Verbascum thapsus L., Great Mullein

Account Summary

Growth form and preferred habitats

This large, deep tap-rooted, conspicuous, monocarpic, biennial or rarely annual plant produces a low vegetative rosette up to 60 cm in diameter that overwinters and in the succeeding summer it develops a strikingly stout, erect, flowering stem, 0.3-2.0 m tall, densely covered with soft, white hairs. In fact, the whole plant, stem and leaves, is covered with a dense, greyish or whitish, felt-like, woolly tomentum of long, soft, rarely shortly branched, hairs (Ross-Craig 1966, Part xxii, plate 1). The flowering stem is also longitudinally ridged by the decurrent bases of the stem leaves. The lower, radical, rosette leaves are alternate, oblong or oblanceolate, 10-40 cm long, their bases again decurrent on the internode below.

The tall flowering stem with its tiered decurrent leaves, their wing-like margins running down the stem, provides a means of channelling rainwater from above down to the roots. The upper leaves droop at their tips and discharge rainwater into the channelled midribs of the leaves below them that then act like gutters, so that water eventually trickles its way down the entire height of the plant using the decurrent leaf-bases, until it reaches the roots. This is an important adaptation as the species mostly occupies open, ± disturbed, ungrazed ground with well-drained or dry soils (Melderis & Bangerter 1955).

In Britain, Great Mullein is a frequent plant of rough grassland, hedge banks, roadsides, near quarries, railway sides and waste ground, preferring warm, dry, open, recently disturbed or bare, sandy, stony, rocky or calcareous soils that are moderately fertile and ungrazed. It can sometimes also grow on walls (Sinker et al. 1985).

The dense coat of felted leaf hairs makes V. thapsus foliage unpalatable to stock animals such as cattle, the hairs setting off intense irritation in the mucous membranes of the grazing animal, so they quickly learn to avoid the plant. The hairs also protect the plant from grazing by some phytophagous insects (Grieve 1931; Gross & Werner 1978). When preparing the useful Mullein Tea, a remedy of the greatest antiquity for coughs and colds, it must always be strained through fine muslin to remove any hairs that may be floating in the hot water that has been poured over the flowers, or leaves, as otherwise they cause intolerable itching in the mouth (Grieve 1931).

The felted hairs also protect the species from aqueous solutions of the herbicide 2, 4-D as the water droplets cannot penetrate the leaf surface (Gross & Werner 1978).

The established strategy of V. thapsus is categorised as SR/CSR, meaning it is intermediate between a Stress-tolerant Ruderal and a more balanced mix of all three strategies, Competitor, Stress-tolerator and Ruderal (Grime et al. 1988, 2007).

Variation

V. thapsus is described as a polymorphic species by Hultén & Fries (1986) and they mention the ease with which it becomes involved in hybridisation. Stace et al. (2015) list a total of seven rare hybrids involving V. thapsus, none of which has ever been recorded in Ireland.

The variation in Europe is sufficient for three subspecies to be recognised in Flora Europaea 3, these being: subsp. thapsus, throughout the range of the species; subsp. crassifolium (Lam.) Murb., mountains of S & C Europe, from Portugal to the E Alps; and subsp. giganteum (Willk.) Nyman, mountains of S & SE Spain (I.K. Ferguson, in: Tutin et al. 1972).

There are no subspecies presently recorded in B & I (Sell & Murrell 2007).

Fossil record and the question of native status

There is no fossil pollen record of V. thapsus at all and Godwin (1975) mentions only two seed occurrences, the first in the very early Cromer Forest Beds and the second in the Ipswichian interglacial which long predates the current Flandrian (or in Ireland, Littletonian) interglacial. Therefore, there is no relevant, direct evidence of fossil support for native status in B & I and other circumstantial evidence, either way native/introduction, must be sought to resolve or illuminate the question (Webb 1985).

