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Verbascum thapsus

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Verbascum thapsus, the great mullein or common mullein, is a species of mullein native to Europe, northern Africa, and Asia, and introduced in the Americas and Australia.

It is a hairy biennial plant that can grow to 2 m tall or more. Its small, yellow flowers are densely grouped on a tall stem, which grows from a large rosette of leaves. It grows in a wide variety of habitats, but prefers well-lit, disturbed soils, where it can appear soon after the ground receives light, from long-lived seeds that persist in the soil seed bank. It is a common weedy plant that spreads by prolifically producing seeds, but it rarely becomes aggressively invasive, since its seeds require open ground to germinate. It is a very minor problem for most agricultural crops, since it is not a very competitive species, being intolerant of shade from other plants and unable to survive tilling. It also hosts many insects, some of which can be harmful to other plants. Although individuals are easy to remove by hand, populations are difficult to eliminate permanently.

It is widely used for herbal remedies, with well-established emollient and astringent properties. Mullein remedies are especially recommended for coughs and related problems, but also used in topical applications against a variety of skin problems. The plant has also been used to make dyes and torches.

Description

A stemless rosette in Hawaii

V. thapsus is a dicotyledonous plant that produces a rosette of leaves in its first year of growth.<ref name="FlEu">Template:Cite encyclopedia</ref><ref name="blamey">Blamey, M., & Grey-Wilson, C. (1989). Flora of Britain and Northern Europe. Hodder & Stoughton, Template:ISBN.</ref> The leaves are large, up to 50 cm long. The second-year plants normally produce a single unbranched stem, usually 1–2 m tall. In the eastern part of its range in China, it is, however, only reported to grow up to 1.5 m tall.<ref name="china">Template:Cite web</ref> The tall, pole-like stems end in a dense spike of flowers<ref name="FlEu"/> that can occupy up to half the stem length. All parts of the plants are covered with star-shaped trichomes.<ref name="china"/><ref name="jepson">Template:Cite web</ref> This cover is particularly thick on the leaves, giving them a silvery appearance. The species' chromosome number is 2n = 36.<ref name="NWeurope"/>

On flowering plants, the leaves are alternately arranged up the stem. They are thick and decurrent, with much variation in leaf shape between the upper and lower leaves on the stem, ranging from oblong to oblanceolate, and reaching sizes up to 50 cm long and 14 cm across (19 inches long and 5 inches wide).<ref name="huxley">Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan. Template:ISBN</ref><ref name="remaley"/> They become smaller higher up the stem,<ref name="FlEu"/><ref name="blamey"/> and less strongly decurrent down the stem.<ref name="FlEu"/> The flowering stem is solid and 2–2.5 cm (nearly an inch) across, and occasionally branched just below the inflorescence,<ref name="blamey"/> usually following damage.<ref name="Hoshovsky">Template:Cite web</ref> After flowering and seed release, the stem and fruits usually persist in winter,<ref name="illinois"/> drying into dark brown, stiff structures of densely packed, ovoid-shaped, and dry seed capsules. The dried stems may persist into the following spring or even the next summer. The plant produces a shallow taproot.<ref name="remaley"/>

A closeup of the flowers

Flowers are pentamerous with (usually) five stamen, a five-lobed calyx tube and a five-petalled corolla, the latter bright yellow and an Template:Convert wide. The flowers are almost sessile, with very short pedicels (2 mm, 0.08 in). The five stamens are of two types, with the three upper stamens being shorter, their filaments covered by yellow or whitish hairs, and having smaller anthers, while the lower two stamens have glabrous filaments and larger anthers.<ref name="jepson"/><ref group="note">They are all hairy in subspecies V. crassifolium and V. giganteum.</ref> The plant produces small, ovoid (6 mm, 0.24 in) capsules that split open by way of two valves, each capsule containing large numbers of minute, brown seeds less than 1 mm (0.04 in)<ref name="davis"/> in size, marked with longitudinal ridges. A white-flowered form, V. thapsus f. candicans, is known to occur.<ref name="pennel"/> Flowering lasts up to three months from early to late summer (June to August in northern Europe),<ref name="blamey"/> with flowering starting at the bottom of the spike and progressing irregularly upward; each flower opens for part of a day and only a few open at the same time around the stem.<ref name="illinois"/>

