gene mutation caused "cell divisions that are perpendicular to the main growth axis."
Verbascum glints silvery in sunlight and looks soft and velvety in dimmer light. It's because the whole plant is covered with fine hairs or, as a botanist would put it, "pubescent with trichomes."
Verbascum thapsus Common mullein
Mullein leaves are simple, oblong to ovate and grow alternately in a rosette. The lowest leaves are big (up to a foot long and 4 inches wide) and often lying on the ground. The leaves get smaller as they get higher, eventually disappearing to leave the bare stem.
The leaf margins are entire to slightly crenate and sometimes wavy. The lower ones have short petioles; the upper ones don't, but at the base they wrap around the stem.
In Europe, where it's native, people call it "great" mullein. It gets less respect as an invader here. We call it "common" mullein and sometimes cowboy toilet paper.
The genus name Verbascum is generally thought to come from the latin word "berbascum" which means "plant with a beard." But there are other theories.
Thapis comes from the Greek and Latin words for a poisonous shrub.
Ancient Romans supposedly stuck dipped the dried spikes in oil and used mullein plants as torches. I've got to test that someday.
