The Great Mullein is one of the most statuesque of our native plants. In its full-grown state, the slender flowering spire reaches almost two metres, with large leaves that are furry and grey-green in colour. The spire sways gently in the slightest breeze, and the bright yellow flowers advertise themselves to passing bees and other flying insects. A rich folk history surrounds the Great Mullein, and it has served humankind as a herbal medicine for at least two thousand years. It is still quite common today, and often occurs in urban settings as shown in the picture below.
Verbascum thapsus on a doorstep in Dalkeith, Midlothian (Image, Chris Jeffree).
It belongs to the Scrophulariaceae, the Family of foxgloves, figworts and snapdragons. Great Mullein is a biennial species, forming a rosette and a deep root in its first year. After over-wintering, it mobilises its stored reserves to form the thick flowering spire and blooms in the summer of its second year. Wind and shaking disperses its numerous tiny seeds (estimated as over 100,000 per plant), then it dies.
I think my first ever encounter with this plant was beside a railway line. It is often seen on the ballast of rail tracks in southern Scotland (Braithwaite 2015) and Brian Ballinger reports it from railway stations of Easter Ross, but more generally its habitat is variously stated as “sunny banks and waste places usually on dry soil” and “waste and rough ground, banks and grassy places, mostly on sandy or chalky soils”. Averis (2013) emphasises “well-lit”, “disturbed ground” and mentions hedgerows as an additional habitat. It does not stand competition and so it is not a serious weed of arable crops. It is often seen in gardens and allotments, where it is tolerated for the interest it brings, alongside other charismatic volunteers like Teasel, Feverfew and Buddleja.
An especially well-grown specimen of V. thapsus is shown on the left (Image by Chris Jeffree).
It is native to Europe and most of Asia but it has spread to other parts of the world, including North America, South America and Australasia. In North America it was introduced for medicinal use and also as a piscicide in the mid 1700’s by a few families in the Blue Ridge Mountains of Virginia. To kill fish, crushed seeds were mixed with water and thrown into relatively still waters, as described by Wilhelm (1974). The use of Verbascum in fishing was widespread in Europe and Asia in earlier times. Colonists took Verbascum seeds from Europe to catch fish.
The active fish-killing ingredient in Mullein is a compound called rotenone. It is a pesticide, insecticide and a piscicide (it is also found in many leguminous species, especially in the genus Derris). It is less poisonous to humans but it has been implicated in causing symptoms of Parkinson’s Disease in fish farmers. In the UK, rotenone insecticides (sold under the trade name Derris) were banned for sale in 2009.
The most complete sources of information on this plant are from USA and Canada (Gross and Werner 1978). These authors point out that eight of the 250 European species of Verbascum have been introduced into North America, but V. thapsus is the most common. Ansari and Daehler (2000 ) of the University of Hawaii at Manoa describe how the species has spread rapidly in Hawaii where its tolerance of competing vegetation seems to be higher than elsewhere. They also review the remarkable data on the longevity of seeds in the soil. There are well authenticated records of its germination after decades of burial. I have so far not been able to find the book, Germination of Ancient Seeds, where the claim is made of viable seeds of V. thapsus from soil samples archeologically dated as 1300 AD (Odum 1965).
The flower-parts are in fives (5 stamens, 5-lobed calyx and 5 petals forming the flower). The three upper stamens are shorter, covered by yellow or whitish hairs, The flower itself is bright yellow (rarely white) and 1.5–3 cm wide. Each flower lasts for one day only. Pollination is by bees. Self-pollination may occur at the end of the day if the flowers are not cross‑pollinated. Image: Chris Jeffree.
The general hairiness and soft ‘feel’ of the leaves is remarkable, and is presumed to defend the leaves against attack by herbivores (small and large). The softness and ‘handy’ size has prompted some people to call it ‘the Andrex plant’ (soft and strong for wiping the human body parts).The rosette stage is especially hairy, and the lower leaves of the ‘spire’ are more hairy than the upper ones. Also, the abaxial (lower) surface is more hairy than the adaxial. Macrophotography reveals the extent and nature of the trichomes (leaf hairs) that make this felt-like surface.