Taxonomy

For the purpose of botanical nomenclature, Verbascum thapsus was first described by Carl Linnaeus in his 1753 Template:Lang. The specific epithet thapsus had been first used by Theophrastus (as Template:Lang, Template:Lang)<ref name="carnoy"/> for an unspecified herb from the Ancient Greek settlement of Thapsos, near modern Syracuse, Sicily,<ref name="carnoy">Template:Cite book</ref><ref>Template:Sv icon Den virtuella Floran: Verbascum thapsus, retrieved on November 6, 2009.</ref> though it is often assimilated to the ancient Tunisian city of Thapsus.<ref>Template:Cite web</ref>

At the time, no type specimen was specified, as the practice only arose later, in the 19th century. When a lectotype (type selected amongst original material) was designated, it was assigned to specimen 242.1 of Linnaeus' herbarium, the only V. thapsus specimen.Template:Refn The species had previously been designated as type species for Verbascum.<ref>Template:Cite web</ref> European plants exhibit considerable phenotypical variation,<ref name="BoCW"/> which has led to the plant acquiring many synonyms over the years.<ref name="florida-atlas"/><ref>Template:Cite web</ref> Introduced American populations show much less variation.<ref name="BoCW"/>

The taxonomy of Verbascum has not undergone any significant revision since Svanve Mürbeck's monographies in the 1930s, with the exception of the work of Arthur Huber-Morath, who used informal group in organizing the genus for the florae of Iran and Turkey to account for many intermediate species. Since Huber-Morath's groups are not taxonomical, Mürbeck's treatment is the most current one available, as no study has yet sought to apply genetic or molecular data extensively to the genus. In Mürbeck's classification, V. thapsus is placed in section Bothrospermae subsect. Fasciculata (or sect. Verbascum subsect. Verbascum depending on nomenclatural choices) alongside species such as Verbascum nigrum (black or dark mullein), Verbascum lychnitis (white mullein) and Verbascum sinuatum (wavy-leaved mullein).<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="iberica"/>

Subspecies and hybrids

Hybrids of Verbascum thapsus<ref name="NWeurope">Template:Cite web</ref><ref name="kartesz">Template:Cite book</ref>
Hybrid name Other
parent species
Notes
V. × duernsteinense Teyber V. speciosum
V. × godronii Boreau V. pulverulentum
V. × kerneri Fritsch V. phlomoides
V. × lemaitrei Boreau V. virgatum
V. × pterocaulon Franch. V. blattaria
V. × thapsi L. V. lychnitis syn. V. × spurium
W.D.J.Koch, may be a
nomen ambiguum<ref>Template:Cite web</ref>
V. × semialbum Chaub. V. nigrum
none V. pyramidatum

There are three usually recognized subspecies:

  • V. thapsus subsp. thapsus; type, widespread.
  • V. thapsus subsp. crassifolium (Lam.) Murb.; Mediterranean region and to 2000 metres in southwestern Austria.<ref name=schmeil/> (syn. subsp. montanum (Scrad.) Bonnier & Layens)
  • V. thapsus subsp. giganteum (Willk.) Nyman; Spain, endemic.