The fact that V. thapus is a weedy, colonising species of disturbed ground, very long persistent in the soil seed bank and has been widely used for many years – throughout recorded history and in Classical times – in herbal medicine for both man and beast, and cultivated for this reason in Irish and E & SE England cottage gardens, sometimes on a considerable commercial scale (Allen & Hatfield 2004), suggests that man has had an important role in its introduction, increase and spread across Europe and B & I.

The genus has many species, some more suitable for garden cultivation than others, but all are acknowledged as, "Stately plants, mostly of biennial duration, but the best are so handsome and long flowering as to be quite essential in the garden." (Robinson 1909). The current author (RSF) is not suggesting that V. thapsus has been grown for decorative reasons, although this is not an impossibility since it is a very notable, sizeable, striking plant, but it certainly has been cultivated for medicinal use, probably until the late 19th century at the very least.

Phenology and flowering reproduction

V. thapsus germinates in early spring and forms a leaf rosette that continues to grow into late autumn and then overwinters. After a cold vernalisation period, in the following spring the plant produces a tall flower stalk. Flowering begins in late June and peaks in early August. The inflorescence is a very dense, spike-like raceme, 20-50 × 3 cm. Rarely, additional axillary racemes develop from the upper leaves.

Flowers mature on the inflorescence stalk from the bottom to the top in successive spirals, so that at any one point in time they appear in a loose spiral pattern up the length of the raceme. As the flowering season progresses, each successive spiral of blossoms begins slightly higher on the stem, but it overlaps for most of its length with the earlier spirals. Growth of the inflorescence stalk is indeterminate and since the duration of the flowering period is a function of stalk height, taller stalks can continue flowering into the autumn (late September or early October).

The flowers are large, sessile, bisexual and only slightly irregular. Each flower is subtended by a prominent green bract. The calyx is deeply 5-lobed, the lobes narrowly lanceolate. The corolla is 'regular' rotate (ie symmetrical, not irregular), with a very short tube and five broad, spreading lobes, 20-35 mm in diameter, pale yellow, or rarely white and with five irregular stamens directly attached to it (ie they are epipetalous). The three upper filaments are shorter, clothed with dense, yellowish or white-woolly hairs and their anthers are reniform (ie kidney-shaped) and medifixed, while the lower two stamens have longer, glabrous filaments. The lower pair of anthers are large, elongate, coloured, obliquely attached and produce a copious supply of pollen. The flowers produce very little or no nectar. The superior ovary is 2-celled and is surmounted by a solitary style, topped by a club-shaped, capitate stigma (I.K. Ferguson, in: Tutin et al. 1972; Hickey & King 1981; Stace et al. 2015).

The individual flowers of V. thapsus are ephemeral, opening before dawn and closing around mid-afternoon of the same day. They are protogynous, the style maturing first before the anthers and then bending downwards once the anthers appear. The two anterior stamen filaments are naked and they produce most of the pollen that leads to fertilisation. The woolly hairs on the filaments of the posterior three stamens appear to provide a useful platform foothold for insect visitors such as hoverflies and bees that gather pollen from the posterior anthers while their abdomens are dusted with pollen from the anterior pair. Although visited by a wide variety of insects, including butterflies, moths and flies (Fitter 1987), it is said that only long- and short-tongued bees are effective vectors carrying out cross-pollination (Pennell 1935). Since there is very little or no nectar in the flowers, this latter claim appears open to question and the current author (RSF) expresses his doubt on the matter.

Verbascum is an unusual genus in that the stigma is not merely passive but, rather, is active when it comes to pollen capture. In Verbascum, and also in Acanthus, the stigma is like a valve, opening only when it is receptive and closing again shortly after pollen is deposited upon it (Percival 1965).

Towards the end of the day (ie usually mid-afternoon), if cross-pollination has not occurred, the style returns to its original position and the corolla closes, pushing the still receptive stigma against the anthers and effecting self-pollination (ie autogamy takes place) (Kerner von Marilann 1895).

The fruit is a capsule, 3-6 mm long, ovoid, longer than the calyx and very hard. It splits into two valves at maturity to release the numerous minute seeds which are columnar, truncate, light to dark brown, 0.5-1.0 mm long, their lateral surfaces angular, six-sided and rugose with blunt tubercles in vertical rows (Butcher 1961; Hutchinson 1972).

