The great mullein (Verbascus Thapsus), also called a common mullein, is part of the Figwort family of plants. Native to Europe but naturalized in many parts of the United States, the great mullein is sometimes invasive. The plant produces so many seeds that it can take over an area, shading out more desirable native species. The Plant Conservation Alliance, Alien Plant Working Group website describes the great mullein as a monocarpic perennial, meaning the plant requires two or more years to bloom and then perish.
Developing from its seeds in the first year of its existence, great mullein takes the form of a rosette of leaves approximately one to two feet across. One of the plant's strengths is its deep taproot, which helps it garner moisture in dry weather. The mullein shoots up dramatically during its second year, growing sometimes to a height of seven feet under perfect conditions. The great mullein typically lacks any branches and has a hairy, woolly stem. The leaves grow alternately on the stem and those lower down on the plant may be a foot long, with the leaves higher up much smaller. The leaves have a whitish to grayish-green tint, due to the colors of the minute hairs on their surfaces.
The stem of the great mullein features a thick spike of flowers at the top, with the flowers covering a length of from six inches to as much as two feet. The flowers are relatively small compared to the rest of the great mullein. Five yellow petals comprise a three-quarter of an inch wide flower that blooms during summer. The flowers will not all bloom in unison, instead taking turns blossoming during the warmer months. The flowers gradually change into a seed capsule containing the seeds of the great mullein. As the winter approaches, the leaves die but the main stem of the mullein remains, with the seedpods opening up and scattering a myriad of tiny seeds into the wind.
Few places in North America do not suit the growing habits of the great mullein. The plant grows across the entire continent with the exception of the Yukon and the Northwest Territories of Canada. You will find great mullein growing in waste places and in fields. Often you will encounter great mulleins growing in numbers on the side of the road. Vacant lots and the areas near railroad tracks are a great place to view this species.
As long as a region with a growing season no less than 140 days receives at least three to six inches of annual rainfall, the great mullein can grow there. The plant prefers sandy and dry soil, but has the ability to grow elsewhere. One thing the great mullein does require is sun, and plenty of it. The species will not grow in the shade. The seeds of the great mullein, according to the Illinois Wildflowers website, can lay in the ground dormant for decades and then suddenly germinate.
A laundry list of uses for the great mullein exists, with the "National Audubon Field Guide to Wildflowers" stating that the Romans would immerse the thick flower spikes in grease and create a usable torch from the plant. Early settlers and Native Americans alike would take the leaves and line their footwear with them for insulation from the cold. The leaves of great mullein, when brewed in a tea, helped fight colds. The flowers and the roots have medicinal applications, as well.