In all subspecies but the type, the lower stamens are also hairy.<ref>Template:Cite web</ref> In subsp. crassifolium, the hairiness is less dense and often absent from the upper part of the anthers, while lower leaves are hardly decurrent and have longer petioles.<ref name=schmeil>Template:Cite book</ref> In subsp. giganteum, the hairs are densely white tomentose, and lower leaves strongly decurrent. Subsp. crassifolium also differs from the type in having slightly larger flowers, which measure 15–30 mm wide, whereas in the type they are 12–20 mm in diameter.<ref name=schmeil/> Both subsp. giganteum and subsp. crassifolium were originally described as species.<ref name="FlEu"/> Due to its morphological variation, V. thapsus has had a great many subspecies described. A recent revision led its author to maintain V. giganteum but sink V. crassifolium into synonymy.<ref name="iberica">Template:Cite encyclopedia</ref>

The plant is also parent to several hybrids (see table). Of these, the most common is V. × semialbum Chaub. (× V. nigrum).<ref name="NWeurope"/> All occur in Eurasia,<ref name="NWeurope"/> and three, V. × kerneri Fritsch, V. × pterocaulon Franch. and V. × thapsi L. (syn. V. × spurium W.D.J.Koch), have also been reported in North America.<ref name="kartesz"/><ref>Template:Cite web</ref>

Common names

V. thapsus is known by a variety of names. European reference books call it "great mullein".<ref name="jncc">Template:Cite web</ref><ref name="grieve"/><ref name="elsevier633">Watts (2000), pp. 633–634.</ref> In North America, "common mullein" is used<ref>Template:Cite book</ref><ref name="Rickett">Template:Cite encyclopedia</ref> while western United States residents commonly refer to mullein as "cowboy toilet paper".<ref name="tpwmag">Template:Cite web</ref><ref name="utexas">Template:Cite web</ref>

In the 19th century it had well over 40 different common names in English alone. Some of the more whimsical ones included "hig candlewick", "indian rag weed", "bullicks lungwort", "Adams-rod", "hare's-beard" and "ice-leaf".<ref>Template:Cite encyclopedia</ref> Vernacular names include innumerable references to the plant's hairiness: "woolly mullein", "velvet mullein" or "blanket mullein",<ref name="elsevier633"/><ref>Template:Cite book</ref> "beggar's blanket", "Moses' blanket", "poor man's blanket", "Our Lady's blanket" or "old man's blanket",<ref name="grieve"/><ref name="Rickett"/><ref>Watts (2000), pp. 108, 369.</ref> and "feltwort", and so on ("flannel" is another common generic name). "Mullein" itself derives from the French word for "soft".<ref>Template:Cite web</ref>

Some names refer to the plant's size and shape: "shepherd's club(s)" or "staff", "Aaron's Rod" (a name it shares with a number of other plants with tall, yellow inflorescences), and a plethora of other "X's staff" and "X's rod".<ref name="grieve"/><ref name="Rickett"/><ref>Watts (2000), pp. 774–775, 819–820. p. 866: "A tall plant like Mullein attracts 'staff' and 'rod' names."</ref> The name "velvet dock" or "mullein dock" is also recorded, where "dock" is a British name applied to any broad-leaved plant.<ref>Watts (2000), pp. 302, 634.</ref>

Distribution and habitat

Verbascum thapsus has a wide native range including 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 Himalayas.<ref name="china"/><ref name="flora">Flora Europaea: Verbascum thapsus, retrieved on November 6, 2009.</ref><ref name="grin">Template:GRIN</ref> In northern Europe, it grows from sea level up to 1,850 m altitude,<ref name="blamey"/> while in China it grows at 1,400–3,200 m altitude.<ref name="china"/>

It has been introduced throughout the temperate world, and is established as a weed in Australia, New Zealand, tropical Asia, La Réunion, North America, Hawaii, Chile, Hispaniola and Argentina.<ref name = "grin"/><ref>Template:Cite web</ref><ref name="ISSG">Template:Cite web</ref><ref>Template:Cite web</ref> It has also been reported in Japan.<ref>Template:Cite web</ref>

In the United States it was imported very early in the 18thTemplate:Refn century and cultivated for its medicinal and piscicide properties. By 1818, it had begun spreading so much that Amos Eaton thought it was a native plant.Template:Refn<ref name="remaley"/><ref name="mitch">Template:Cite web</ref> In 1839 it was already reported in Michigan and in 1876, in California.<ref name="remaley">Template:Cite web</ref> It is now found commonly in all the states.<ref>Template:Cite web</ref> In Canada, it is most common in the Maritime Provinces as well as southern Quebec, Ontario and British Columbia, with scattered populations in between.<ref name="BoCW"/><ref>Template:Cite web[], retrieved December 29, 2006.</ref>

