Verbascum thapsus

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iVerbascum thapsus
Conservation status
Least concern (LR/lc)
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Lamiales Family: Scrophulariaceae Genus: Verbascum Species: V. thapsus
Binomial name
Verbascum thapsus L.

Verbascum thapsus (Great Mullein) is a species of mullein, native to Europe, northern Africa and Asia, from the Azores and Canary Islands east to western China, north to the British Isles, Scandinavia and Siberia, and south to the Himalaya^[1][2][3]. Other common names are Common Mullein, Woolly Mullein, Flannel Mullein, Shepherd's Club, and Aaron's Rod. The specific epithet thapsus was first used by Theophrastus for an unspecified herb from the Ancient Greek settlement of Thapsos, near modern Syracuse, Sicily^[4], though some have suggested it could be related to the ancient Tunisian city of Thapsus.^[5]

Contents 1 Morphology 1.1 Life cycle 2 Ecology 3 Cultivation and naturalisation 3.1 Agricultural impacts and control 4 Uses 4.1 Medical use 4.2 Other uses 5 Notes 6 References 7 External links

[edit] Morphology

It is a dicotyledonous biennial plant that produces only a rosette of leaves in the first year. In the second year it produces a tall stem 1-2 m tall (exceptionally to 3.5 m) with a dense spike of flowers on the upper half of the stem, only a few of which flower at the same time. All parts of the plant are covered with dense silvery star-shaped trichome hairs. The stem is solid, and is usually unbranched, rarely branched below the inflorescence, typically doing so when damaged; the dry stem and seed capsules usually persist in winter. The plants produces shallow taproots.^{[6][2][7][8][9]}

The leaves are alternate, thick and decurrent, varying between oblong and oblanceolate. The basal rosette leaves are the largest, up to 50 cm long and 14 cm broad, with steadily smaller leaves higher on the flowering stem.^{[6][10][8][11]}

The flowers are pentamerous, with a 5-lobed calyx tube and a yellow corolla 12-35 mm diameter, and five stamens. The flowers are almost sessile, with only very short pedicels (1-3 mm). The three upper stamens are longer, with their filaments covered with yellow or whitish hair, while the two other stamen have glabrous filaments. Flowering occurs throughout the summer. The fruit is an ovoid 3-10 mm long capsule containing large numbers of minute (less than a millimetre) brown seeds.^{[6][10][8][11]}

There are three subspecies:^[1]

• Verbascum thapsus subsp. thapsus. Widespread.
• Verbascum thapsus subsp. crassifolium (Lam.) Murb. Mediterranean region.
• Verbascum thapsus subsp. giganteum (Willk.) Nyman. Spain, endemic.

[edit] Life cycle

Common Mullein requires vernalisation before it can flowers, which is the reason why it is a biennial. Plants that germinate in autumn overwinter if they are large enough (rosette less than 15 cm across die in winter) before flowering the next year. The entire plant usually dies at the end of its second year, although some rare individuals remain vegetative a third year.^[11]

The individual flowers are open only for one day. They are autogamous and will self-pollinate if they have not been pollinated by insects during the day. While many insects visit the flowers, only some bees actually accomplish pollination.^[11][12][13] Visitors include halictid bees and hoverflies. Megachilid bees, notably Anthidium species, use the hair in making their nests. The seeds are generally too small for birds to feed on,^[14] although the American Goldfinch was reported to consume them.^[15]

The seeds maintain their germinative powers for decades, up to a hundred years, according to some studies.^[16] Because of this, and because the plant is an extremely prolific seed bearer (up to 180,000^[12][11] or 240,000^[13]), it can sprout from apparently bare ground^[11] or shortly after forest fires^[13] long after previous plants have died, and will likely be an initial colonist. Common Mullein rarely establishes on new grounds without human intervention because its seeds are not dispersed very far. Seed dispersion requires the stem to be moved by wind or animal movement; 75% of the seeds fall within a metre of the parent plant, and 93% fall within five metres.^[11]

[edit] Ecology

Common Mullein is most frequent as a coloniser of bare disturbed soil. This is in part due to its intolerance of shade and the very long periods that the seed can remain dormant before germination. It is not an agricultural weed, although its presence can be very difficult to completely eradicate, and is problematic in overgrazed pastures.^[11][12][13]

It favours dry, sandy or gravelly soils, although it can grow in a variety of habitats: meadows, roadsides, forest clearings and pastures. It germinates almost solely in bare soil, at temperatures between 10 °C and 40 °C.^[11] While it can germinate in total darkness if proper conditions are present (tests give a 35% germination rate under ideal conditions), in nature, it will only appear if the seeds are exposed, or very close to the soil surface. While it can also appear in areas where some vegetation exist, growth of the rosettes on bare soil is four to seven times more rapid.^[11]

[edit] Cultivation and naturalisation

It has been introduced throughout the temperate world, and is naturalised weed in, North America, Australia, Chile, Hispaniola and Argentina (1925).^[3][17][18] In the United States it was imported very early and cultivated for its medicinal properties. By the 1630s, it was already escaped and had begun spreading so much that Amos Eaton thought it was a native plant, and gives it as such in 1818.^[19] In 1839 it is already reported in Michigan and in 1876, in California.^[12] It is now found commonly in all the states,^[20] and all the Canadian provinces.

