Hoary Mullein, Verbascum pulverulentum. By UEA Playing Fields, Norwich, 5th July 2021.

One of Norwich’s local specialities is Hoary Mullein, Verbascum pulverulentum. It’s a spectacular plant and one I’m lucky to see every year. Nationally, it is mostly found in East Anglia and it is particularly abundant to the south and west of the city. The grounds of the University of East Anglia (UEA) are a good place to see it (note 1).

Hoary Mullein is thought to be a native plant (note 2) and it grows as a biennial or monocarpic perennial, producing its flowers once from its second year onwards, setting seed and dying. Flowers are produced from late June to August, usually peaking in July.

The spectacular flower spikes, which bear long side branches like a candelabra, can reach 1.5 – 2 metres (5 – 6.5 feet) tall. Individual flowers are pale yellow with whitish stamen hairs. The green parts of the plant are covered in a dense felt of white matted hairs, which gives the plants a frosted appearance. These hairs wear off and gather together to form distinctive balls of fluff.

Too late for that now: at the moment you’ll only find old seed heads or rosettes of the plant’s basal leaves. These are floppy and have a dense felt-like mat of hairs on the undersuface. They stay green all winter.

Basal rosettes of Hoary Mullein, Verbsacum pulverulentum. UEA, Norwich, 14th November 2022. (The yellow flower is a Dandelion.) This south-facing bank on well drained soil provides perfect growing conditions for Hoary Mullein.

Verbascum pulverulentum is a member of the Scrophulariaceae (Figwort family). There are around a dozen species of Verbascum growing wild in the British Isles and plants hybridise readily (note 3), which can make identification rather tricky.

The Flora of East Anglia and Wild Flower Finder websites have some great photos of Hoary Mullein.

Mulleins make good garden plants. They prefer light soils and a sunny spot. Plants produce a long tap root and cope well with droughts. There are tips on which species to grow and how to grow them on the Gardeners’ World, Gardens Illustrated and Garden Design Journal websites.

One of my favourite garden Verbascums is Verbascum chaixii ‘Album’, which has white flowers with red-purple centres. Our back garden is a bit too shady in winter for Verbascums to thrive but I grow a couple of species on the light sandy soil on my allotment: Great Mullein (Verbascum thapsus) and Dark Mullein (Verbascum nigrum). The former can grow as tall as Verbascum pulverulentum but the flower spikes don’t branch. The latter behaved as a short-lived perennial for me, flowering several years in a row, though it is supposed to be a biennial. This year I had a spectacular self-sown plant with flowers like Dark Mullein and a growth habit more like Great Mullein, presumably a hybrid.

Mulleins don’t make good eating and the Plants for a Future website lists no known edible uses for Verbascum pulverulentum. It also warns that those fluffy hairs can act as an irritant. The plant contains a rich mixture of compounds (note 4). Two of these, listed by the Plants for a Future website, are coumarin and also rotenone (note 5). The latter has been used as an insecticide and fish poison (note 6).

One insect that thrives on Verbascum leaves is the Mullein Moth. I’ve never seen the moth, which flies in April and May, but the beautiful caterpillars are a common sight in early summer in the south of England, including Norfolk. They also feed on Buddleja leaves. They can strip whole Verbascum plants but usually (in my experience) the plants usually survive, flower and set seed (note 7).

The very hungry caterpillar: Mullein Moth, Cucullia verbasci.

The name Verbascum is a corruption of the Latin adjective barbascum, which means “with a beard”, a reference to these plants’ hairy leaves.

The origin of the English name is less clear. “Mullein” may come from a word for yellow, but another explanation is that it is a corruption of the Latin “mollis” meaning soft. It is usually pronounced “mullen”.

On a related note, one of the American names for Great Mullein (Verbascum thapsus) is “cowboy toilet paper“, presumably a reference to the soft, strong (and rather long) leaves.

Notes

Note 1 – “By the A14 near Bury St. Edmunds” in Suffolk is apparently another good place to see it. “A Flora of Norfolk” mentions the shingle bank between Snettisham and Heacham as another hot spot. (Gillian Beckett, Alec Bull and Robin Stevenson, “A Flora of Norfolk”.  Privately published, 1999).

Outside the British Isles, Verbascum pulverulentum is native elsewhere in Europe (Albania, Belgium, Bulgaria, Corse, France, Germany, Great Britain, Greece, Hungary, Italy, Portugal, Romania, Sardegna, Sicilia, Spain, Switzerland and the former Yugoslavia) and has been introduced into Austria and Madeira and the United States (Washington state).

Note 2 – Stace (note 3) says Verbascum pulverulentum is “probably native” on chalky soils in East Anglia and a casual or naturalised escape elsewhere. The Flora of East Anglia website says it is “of uncertain origin, perhaps native”.

Note 3 – Clive Stace, “New Flora of the British Isles“, Fourth Edition, 2019. Verbascum species are listed on pages 639 – 642.

Note 4 – Blanco-Salas et. al. (2021) have looked into the phytochemistry of Verbascum plants in relation to their use in Spanish folk medicine. The results can be found in “Searching for Scientific Explanations for the Uses of Spanish Folk Medicine: A Review on the Case of Mullein (Verbascum, Scrophulariaceae)“, Biology Vol. 10 p618.

Note 5 – The Plants for a Future website notes that the quantities are not given.

Note 6 – I remember using “Derris dust” as a garden insecticide back in the late 1970s; its active ingredient was rotenone. You could still buy it in the UK until around 2009.

Even if it was still available I wouldn’t use it. Although rotenone degrades quite quickly, it is completely indiscriminate in its action and will kill other arthropods as well as the “pest” being targeted. There are also links between its usage and Parkinson’s disease.

I’ve only just realised, in researching this blog post, that Derris is a genus of leguminous plant (family Fabaceae). Species of Derris include the Tuba plant (Derris elliptica) and Jewel Vine (Derris involuta), whose roots were used to make the powder.