Easily confused with : Hoary Mullein [but although that initially has white hairs on the leaves, they are easily shed. Also, Hoary Mullein is candelabra-branched, similar to the last photograph.]

Hybridizes with :

• Hungarian Mullein (Verbascum speciosum) [which has a branched main stem with flowers on all branches] to produce Verbascum × duernsteinense, which occurs in Cambridgeshire and Norfolk.
• Hoary Mullein (Verbascum pulverulentum) to produce Vebascum × godronii which occurs in Norfolk and may also be a garden escapee. This hybrid sheds the white hairs in patches to leave the leaves semi-shiny.
• White Mullein (Verbascum lychnitis) to produce Vebascum × thapsi which occurs with its parents in south and central Britain.

Uniquely identifiable characteristics

Distinguishing Feature :

ROTENONE Rotenone is found in the roots of Great Mullein, as well as in several other plants including Goat's-Rue, and in several non-native plants. It is a strong natural pesticide and insecticide that is used commercially as such, sometimes under the generic name Derris Powder which took its name from the non-native plant Tuba Plant (Derris elliptica) from which it was derived. It is a solid, obtained in powder form but used dissolved in water. It is also extremely toxic to fish when dissolved in water because it is absorbed directly into their blood stream via their gills, and is thus sometimes used as a piscicide; the fish float dead on the surface almost immediately. It was utilised this way by various indigenous tribes. Rotenone exerts its toxicity by interfering with electron transport in Mitochondria, the organelle within every cell of mammalian bodies and which is responsible for generating an energy supply for the cell in the form of Adenosine Triphosphate. It is relatively safe for humans and mammals because it is very poorly absorbed by the gastro-intestinal tract, but care should be taken for it has been linked to Parkinson's Disease. Deliberate ingestion can be fatal. Although its lifetime when exposed to sunlight is relatively short at less than a week, in water it can survive for 6 months, and its use near water courses is highly discouraged.

There are also a number of Triterpene Saponins in Mullein such as VerbascoSaponin, compare Cyclamin which also has an oxygen bridge on the steroidal component. The glycoside units are shown in blue. Also several Iridoid Glycosides such as Aucubin and Catalpol plus related compounds, and a few flavonoids which amount to 4% such as Rutin and Hesperidin. Hesperidin is found mainly in the skins of citrus fruits. It is a flavonone glycoside; the non-glycosidal component being the flavonone Hesperitin. Hesperidin is thought to contribute to the defence of the plant against pathogenic attack. It also acts as an anti-oxidant and can apparently cross the blood-brain barrier.