It is considered a noxious weed in Colorado (Class C),^[21] Hawaii^[22] and Victoria, Australia (regionally prohibited in the West Gippsland region, and regionally controlled in several others).^[23]

[edit] Agricultural impacts and control

Common Mullein is not considered an agricultural weed because it cannot compete with established plants, and is easily crowded out by them, except in areas where vegetation is sparse to begin with, such as Californian semi-desertic areas (Eastern Sierra Nevada), where it crowds out native herbs and grasses; its tendency to appear after forest fires also disturbs the normal ecological succession.^[11][13] Despite not being an agricultural weed itself, it hosts a number of insects and diseases, including both pests and beneficial insects.^[24] It is also a potential reservoir of the Cucumber mosaic virus.^[25] A study found V. thapsus to host insects from 29 different families of insect pasts. Most of the pests found were western flower thrips (Frankliniella occidentalis), Lygus species, such as the tarnished plant bug (L. lineolaris) and various spider mites from the family Tetranychidae. These make the plant a potential reservoir for overwintering pests.^[24] Other insects commonly found on Common Mullein are specific feeders such as mullein thrips (Haplothrips verbasci),^[24] Gymnaetron tetrum and the Mullein Moth (Cucullia verbasci).^[12] Useful insects are also hosted by Common Mullein, including predatory mites of the Galendromus, Typhlodromus and Amblyseius genera (Phytoseiidae), the minute pirate bug (Orius tristicolor)^[24] and the mullein plant bug (Campylomma verbasci).^[26]

Control of the plant, when desired, is best managed via mechanical means, including hand pulling and hoeing, preferably followed by sowing of native plants. Animals rarely graze it because of its irritating hairs, and herbicides require surfactants to be effective, as the hair causes water to roll off the plant, much like the lotus effect. Burning is ineffective, as it only creates new bare areas for seedlings to colonise.^[11][12][13] G. tetrum and C. verbasci usually have little effect on V. thapsus populations.^[12] Goats and chickens have been proposed to control Mullein.^[11] Effective (when used with a surfactant) contact herbicides include glyphosate,^[12][13] triclopyr^[12] and sulfurometuron-methyl.^[13] Ground herbicides, like tebuthiuron, are also effective, but recreate bare ground and require repeated application to prevent regrowth.^[11]

[edit] Uses

Great Mullein has been used since ancient times as a remedy for skin, throat and breathing ailments. It has long had a medicinal reputation, especially as an astringent and emollient. It contains mucilage, several saponins, coumarin and rotenone. Dioscorides recommended it for diseases of the lung. Non-medical uses have included dyeing and making torches.

[edit] Medical use

Dioscorides first recommended the plant 2000 years ago, against pulmonary diseases,^[27] and this has remained one of its primary uses, especially against cough. Leaf decoctions or herbal teas were used for expectoration, consumption, dry cough, bronchitis, sore throat and hemorrhoids. Leaves were also smoked against pulmonary ailments, a tradition that as transmitted rapidly to Native American peoples.^[28][29]

Oil from the flowers was used against catarrhs, colics and, in Germany, earaches, frostbite, eczema and other external problems. Topical application of various mullein-based preparation was recommended against warts,^[30] boils, carbuncles, and chilblains, amongst others.^[28][29] Recent studies have found Mullein (especially the flowers) to contain glycyrrhizin compounds with bactericide and potentially anti-tumoral action.^[31] In Germany, a governmental commission sanctionned medicinal use of the plant for catarrhs.^[32] It was also part of the National Formulary in the United States^[29] and United Kingdom.^[28] The plant's leaves, in addition to the seeds, have been reported as containing rotenone, although quantities are unknown.^[33]

In Spanish, Commmon Mullein is called Gordolobo, a name transferred on Gnaphalium conoideum, a plant with a similar appearance and uses by the Mexican Aztecs, and the two are both sold under the name "Gordolobo," which has lead to at least one case of poisoning due to confusion with Senecio longilobus.^[34]

[edit] Other uses

Like many ancient plants (Pliny the Elder describes it in his Naturalis Historia),^[35] Common Mullein was linked to witches,^[28] although the relationship remained generally ambiguous, and the plant was also widely held as being able to ward off curses and evil spirits.^[28][29][27]

The flowers provide dyes of bright yellow or green, and have been used for hair colouring.^[28][33] The dried leaves and hair were made into candle wicks, or put into shoes to help with warmth keeping. The dried stems were also dipped into suet or wax to make torches.^[28][29]

[edit] Notes

[edit] References

[edit] External links

• Microphotographies of Common Mullein
• V. thapsus bibliography