Hairiness of the leaf surface. Top-left: adaxial surface, top right: abaxial surface, lower image: abaxial surface at high magnification as might be seen with a x10 hand lens (see the branched and interlocking trichomes, and outlines of epidermal cells below). Images: Chris Jeffree.
The hairiness may also reduce the transpiration rate and reflect solar radiation, enabling the plant to tolerate sites that are dry (or with thin soil) and prone to full sunlight all day. I took the photograph below during rain. The water droplets lodge on the hairs and thus do not directly touch the leaf surface. This may explain why herbicides applied as a spray are ineffective unless a surfactant is added to reduce the surface tension of the droplet.
Abaxial surface of a leaf after rain. The droplets are trapped on the trichomes. Image: John Grace.
In Britain, its former use as a medicinal plant is recorded in Gerard’s Herbal of 1597. He has rather more to say about Great Mullein than for any other plant I’ve looked up:
Is it considered a useful medicinal plant even today? Much research has been done on the phytochemistry of this species, and many interesting and biologically-active compounds have been identified. It is used in traditional Chinese medicine but not in our evidence-based Western traditions, especially as it contains the toxic compound rotenone. Dried leaves or flowers can be purchased from health-food shops or on-line, although the most common use is for a kind of tea rather than medicine. On one internet site selling tea we are told:
“Flavour-wise, the mullein leaves produce a rich, aromatic flavour and is linked to a number of health benefits. Research has shown that it could reduce inflammation by helping muscles to relax – however more research is required before anything is for certain”.
The leaves can also be used as a ‘nicotine-free’ substitute for tobacco, and at least one company in the USA is marketing it, despite the total lack of evidence relating to the composition of combustion products.
Britain has 13 recognised species of Verbascum, but V. thapsus is by far the most common. Other fairly common species are V. nigrum, V. virgatum and V. pulverulentum. There are many hybrids (largely infertile) and numerous horticultural strains which vary in size, shape and flower colour, but all have the characteristic spire of flowers. The BSBI distribution map shows the species to be widespread in England and Wales, but avoiding western regions in Scotland and Ireland.
Verbascum thapsus, distribution in Britain and Ireland. From BSBI/maps.
How did it get its name? Gerard called it Tapsus barbatus but its modern name and accepted description was given by Linnaeus in 1753. Verbascum is probably a corrupted form of the Latin word barbascum meaning barbarian or bearded, referring to the plant’s hairiness. Thapsus probably comes from the Sicilian Isle of Thapsos where V. thapsus was gathered during ancient times or from the Tunisian island Thapsus. But the species name thapsus could also have been derived from the Greek word ‘thapsinos’ meaning yellow. Common names include: common mullein, candlewick, hedge-taper, lungwort, feltwort, blanketleaf, hare’s-beard, velvetplant, Jacob’s-, Jupiter’s- or Peter’s staff and old man’s flannel. Gerard called it Hag-Taper, supposedly thus-named because witches (hags) used it as a candle (taper).
References
Ansari S and Daehler CC. (2000). Common mullein (Verbascum thapsus): a literature review. Honolulu (HI): Pacific Cooperative Studies Unit, University of Hawaii at Manoa, Department of Botany. PCSU Technical Report, 127.
Averis B (2013) Plants and Habitats. Published by Ben Averis.
Braithwaite M (2015)The railway flora of Teviotdale revisited. Hawick Archaeological Society.
Clapham AR et al. (1987) Flora of the British Isles, 3rd Edition. Cambridge.
Gross KL and Werner PA (1978). The biology of Canadian weeds. 28. Verbascum thapsus L. and V. blattaria L. Canadian Journal of Plant Science 58, 401-413.
Odum S (1965). Germination of ancient seeds. Dansk Botanisk Arkiv 24: 70.
Wilhelm G (1974). The Mullein: plant piscicide of the mountain folk culture. Geographic – Review 64, 235-252.
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