Petasites hybridus

Daisy & Dandelion Family [Asteraceae]

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Pappus: pappusZpossible (white)
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31st March 2008, Daisy Nook, Greater Manchester. Photo: © RWD
Spreading in a low moist mossy valley. Probably male plants?

27th April 2005, Skipton, Leeds & Liverpool canal. Photo: © RWD
Somewhat more mature plants, taller flowers, much larger leaves. Probably female plants?

31st March 2008, Daisy Nook, Greater Manchester. Photo: © RWD
Young plants with very few and small leaves. Flower spike compact.

1st March 2008, Lathkilldale, Derbyshire. Photo: © RWD
Almost all parts are bright red to maroon at first. A flowering spike emerges from the centre of a sheath of bracts with Small leaves on the ends.

16th April 2009, River Ribble, Great Mitton. Photo: © RWD
Flower bunches spreading out. Leaves, cardioid-shaped with slight teeth on the edges are getting larger.

8th April 2010, Longdendale Valley Trail, Glossop, Derbys. Photo: © RWD
 Newly 'hatched' specimens have bright-red strap-shaped bracts and sheaths around the flower bunches. The stems are thick at first and covered in white woolly hairs.

8th April 2010, Longdendale Valley Trail, Glossop, Derbys. Photo: © RWD
 Each female floret has a ring of white styles around the central part. Male and female flowers are on separate plants. Here female, which has flower clusters that hardly open, are smaller but the plant is overall taller than the male plants.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 Reddish stems bearing numerous short narrow purplish bracts and short stalks with a single compound flower on the end. The numerous stigmas are like miniature shaving brushes, each with a T-shaped style at the end.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 The compound flowers can at times look similar to shaving brushes.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 These compound flowers seem to have but one central five-petalled flower, which have a central but sterile stamen.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 The flower head is cupped by numerous light-green sepals, the flower stem has many very shorter and narrower purple bracts.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 The plants have few leaves, these are oval-cardioid shaped.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 A mixture of the cardioid leaves and oval-cardioid ones with a slight point on the furthest extremity. Prominent lighter-coloured lilac veins.

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
 The stems have a whitish-pink fibrous appearance.

8th April 2010, Longdendale Valley Trail, Glossop, Derbys. Photo: © RWD
 Each individual flower has five pink but white-tipped flowers. The central flowers are yet to open in each bunch. The pollen is white.

3rd April 2009, Kens Boat Crawl, Lancaster Canal. Photo: © RWD
  The single stamen is at first enclosed by a long barrel-shaped covering with five deep-red stripes reminiscent of sweets. Or could these be sterile female flowers which are sometimes present (or even male sterile flowers).

3rd April 2009, Kens Boat Crawl, Lancaster Canal. Photo: © RWD
  The above specimen from a differing viewpoint, the single stamen yet to burst through the striped covering..

29th April 2006, Hest Bank, Lancaster Canal. Photo: © RWD
 Male. Losing their immature redness, and becoming green. Male plants have more than one flower in each bunch (females have but one seemingly sterile male at the centre surrounded by dozens of white styles). Almost all the flowers in each bunch have now opened.

12th Feb 2008, near Hen Cloud, Derbyshire. Photo: © RWD
 The thick stems, now mostly devoid of woolly hairs, take on a fibrous appearance.

8th April 2010, Longdendale Valley Trail, Glossop, Derbys. Photo: © RWD
 Purple striations on the 'tube' from which the stamen protrudes.

11th April 2010, River Bollin, Quarry Bank Mill, Gtr M/cr. Photo: © RWD
 The male plants have white stamens with a single sterile clavate (club-shaped) stigma. The sex of Butterbur florets is complex, some florets seemingly being composed of sterile bits of the opposite sex.

23rd May 2010, Rufford Branch Canal, Lancs. Photo: © RWD
 Gone to seed. Like most flowers of the Dandelion Family, the seeds are on long white hairs arranged on a pappus.