Great mullein most frequently grows as a colonist of bare and disturbed soil, usually on sandy or chalky ones.<ref name="NWeurope"/> It grows best in dry, sandy or gravelly soils, although it can grow in a variety of habitats, including banksides, meadows, roadsides, forest clearings and pastures. This ability to grow in a wide range of habitats has been linked to strong phenotype variation rather than adaptation capacities.<ref>Template:Cite journal</ref>

Ecology

A Mullein plant growing in aa dry, mountainous area.
V. thapsus grows best where there is little competition.

Great mullein is a biennial and generally requires winter dormancy before it can flower.<ref name="Hoshovsky"/> This dormancy is linked to starch degradation activated by low temperatures in the root, and gibberellin application bypasses this requirement.<ref name="phyt"/> Seeds germinate almost solely in bare soil, at temperatures between 10 °C and 40 °C.<ref name="Hoshovsky"/> While they can germinate in total darkness if proper conditions are present (tests give a 35% germination rate under ideal conditions), in the wild, they in practice only do so when exposed to light, or very close to the soil surface, which explains the plant's habitat preferences. While it can also grow in areas where some vegetation already exists, growth of the rosettes on bare soil is four to seven times more rapid.<ref name="Hoshovsky"/>

Seeds germinate in spring and summer. Those that germinate in autumn produce plants that overwinter if they are large enough, while rosettes less than Template:Convert across die in winter. After flowering the entire plant usually dies at the end of its second year,<ref name="Hoshovsky"/> but some individuals, especially in the northern parts of the range, require a longer growth period and flower in their third year. Under better growing conditions, some individuals flower in the first year.<ref>Template:Cite journal</ref> Triennial individuals have been found to produce fewer seeds than biennial and annual ones. While year of flowering and size are linked to the environment, most other characteristics appear to be genetic.<ref>Template:Cite journal</ref>

A given flower is open only for a single day, opening before dawn and closing in the afternoon.<ref name="BoCW"/> Flowers are self-fecundating and protogynous (with female parts maturing first),<ref name="BoCW"/> 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. V. thapsus' flowering period lasts from June to August in most of its range, extending to September or October in warmer climates.<ref name="remaley"/><ref name="Hoshovsky"/><ref name="davis"/> Visitors include halictid bees and hoverflies.<ref name="illinois">Template:Cite web</ref> The hair on lower stamens may serve to provide footholds for visitors.<ref name="BoCW"/>

A close-up of the green capsules of V. thapsus, surrounded by the sepals
The fruit of great mullein contains large numbers of minute seed.

The seeds maintain their germinative powers for decades, up to a hundred years, according to some studies.<ref name="beal">Template:Cite journal</ref> Because of this, and because the plant is an extremely prolific seed bearer (each plant produces hundreds of capsules, each containing up to 700+ seeds,<ref name="BoCW"/> with a total up to 180,000<ref name="remaley"/><ref name="Hoshovsky"/> or 240,000<ref name="davis"/> seeds), it remains in the soil seed bank for extended periods of time, and can sprout from apparently bare ground,<ref name="Hoshovsky"/> or shortly after forest fires long after previous plants have died.<ref name="davis"/> Its population pattern typically consists of an ephemeral adult population followed by a long period of dormancy as seeds.<ref name="BoCW"/> Great mullein rarely establishes on new grounds without human intervention because its seeds do not disperse very far. Seed dispersion requires the stem to be moved by wind or animal movement; 75% of the seeds fall within 1 m of the parent plant, and 93% fall within 5 m.<ref name="Hoshovsky"/>

Megachilid bees of the genus Anthidium use the hair (amongst that of various woolly plants) in making their nests.<ref>Template:Cite book</ref> The seeds are generally too small for birds to feed on,<ref name="illinois"/> although the American goldfinch has been reported to consume them.<ref>Template:Cite journal</ref> Other bird species have been reported to consume the leaves (Hawaiian goose)<ref>Banko, Paul C., Black, Jeffrey M. and Banko, Winston E. (1999). Hawaiian Goose (Branta sandvicensis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.</ref> or flowers (palila),<ref>Banko, Paul C. et al. (2002). Palila (Loxioides bailleui), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornitholog.</ref> or to use the plant as a source when foraging for insects (white-headed woodpecker).<ref>Garrett, Kimball L., Raphael, Martin G. and Dixon, Rita D. (1996). White-headed Woodpecker (Picoides albolarvatus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.</ref>

Fossil record

Seed of Verbascum thapsus has been recorded from part of the Cromer Forest Bead series and at West Wittering in Sussex from some parts of the Ipswichian interglacial layers.<ref>The History of the British Flora, A Factual Basis for Phytogeography by Sir Harry Godwin, Cambridge University Press, Cambridge, Template:ISBN, 1975 edition page 318</ref>

Agricultural impacts and control

Because it cannot compete with established plants, great mullein is no longer considered a serious agricultural weed and is easily crowded out in cultivation,<ref name="BoCW">Template:Cite journal Reprinted in Mulligan, G.A. (1979), The Biology of Canadian Weeds I, Template:ISBN, pp. 320–331.</ref> except in areas where vegetation is sparse to begin with, such as Californian semi-desertic areas of the eastern Sierra Nevada. In such ecological contexts, it crowds out native herbs and grasses; its tendency to appear after forest fires also disturbs the normal ecological succession.<ref name="Hoshovsky"/><ref name="davis"/> Although not an agricultural threat, its presence can be very difficult to completely eradicate, and is especially problematic in overgrazed pastures.<ref name="remaley"/><ref name="Hoshovsky"/><ref name="davis">Template:Cite web</ref> The species is legally listed as a noxious weed in the American state of Colorado (Class C)<ref>Template:Cite web</ref> and Hawaii,<ref>Template:Cite web</ref> and the Australian state of Victoria (regionally prohibited in the West Gippsland region, and regionally controlled in several others).<ref>Template:Cite web</ref>

Despite not being an agricultural weed in itself, it hosts a number of insects and diseases, including both pests and beneficial insects.<ref name="horton">Template:Cite journal</ref> It is also a potential reservoir of the cucumber mosaic virus, Erysiphum cichoraceum (the cucurbit powdery mildew) and Texas root rot.<ref name="BoCW"/><ref>Template:Cite journal</ref> A study found V. thapsus hosts insects from 29 different families. 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.<ref name="horton"/>

Other insects commonly found on great mullein feed exclusively on Verbascum species in general or V. thapsus in particular. They include mullein thrips (Haplothrips verbasci),<ref name="horton"/> Gymnaetron tetrum (whose larva consume the seeds) and the mullein moth (Cucullia verbasci).<ref name="remaley"/> Useful insects are also hosted by great mullein, including predatory mites of the genera Galendromus, Typhlodromus and Amblyseius, the minute pirate bug Orius tristicolor<ref name="horton"/> and the mullein plant bug (Campylomma verbasci).<ref>Template:Cite web</ref> The plant's ability to host both pests and beneficials makes it potentially useful to maintain stable populations of insects used for biological control in other cultures, like Campylomma verbasci and Dicyphus hesperus (Miridae), a predator of whiteflies.<ref>Template:Cite web</ref><ref>Template:Cite journal</ref> A number of pest Lepidoptera species, including the stalk borer (Papaipema nebris) and gray hairstreak (Strymon melinus), also use V. thapsus as a host plant.<ref>Template:Cite web</ref>

A series of leaves are seen wrapping down the length of a stem. The leaves have thick veining and both them and the stem have a woolly appearance from the hair covering them.
Because of the plant's hirsuteness, Verbascum thapsus is resistant to grazing and contact herbicides.

Control of the plant, when desired, is best managed via mechanical means, such as hand pulling and hoeing, preferably followed by sowing of native plants. Animals rarely graze it because of its irritating hairs, and liquid 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 occupy.<ref name="remaley"/><ref name="Hoshovsky"/><ref name="davis"/> G. tetrum and Cucullia verbasci usually have little effect on V. thapsus populations as a whole.<ref name="davis"/> Goats and chickens have also been proposed to control mullein.<ref name="Hoshovsky"/> Effective (when used with a surfactant) contact herbicides include glyphosate,<ref name="remaley"/><ref name="davis"/> triclopyr<ref name="remaley"/> and sulfurometuron-methyl.<ref name="davis"/> Ground herbicides, like tebuthiuron, are also effective, but recreate bare ground and require repeated application to prevent regrowth.<ref name="Hoshovsky"/>

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, as it contains mucilage, several saponins, coumarin and glycosides. Dioscorides recommended it for diseases of the lung and it is now widely available in health and herbal stores. Non-medical uses have included dyeing and making torches.

Traditional medicine

"Verbasci flos": dried flowers of Verbascum thapsus as used in herbal tea

Dioscorides first recommended the plant 2000 years ago, for pulmonary diseases.<ref name="silverman">Template:Cite book</ref> Leaves were smoked to attempt to treat pulmonary ailments, a tradition that in America was rapidly transmitted to Native American peoples.<ref name="grieve">Template:Cite encyclopedia</ref><ref name="hanrahan">Template:Cite encyclopedia</ref> The Zuni people, however, use the plant in poultices of powdered root applied to sores, rashes and skin infections. An infusion of the root is also used to treat athlete's foot.<ref>Template:Cite journal</ref> All preparations meant to be drunk have to be finely filtered to eliminate the irritating hairs.<ref name="phyt">Template:Cite journal</ref>

Oil from the flowers was used against catarrhs, colics and, in Germany, earaches, frostbite, eczema and other external conditions.<ref name="grieve"/> Topical application of various V. thapsus-based preparations was recommended for the treatment of warts,<ref>Template:Cite journal</ref> boils, carbuncles, hemorrhoids, and chilblains, amongst others.<ref name="grieve"/><ref name="hanrahan"/> Recent studies have found that great mullein contains glycyrrhizin compounds with bactericide and potential anti-tumoral action. These compounds are concentrated in the flowers.<ref>Template:Cite journal</ref> The German Commission E sanctioned medicinal use of the plant for catarrhs.<ref>Template:Cite web</ref> It was also part of the National Formulary in the United States<ref name="hanrahan"/> and United Kingdom.<ref name="grieve"/> The plant's leaves, in addition to the seeds, have been reported to contain rotenone, although quantities are unknown.<ref name="pfaf">Template:Cite web</ref>

Other uses

Like many ancient medicinal plants (Pliny the Elder describes it in his Naturalis Historia),Template:Refn great mullein was linked to witches,<ref name="grieve"/> although the relationship remained generally ambiguous, and the plant was also widely held to ward off curses and evil spirits.<ref name="grieve"/><ref name="phyt"/><ref name="silverman"/><ref name="hanrahan"/> The seeds contain several compounds (saponins, glycosides, coumarin, rotenone) that are toxic to fish, and have been widely used as piscicide for fishing.<ref name="remaley"/><ref>Template:Cite journal</ref>

The flowers provide dyes of bright yellow or green, and have been used for hair dye.<ref name="grieve"/><ref name="pfaf"/> The dried leaves and hair were made into candle wicks, or put into shoes to help with insulating them. The dried stems were also dipped into suet or wax to make torches.<ref name="grieve"/><ref name="hanrahan"/> Due to its weedy capacities, the plant, unlike other species of the genus (such as V. phoeniceum), is not often cultivated.

The stalk can also be dried as a spindle for making fire either by hand drill or bow drill.

Notes

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References

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Bibliography

External links

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