Verbascum thapsus is an erect herb in the family Scrophulariaceae. It is found in neglected meadows and pasture lands, along fencerows and roadsides. It can produce 100,000-180,000 seeds per individual plant and seeds may remain viable for over 100 years. Verbascum thapsus threatens natural meadows and forest openings, where it adapts easily to a wide variety of site conditions and an established population can be extremely difficult to eradicate. Verbascum thapsus was once used as a herbal remedy for bronchitis, colds and congestion.
Verbascum thapsus is described as an erect herb. During the first year V. thapsus are low-growing rosettes of bluish gray-green, with felt-like leaves that range from 10cm to 30cm in length and 2.5cm to 13cm in width. Mature flowering plants are produced the second year, and grow to 1.5 to 3.0 metres in height, including the conspicuous flowering stalk. The five-petaled yellow flowers are arranged in a leafy spike and bloom a few at a time from June-August. Leaves are alternate along the flowering stalks and are much larger toward the base of the plant. The tiny seeds are pitted and rough with wavy ridges and deep grooves and can germinate after lying dormant in the soil for several decades.
Agricultural areas, ruderal/disturbed.
Verbascum thapsus is found establishing in neglected meadows and pasture lands, along fence rows and roadsides, and in industrial areas throughout North America.
An important characteristic of Verbascum thapsus is its ability of adapting to a variety of site conditions. It grows more vigouously than native herbs and shrubs wherever it establishes. V. thapsus threatens natural meadows and forest openings. It is a prolific seed bearer with seeds remaining viable for long periods in the soil. An established population of V. thapsus can be extremely difficult to eradicate.
Remaley (1998) states that Verbascum thapsus, “Was first introduced into the U.S. in the mid-1700′s, where it was used as a piscicide, or fish poison, in Virginia. It quickly spread throughout the U.S. and is well established throughout the eastern states. Brought over from Europe by settlers, it was used as a medicinal herb, as a remedy for coughs and diarrhea and a respiratory stimulant for the lungs when smoked. A methanol extract from common mullein has been used as an insecticide for mosquito larvae.”
Native Range:Asia, and Europe.
Known Introduced Range: USA, Canada, Australia, New Zealand, Chiule, Argentina.”
Preventative measures: As Verbascum thapsus seedling emergence is dependent on the presence of bare ground, sowing sites with early successional native grasses or other plants may decrease seed germination and the chance of successful emergence of V. thapsus seedlings.
Manual: Hand pulling of seedlings should be undertaken after they are large enough to grasp but before they produce seeds, while hand hoeing can destroy very small plants by exposing their root systems to the sun, causing them to desiccate. Small infestations of mullein can be removed by hand digging. Although this is a slow and laborious technique it is suitable for sensitive areas, such as around other desirable trees or shrubs, where other methods may not be suitable.
Mechanical: Scarification, the use of ploughs and discs to uproot plants, is not recommended for the control of mullein. This is because it creates areas of bare ground that are ideal for the establishment of new mullein populations. Regular cultivation is known to be adequate for the control of mullein. Tractor-mounted mowers or scythes can be used to trim mullein, depending on the terrain. The best time to cut is when the plants begin to flower. Repeated mowing will prevent the flower stalk from bolting but if mowing is then discontinued then the plant will bolt and produce flowers.
Biological: Intentional establishment of late successional native plants among mullein infestations may result in the weeds being outcompeted and thereby eliminated.