18th May 2012, River Brock, The Fylde, Lancs. Photo: © Richard Davies
 A magnificent specimen un-ravaged by wind or rain.

18th May 2012, River Brock, The Fylde, Lancs. Photo: © Richard Davies
 Each seed has its own 'parachute' of white hairs. The white 'seed-clocks' ready to be dispersed by the wind. Un-like Dandelion, the seeds are attached directly to the parachute, without an intervening long stick.

18th May 2012, River Brock, The Fylde, Lancs. Photo: © Richard Davies
 The seeds are brown, long, grooved but otherwise smooth and without nodules.

20th June 2007, Huddersfield Narrow Canal, Diggle. Photo: © RWD
Older specimens lose all their flowers and the leaves grow enormously, up to 2 feet across.

24th June 2007, Peak Forest Canal, Strines. Photo: © RWD
On long stalks up to four feet high. Looking very similar to Rhubarb.

2nd May 2008, Daisy Nook, Gtr M/cr. Photo: © RWD
The large leaves have prominent supporting ribs or veins underneath. The underside is of a lighter green.

12th June 2008, Wye Dale, Derbyshire. Photo: © RWD
The stalks are very stout (photo shows the leaves joining the stalks from underneath)

13th April 2009, Sett Valley Trail, New Mills. Photo: © RWD
These leaves seem of a different shape to those of normal Butterbur, although of similar cardioid outline, they are longer, and some have a distinctive arrow-head shape.

Not to be confused with : Bur-Marigold, Butterwort or Burdock [plants of similar name]

When of advanced age, the leaves resemble and are of similar size to those of : Chilean Giant-Rhubarb (Gunnera tinctoria), Brazilian Giant-Rhubarb (Gunnera manicata), Indian-Rhubarb (Darmera peltata), and Rhubarb (Rheum rhubarbarum).

Some similarities to : White Butterbur but that has reduced-width leaves which are more arrow-shaped, and all white flowers. The leaves of Colt's-foot are also similar, but usually smaller, and the marginal teeth on Colt's-foot leaves are shorter in relation to their width, and are also stained reddish when viewed in sunlight.

Slight resemblance to : Winter Heliotrope but that has much smaller and smoother leaves which are evergreen (and thus there all year around unlike Butterbur where the flowers appear before the leaves) and a more open and shorter flower head spike.

Superficial resemblance to : Giant Butterbur but that has much larger and white outer disc florets and yellow inner disc florets; and when young looks like a giant cauliflower.

Uniquely identifiable characteristics

Distinguishing Feature :

Butterbur grows in marshy or damp soil, besides streams and canals, within moist forests or amongst mosses on the ground. The flowers are the first to appear, followed by leaves which get bigger and bigger until when the flower is spent the leaves have grown up to 2 feet across on long stalks up to 3 feet high.

The enormous leaves of Butterbur were once used to wrap butter, hence the name 'Butterbur'. Butterbur is dioecious, meaning it bears male and female flowers on separate plants. The male plant occurring throughout the UK, but the female plant occurring predominantly in the North and Central UK.

The flowers of the male plant are larger (7-12mm) than those of the female plant (3-6mm), but the situation is reverse regarding the height of the plants; the females are taller. It is likely that it is only native where both sexes occur together.

Its botanical name is Petasites hybridus because it only looked as though it was a hybrid of two different plants - so the person who named it added the specific epithet 'hybridum' to signify that. If it really was a hybrid, then the botanical name would include a '×' between the genus name and the specific epithet. The fact that this '×' is omitted indicates that it only looked like a hybrid.


Dodecanal (aka Lauraldehyde) is contained in the sap and released into the atmosphere from broken stems of Butterbur where it then smells of fresh laundry.


Reflecting the structure of the Sesquiterpenoids detailed below are two ketone sesquiterpenes found in the essential oil of Butterbur, