Verbascum thapsus, the great mullein, greater mullein or common mullein, is a species of mullein native to Europe, northern Africa, and Asia, and introduced in the Americas and Australia.[1]
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, and has become invasive in temperate world regions.[1] It is a minor problem for most agricultural crops, since it is not a 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.
V. thapsus is a dicotyledonous plant that produces a rosette of leaves in its first year of growth.[3][4] 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.[5] The tall, pole-like stems end in a dense spike of flowers[3] that can occupy up to half the stem length. All parts of the plants are covered with star-shaped trichomes.[5][6] This cover is particularly thick on the leaves, giving them a silvery appearance. The species' chromosome number is 2n = 36.[7]
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).[8][9] They become smaller higher up the stem,[3][4] and less strongly decurrent down the stem.[3] The flowering stem is solid and 2–2.5 cm (nearly an inch) across, and occasionally branched just below the inflorescence,[4] usually following damage.[10] After flowering and seed release, the stem and fruits usually persist in winter,[11] 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.[9]
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 1.5–3 cm (0.59–1.18 in) 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.[6][note 1] 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)[12] in size, marked with longitudinal ridges. A white-flowered form, V. thapsus f. candicans, is known to occur.[13] Flowering lasts up to three months from early to late summer (June to August in northern Europe),[4] 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.[11]
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.[note 2] The species had previously been designated as type species for Verbascum.[18] European plants exhibit considerable phenotypical variation,[19] which has led to the plant acquiring many synonyms over the years.[17][20] Introduced American populations show much less variation.[19]
The taxonomy of Verbascum has not undergone any significant revision since Svanve Mürbeck's monographs in the 1930s, with the exception of the work of Arthur Huber-Morath, who used informal grouping 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 sect. Bothrospermae subsect. Fasciculata alongside species such as Verbascum nigrum (black or dark mullein), Verbascum lychnitis (white mullein), and Verbascum sinuatum (wavy-leaved mullein).[21][22][23][24] As Verbascum thapsus is the type species of the genus the application of article 22 of the ICNafp gives sect. Verbascum subsect. Verbascum as the correct nomenclature for this placement.
V. t. crassifolium (Lam.) Murb.; Mediterranean region and to 2000 metres in southwestern Austria.[27] (syn. subsp. montanum (Scrad.) Bonnier & Layens)
V. t. giganteum (Willk.) Nyman; Spain, endemic.
In all subspecies but the type, the lower stamens are also hairy.[28] In V. t. 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.[27] In V. t. giganteum, the hairs are densely white tomentose, and lower leaves are strongly decurrent. V. t. 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.[27] Both V. t. giganteum and V. t. crassifolium were originally described as species.[3] 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.[24]
The plant is also parent to several hybrids (see table). Of these, the most common is V. × semialbum Chaub. (× V. nigrum).[7] All occur in Eurasia,[7] 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.[25][29]
Common names
V. thapsus is known by a variety of names. European reference books call it "great mullein".[30][31][32] In North America, "common mullein" is used[33][34] while western United States residents commonly refer to mullein as "cowboy toilet paper".[35][36]
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".[37] Vernacular names include innumerable references to the plant's hairiness: "woolly mullein", "velvet mullein", or "blanket mullein",[32][38] "beggar's blanket", "Moses' blanket", "poor man's blanket", "Our Lady's blanket", or "old man's blanket",[31][34][39] and "feltwort", and so on ("flannel" is another common generic name). "Mullein" itself derives from the French word for "soft".[40]
Some names refer to the plant's size and shape: "shepherd's club(s)" or "staff", "Aaron's rod"[41] (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".[31][34][42] The name "velvet dock" or "mullein dock" is also recorded, where "dock" is a British name applied to any broad-leaved plant.[43]
Distribution and habitat
V. 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.[5][44][45] In northern Europe, it grows from sea level up to 1,850 m altitude,[4] while in China it grows at 1,400–3,200 m altitude.[5]
In the United States, it was imported very early in the 18th[note 3] 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.[note 4][9][50] In 1839, it was already reported in Michigan and in 1876, in California.[9] It is now found commonly in all the states.[51] In Canada, it is most common in the Maritime Provinces and southern Quebec, Ontario, and British Columbia, with scattered populations in between.[19][52]
Great mullein most frequently grows as a colonist of bare and disturbed soil, usually on sandy or chalky ones.[7] 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.[53]