Seed production, dispersal and longevity

Seed production can be very large, but it is also extremely variable, ultimately depending to a great extent upon the scale of the plant and size of the inflorescence. Salisbury (1942) reports the mean number of capsules per plant as 226 ± 42, with an average of 596 ± 30 seeds per capsule. This gives an approximate average of 136,000 seeds per plant. The number of seeds for a population from a three year old Michigan field in August 1976 ranged from 0 to 749 per capsule, with a mean of 208 ± 200 for a total of 175,000 per plant. The extreme variation in this latter example was caused by weevil predation (Gross & Werner 1978).

Seeds possess no specialised morphological adaptations for dispersal by wind or animals, but they are tiny, very hard and produced in abundance. The fruit capsule splits open along its long axis when mature and any slight movement of the tall flowering stalk by wind or a large animal is all that is required to release the seeds from the parent (Mclean & Ivimey-Cook 1956).

Seeds are dispersed as far as 11 m, although 93% of them fall within 5 m and 75% of them fall within 1 m of the parent plant (Salisbury 1964; Gross & Werner 1978).

Seed of V. thapsus is capable of immediate germination upon release, there being no embryo after-ripening requirement (Gardner 1921). Buried dormant seed survival in soil is long-term persistent, viable seed having germinated after periods of 38 years or much longer. Seed in Denmark from soil levels archaeologically dated to 1300 AD were still viable (Oosting & Humphreys 1940; Ødum 1965; Thompson et al. 1997).

Fermanagh occurrence

An occasional casual in Fermanagh, Great Mullein is only sporadically found in gardens, waste ground, walls and disturbed soil. Although the plentifully produced wind-dispersed seed is long-persistent in the soil seed bank (Salisbury 1942, pp. 126-7), it is hardly persistent in any site within the VC. V. thapsus has been recorded in 19 tetrads and, as the map indicates, they are thinly scattered in the centre and southern half of Fermanagh, generally in sites near habitation. Seventeen of the tetrads have post-1975 records.

Irish occurrence

Rare and local in Ireland, Great Mullein is listed in the Cen Cat Fl Ir 2 as occurring at least once in every Irish VC except W Donegal (H35). In the past, it has been presumed native throughout the island. It is a locally frequent colonist in stony or sandy banks, seashores and bare waste places in the southern half of Ireland, but is very much rarer in the north of the island. The rare, sporadic, casual occurrence in Fermanagh and elsewhere in NE Ireland (FNEI 3), leads the current author (RSF) to believe it is much more likely to represent an alien here. The occasional, somewhat more clumped occurrence in adjacent Co Tyrone (H36), mostly on waste ground and dumps in the SE and NW of the VC, is not dissimilar to the Fermanagh experience and, again, McNeill (2010) considers Great Mullein an introduction.

British occurrence

There are six British species of Verbascum and natural hybrids between most of them are not uncommon. V. thapsus is widely distributed throughout England and Wales but it becomes scarce northwards and it is rare and local in Scotland. It should also be noted that it is absent from the Outer Hebrides (VC 110) and Shetland (VC 112) and is recognised as an alien introduction in both Orkney (VC 111) and the Isle of Man (VC 71) (A. Horsfall, in: Preston et al. 2002).

European and world occurrence

V. thapsus belongs to the Eurosiberian temperate phytogeographical element. It is distributed across most of Europe except the extreme north and much of the Balkan Peninsula. It is also present in Asia south to the Caucasus and Himalaya and eastwards to W China. It is introduced and widely naturalised across N America and is present in Argentina, Patagonia and the islands of New Zealand, Hawaii and Réunion (Hultén & Fries 1986, Map 1629).

