Mullein (Verbascum thapus) is another of the many plants that were brought to North America from Europe by our ancestors seeking a better life in the New World. Mullein commonly was planted in gardens and on homesteads for its medicinal properties and, as with many plants, escaped its confines of cultivation. Ultimately, it has spread throughout all of continental United States and Canada.
As with many of the plants that civilizations adopt into their cultures, mullein is known by several names. These names commonly reflect some characteristic that the plant exhibits, such as the flower stalk or leaf texture. Common names for mullein include Aaron's rod, miner's candle, Shepard's club, St. Peter's staff, Jupiter's staff, beggars blanket, Adam's flannel, old man's flannel, velvet dock, wooly mullein, and many, many more. The number of names associated with this plant shows just how widely this plant was adopted into everyday life.
Plants that escape the confines of production and begin to grow and proliferate in areas where they are not wanted become known as weeds. Not often classified as a problem weed in our area, mullein is a weed, none-the-less. It can be found in a wide variety of environments, but prefers disturbed areas such as railroad rights-of-way, roadsides, fence rows, ditches, and pastures. It is one of the first weeds to germinate when an area is disturbed. It thrives in sunny, hot, dry conditions. When mullein germinates, it grows very quickly-much more so than the native plants that are trying to compete with it-and quickly gains a foothold.
Mullein is a biennial plant, meaning that the seed germinates and grows the first year, overwinters, produces seed the second year, and dies. The first year after the seed germinates, it develops into rosette of leaves 4-12 inches long and up to 5 inches wide that grows very close to the ground. The leaves are covered by dense hairs similar to felt that makes it very undesirable to livestock and wildlife that might feed on the foliage of the plant. The plant is supported by a shallow taproot system.
The rosette overwinters, and the second year a tall flower stalk up to 4 to 5 feet develops. The leaves expand and develop upward along the stalk as do the flowers. Yellow flowers begin developing on the lower portion of the stalk and expand upward as the plant matures. A single plant can produce 100,000 to 180,000 seeds. These can lie dormant and viable in the soil seed bank for as long as 100 years. The seed falls near the parent plant, depositing large amounts of seed for future generations. Mullein's huge seed production benefits a wide variety of wildlife including birds and mammals that feed on the seed. The plant itself and the flowers are habitat for a variety of non-pest insects and pollinators.
Mullein can be difficult to eradicate due to the great number of seeds that it produces, but there are a variety of control measures to reduce populations. One simple method is to ensure good competition through encouraging good groundcover. Mullein is a pioneer plant, one of the first to germinate in bare ground. For control, encourage good ground cover.
Manual and mechanical controls also can be very effective. The plant itself is very easy to pull because of its shallow taproot system. This is a great way to reduce seed dispersal, especially if pulled prior to the seed maturing.
In areas where manual control is not practical, chemical controls can be used. One-year old rosettes can be controlled easily using non-selective herbicides such as glyphosate (Round-up) products applied directly to the plant. Greater care must be taken when applying these products to the upright, two-year old plants to reduce drift to non-targets. Selective broadleaf herbicides such as triclopyr (Garlon) are a better choice in areas where desirable grasses may be present. It is important to use a surfactant or wetting agent in conjunction with the herbicide. The hairy nature of the leaf acts to repel water and the surfactant counters that action, allowing the herbicide to penetrate to the epidermis of the leaf.