Ecology
V. thapsus grows best with little competition.
Great mullein is a biennial and generally requires winter dormancy before it can flower.[10] This dormancy is linked to starch degradation activated by low temperatures in the root, and gibberellin application bypasses this requirement.[54] Seeds germinate almost solely in bare soil, at temperatures between 10 and 40 °C.[10] 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.[10]
Seeds germinate in spring and summer. Those that germinate in autumn produce plants that overwinter if they are large enough, while rosettes less than 15 cm (6 in) across die in winter. After flowering, the entire plant usually dies at the end of its second year,[10] 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.[55] 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.[56]
A given flower is open only for a single day, opening before dawn and closing in the afternoon.[19] Flowers are self-fecundating and protogynous (with female parts maturing first),[19] 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. The flowering period of V. thapsus lasts from June to August in most of its range, extending to September or October in warmer climates.[9][10][12] Visitors include halictid bees and hoverflies.[11] The hair on lower stamens may serve to provide footholds for visitors.[19]
The fruit of great mullein contains large numbers of minute seed.
The seeds maintain their germinative powers for decades, up to 100 years, according to some studies.[57] 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,[19] with a total up to 180,000[9][10] or 240,000[12] seeds), it remains in the soil seed bank for extended periods of time, and can sprout from apparently bare ground,[10] or shortly after forest fires long after previous plants have died.[12] Its population pattern typically consists of an ephemeral adult population followed by a long period of dormancy as seeds.[19] 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.[10]
Megachilid bees of the genus Anthidium use the hair (amongst that of various woolly plants) in making their nests.[58] The seeds are generally too small for birds to feed on,[11] although the American goldfinch has been reported to consume them.[59] Other bird species have been reported to consume the leaves (Hawaiian goose)[60] or flowers (palila),[61] or to use the plant as a source when foraging for insects (white-headed woodpecker).[62] Additionally, deer and elk eat the leaves.[63]
Because it cannot compete with established plants, great mullein is no longer considered a serious agricultural weed and is easily crowded out in cultivation,[19] except in areas where vegetation is sparse to begin with, such as Californian semidesertic areas of the eastern Sierra Nevada in the USA. In such ecological contexts, it crowds out native herbs and grasses; its tendency to appear after forest fires also disturbs the normal ecological succession.[10][12] Although not an agricultural threat, its presence can be very difficult to eradicate and is especially problematic in overgrazed pastures.[9][10][12] The species is legally listed as a noxious weed in the US state of Colorado (class C)[65] and Hawaii,[66] and the Australian state of Victoria (regionally prohibited in the West Gippsland region, and regionally controlled in several others).[67]
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),[68]Gymnaetron tetrum (whose larva consume the seeds), and the mullein moth (Cucullia verbasci).[9] Useful insects are also hosted by great mullein, including predatory mites of the genera Galendromus, Typhlodromus, and Amblyseius, the minute pirate bugOrius tristicolor,[68] and the mullein plant bug (Campylomma verbasci).[70] 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.[71][72] 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.[73]
Because of ample irritating hair, V. 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 ultimately ineffective, as it only creates new bare areas for seedlings to occupy.[9][10][12]G. tetrum and Cucullia verbasci usually have little effect on V. thapsus populations as a whole.[12] Goats and chickens have also been proposed to control mullein.[10] Effective (when used with a surfactant) contact herbicides include glyphosate,[9][12]triclopyr[9] and sulfurometuron-methyl.[12] Ground herbicides, like tebuthiuron, are also effective, but they result in bare ground – ideal conditions for growing more mullein – and therefore require repeated application to prevent regrowth.[10]
"Verbasci flos": dried flowers of V. thapsus as used in herbal tea
Although long used in herbal medicine, no drugs are manufactured from its components.[2]Dioscorides first recommended the plant 2000 years ago, considering it useful as a folk medicine for pulmonary diseases.[75] Leaves were smoked to attempt to treat lung ailments, a tradition that in America was rapidly transmitted to Native American peoples.[31][76] 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.[77] All preparations meant to be drunk have to be finely filtered to eliminate the irritating hairs.[54]
The plant has been used in an attempt to treat colds, croup, sunburn, and other skin irritations.[81]
Other uses
Roman soldiers are said to have dipped the plant stalks in grease for use as torches. Other cultures use the leaves as wicks.[81] Native Americans and American colonists lined their shoes with leaves from the plant to keep out the cold.[81][31][76]
Due to its weedy capacities, the plant, unlike other species of the genus (such as V. phoeniceum), is not often cultivated.[1]
Notes
^They are all hairy in subspecies V. crassifolium and V. giganteum.