Uses

It is probably the case that all the various Mullein species found in Britain possess similar medicinal properties. Stace (2019) lists 13 species plus 20 hybrids, most of which being garden escapes would be of very limited distribution (New Atlas; Stace et al. 2015). Of the more common and significantly available and useful species, V. thapsus is by far the one most employed (Grieve 1931). For medicinal purposes, it is generally collected from the wild, although in Ireland where it is much more scarce in comparison with England and Wales, it was carefully cultivated in gardens because of a steady demand for the plant by sufferers from pulmonary consumption (Grieve 1931).

The leaves and flowers are the parts used medicinally. The leaves are nearly odourless and are of a mucilaginous and bitter taste while the flowers are slightly more agreeable in flavour. The plant has very marked demulcent, emollient and astringent properties that make them useful in herbal medicine for the treatment of both pectoral complaints and bleeding of the lungs and bowels. It was greatly valued for the treatment of consumption. The herb was also used to treat the pain and irritation of haemorrhoids and an infusion was given to treat diarrhoea and bleeding of the bowels (Grieve 1931).

Use in cattle included treatment for strangury (difficulty in passing urine), for which finely chopped Mullein leaves were mixed with bran and water fed to the animals (Vickery 2019).

In continental Europe, a sweetened infusion of the flowers, strained in order to remove the rough hairs, was frequently used as a domestic remedy in mild catarrhs and colic. A conserve of the flowers was also employed against ringworm and a distilled water of the flowers was long reputed to be a cure for burns. These, and many other herbal medicinal uses, plus reports of various other non-medicinal uses, for instance as a yellow dye, sometimes used as a hair dye, and as a fish intoxicant, the seeds being slightly narcotic, have been documented by Grieve (1931)! Vickery (2019) mentions finds of V. thapsus at Mount Grace Priory in N Yorkshire after an archaeological dig and the possibility that monks based there would have used the dried flower stalks of Mullein, which were dipped in tallow to make wicks for processional candles. This religious establishment was dissolved in 1539, but Vickery warns that the idea that the Mount Grace plants grew from 16th century seed is probably no more than wishful thinking.

Names

The genus name 'Verbascum' is the classical Latin name of an unknown plant in the Roman writer Pliny's works borrowed and reused for this group of plants (Gilbert-Carter 1964; Gledhill 1985). Another suggested origin is that it might be a corruption of the Latin 'barbascum', meaning 'a hairy plant', from 'barba', 'a beard', many of the members of the genus being characterised by the possession of downy foliage (Johnson & Smith 1946). The Latin specific epithet 'thapsus' is after the town of that name in ancient Africa (now Tunisia), or after the Greek island Thapsos (Johnson & Smith 1946; Gledhill 1985).

No less than 50 English common names are listed by Grigson (1955, 1987) and 43 by Vickery (2019), many of them containing the word elements 'flannel' or 'blanket', clear references to the soft, woolly hairs that cover the plant. Names that suggest everything that 'soft' include references to Rabbit's ears, Donkey's ears, velvet, rag paper and flannel. Other names contain elements such as 'candle' and 'taper' which refer to the use of the dried plant as kindling, or as lighting when dipped in suet or wax.

The most frequently used name 'Mullein' dates from the 15th century from the French 'moleine', possibly from 'mol' ('mou'), meaning 'soft' (from the Latin 'mollis'), an obvious reference to the conspicuously soft, felted leaves (Grigson 1974). The French 'moleine', from the Old French 'malen' and the Latin 'malandrium', refers to the scab disease in cattle and to the 'malanders' or leprosy. 'Malandre' also refers to other diseases in cattle, including lung problems (Prior 1879). The name 'Mullein' was spelt variously by early herbal writers, eg 'Moleyne' (Grete Herball, Anonymous (1526)), 'Mollen' (Turner (1568) A New Herbal), 'Mullen' (Turner (1548) Names of herbs), 'Mulleyne' (Lyte (1578) A Niewe Herball, or Historie of Plantes). Gerard also has 'Mullein' or rather 'Woolen', a reference to the generally woolly appearance of the plant (Britten & Holland 1886).

Threats

None.

• Find out more about the format of the species accounts
• View abbreviations
• View references for all species accounts
• View a gazetteer of all the sites