Mullein (Verbascum thapsus), often called common mullein or great mullein, is a tall, distinctive biennial plant widespread across North America and Eurasia. Its unique appearance and two-year life cycle make it simple to identify visually. This guide focuses on the physical characteristics of the plant at each stage of its development. The plant’s life is divided into two distinct phases: a low-lying leaf structure followed by a towering flower spike.
Stage 1: The Rosette and Basal Leaves
The first year of Mullein’s life is spent entirely as a basal rosette, a circular arrangement of leaves that grows close to the ground. This formation can reach a diameter of two feet or more, spreading outward to absorb maximum sunlight. The leaves are large, typically oblong to oblanceolate in shape, and often measure between six and fifteen inches in length, creating a substantial ground cover.
The most defining feature of the rosette is its texture, which is uniformly covered in a dense layer of soft, star-shaped hairs called trichomes. This thick, woolly coating gives the leaves a flannel-like feel, leading to common names like “velvet plant” or “flannel leaf.” The dense hair covering also contributes to the plant’s distinctive pale grayish-green or silvery-green hue.
This woolly texture helps the plant conserve water and deter most grazing herbivores. The rosette stage is critical for storing the energy necessary to fuel the plant’s dramatic vertical growth in the following year.
Stage 2: The Flower Stalk and Bloom
In its second year, the Mullein plant sends up a single, rigid, vertical flowering stalk. This spike typically rises to a height of between five and seven feet, though some specimens can reach up to ten feet. The stalk is generally unbranched, adding to its prominent, pole-like appearance.
The stem remains densely covered in the same soft, woolly hairs found on the basal leaves. The leaves along the stalk are smaller and alternately arranged. These upper leaves are also decurrent, meaning their bases extend downward along the stalk, creating vertical ridges that give the stem a subtly winged appearance.
The bloom consists of a dense, cylindrical cluster of flowers, known as a raceme, occupying a significant portion of the stalk’s height. The individual flowers are small, measuring less than an inch across, and feature five distinct, bright yellow petals. Blooming occurs over an extended period from mid-summer into early fall, with flowers opening sequentially from the base of the spike upward.
Context: Where Mullein Thrives
Mullein is an adaptable plant that prefers environments where competition from other vegetation is minimal, making its habitat a strong clue for identification. It is most commonly encountered in disturbed areas, including roadsides, abandoned fields, clearings, and vacant lots.
The plant has a tolerance for poor soil conditions and thrives in dry, sandy, or rocky ground that other species might avoid. Mullein is notably intolerant of shade, which explains why it does not persist in densely wooded or established meadow areas.
Originally native to Europe and Asia, Mullein has naturalized throughout nearly all of the United States and southern Canada. Its success in these open, sun-exposed habitats is due, in part, to a persistent seed bank, where seeds can remain viable in the soil for decades.