^The lectotypification is usually attributed to Arthur Huber-Morath (1971) Denkschriften der Schweizerischen Naturforschenden Gesellschaft 87:43. Some disagree since Huber-Morath did not specifically cite sheet 242.1, and credit instead L. H. Cramer, in Dassanayake & Fosberg (1981) A Revised Handbook to the Flora of Ceylon 3:389.[17]
^The 1630 number in Mitch may be a typo: the beginning of the 18th century is cited in other sources.[9][19]
^Eaton went so far as to write: "When botanists are so infatuated with wild speculation, as to tell us the mullein was introduced, they give our youngest pupils occasion to sneer at their teachers."[13]
^In book 25, Pliny describes "two principal kinds [of verbascum]" thought to be V. thapsus and V. sinuatum. The precise attribution of a third kind is unclear.[82]
^ abc"Mullein". Drugs.com. 23 November 2020. Retrieved 7 February 2021.
^ abcdeFerguson, Ian Keith (1972). "V. thapsus". In Tutin, Thomas Gaskell; et al. (eds.). Flora Europaea. Vol. 3: Diapensiaceae to Myoporaceae. Cambridge: Cambridge University Press. p. 211. ISBN0-521-08489-X.
^ abcdeBlamey, M., & Grey-Wilson, C. (1989). Flora of Britain and Northern Europe. Hodder & Stoughton, ISBN0-340-40170-2.
^ abcdefghijPitcairn, Michael. "Verbascum thapsus". Invasive Plants of California's Wildland. California Invasive Plant Council. Archived from the original on 2011-03-12. Retrieved 2009-11-06.
^ abPennel, Francis Whittier (1935). The Scrophulariaceae of eastern temperate North America. Philadelphia: George W. Carpenter Fund. pp. 173–174. OCLC852625.
^ abCarnoy, A. (1959). Dictionnaire étymologique des noms grecs de plantes (in French). Louvain: Publications Universitaires. OCLC3284108.
^Natural History Museum (2022). "Verbascum thapsus". Linnaean Plant Name Typification Project. Natural History Museum. doi:10.5519/qwv6u7j5. Retrieved 2009-11-06.
^Sotoodeh, Arash (2014). "Verbascum oreophilum var. oreophilum and Verbascum cheiranthifolium var. asperulum (Scrophulariaceae) two new records for the flora of Iran". Phytotaxa. 178 (3): 205–210. doi:10.11646/phytotaxa.178.3.6. S2CID86267331.
^Sotoodeh, Arash; Civeyrel, L.; Attar, F. (19 March 2015). "Verbascum shahsavarensis (Scrophulariaceae), a new species for Flora of Iran". Phytotaxa. 203 (1): 76. doi:10.11646/phytotaxa.203.1.8.
^Attar, Farideh; et al. (2007). "Micromorphological studies on Verbascum (Scrophulariaceae) in Iran with emphasis on seed surface, capsule ornamentation and trichomes". Flora – Morphology, Distribution, Functional Ecology of Plants. 202 (2): 169–175. doi:10.1016/j.flora.2006.04.001.
^ abBenedí Gonzalez, Carles (2009). "Verbascum"(PDF). Flora Iberica (in Spanish). Vol. XIII: Plantaginaceae-Scrophulariaceae. Madrid: Real Jardín Botánico. pp. 49–97. ISBN978-84-00-08747-0. Archived from the original(PDF) on 2011-05-13.
^ abKartesz, John (1994). A synonymized checklist of the vascular flora of the United States, Canada, and Greenland (Volume 1: Checklist). Portland, Oregon: Timber Press. p. 588. ISBN0-88192-204-8.
^Natural History Museum (2022). "Verbascum × thapsi". Linnaean Plant Name Typification Project. Natural History Museum. doi:10.5519/qwv6u7j5. Retrieved 2007-05-14.
^ abcSchmeil, Otto; Fitschen, Jost; Seybold, Siegmund (2006). Flora von Deutschland, 93. Auflage. Wiebelsheim: Quelle & Meyer Verlag. p. 496. ISBN3-494-01413-2.
^Niering, William A. (1979). The Audubon Society field guide to North American wildflowers, eastern region. New York: Knopf. p. 798. ISBN0-394-50432-1.
^ abcHarold William Rickett, ed. (1966). "The Mulleins (Verbascum)". Wild Flowers of the United States. Vol. 1. The Northeastern States (Part 2). New York: McGraw-Hill. p. 389. LCCN66017920.
^"Beyond the River". Texas Parks & Wildlife Magazine. Dale Weisman. Retrieved 2010-06-26.
^"BIO 406D-Native Plants"(PDF). An Introduction to the Flora of Central Texas. Michael Gruenstaeudl. Retrieved 2010-06-26.
^Britton, Nathaniel A.; Addison Brown (1979). "Illustrated Flora of the Northern United States and Canada". An illustrated flora of the northern United States and Canada. Vol. 3. Gentianaceae to Compositae. New York: Dover Publications. p. 175. ISBN0-486-22644-1.
^Brako, Lois; Rossman, Amy Y.; Farr, David F. (1995). Scientific and common names of 7,000 vascular plants in the United States. St. Paul, Minnesota: APS Press. p. 189. ISBN0-89054-171-X.
^"Verbascum thapsus". Global Invasive Species Database. IUCN Invasive Species Specialist Group. 8 July 2005. Archived from the original on 2009-07-15. Retrieved 2009-11-06.
^"Verbascum thapsus". Pacific Island Ecosystems at Risk. Hawaiian Ecosystems at Risk project. February 19, 2007. Retrieved 2009-11-06.
^"Verbascum thapsus". NatureServe Explorer. Archived from the original on 2008-05-11. Retrieved 2009-11-06.[], retrieved December 29, 2006.
^Parker, Ingrid M.; Joseph Rodriguez; Michael E. Loik (February 2003). "An Evolutionary Approach to Understanding the Biology of Invasions: Local Adaptation and General-Purpose Genotypes in the Weed Verbascum thapsus". Conservation Biology. 17 (1): 59–72. Bibcode:2003ConBi..17...59P. doi:10.1046/j.1523-1739.2003.02019.x. S2CID18289261.
^Reinartz, James A. (November 1984). "Life History Variation of Common Mullein (Verbascum Thapsus): I. Latitudinal Differences in Population Dynamics and Timing of Reproduction". The Journal of Ecology. 72 (3): 897–912. Bibcode:1984JEcol..72..897R. doi:10.2307/2259539. ISSN0022-0477. JSTOR2259539.
^Reinartz, James A. (November 1984). "Life History Variation of Common Mullein (Verbascum Thapsus): III. Differences Among Sequential Cohorts". The Journal of Ecology. 72 (3): 927–936. Bibcode:1984JEcol..72..927R. doi:10.2307/2259541. JSTOR2259541.
^Kivilaan, A.; Robert S. Bandurski (October 1981). "The One Hundred-Year Period for Dr. Beal's Seed Viability Experiment". American Journal of Botany. 69 (9): 1290–1292. doi:10.2307/2443054. ISSN0002-9122. JSTOR2443054.
^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.
^Banko, Paul C. et al. (2002). Palila (Loxioides bailleui), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornitholog.
^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.
^Reiner, Ralph E. (1969). Introducing the Flowering Beauty of Glacier National Park and the Majestic High Rockies. Glacier Park, Inc. p. 42.
^The History of the British Flora, A Factual Basis for Phytogeography by Sir Harry Godwin, Cambridge University Press, Cambridge, ISBN0 521 20254 X, 1975 edition page 318
^Sanchez, Juan Antonio; David R. Gillespie; Robert R. McGregor (November 2003). "The effects of mullein plants (Verbascum thapsus) on the population dynamics of Dicyphus hesperus (Heteroptera: Miridae) in tomato greenhouses". Biological Control. 28 (3): 313–319. Bibcode:2003BiolC..28..313S. doi:10.1016/S1049-9644(03)00116-6.
^ abcdeHanrahan, Claire; Rebecca J. Frey (2005). "Mullein". In Jacqueline L. Longe (ed.). The Gale encyclopedia of alternative medicine. Vol. 3: L-R (2nd ed.). Detroit: Thomson Gale. ISBN0-7876-7427-3. Archived from the original on July 15, 2009. Retrieved 2006-11-30.
^Drury, Susan (1991). "Plants and Wart Cures in England from the Seventeenth to the Nineteenth Century: Some Examples". Folklore. 102 (1): 97–100. doi:10.1080/0015587X.1991.9715809. JSTOR1260360.
^Turker, Arzu Ucar; N. D. Camper (October 2002). "Biological activity of common mullein, a medicinal plant". Journal of Ethnopharmacology. 82 (2–3): 117–125. doi:10.1016/S0378-8741(02)00186-1. PMID12241986.
^"Mullein flower". The Commission E Monographs. American Botanical Council. February 1, 1990. Archived from the original on 2006-05-11. Retrieved 2009-11-06.
^ abcNiering, William A.; Olmstead, Nancy C. (1985) [1979]. The Audubon Society Field Guide to North American Wildflowers, Eastern Region. Knopf. p. 653. ISBN0-394-50432-1.
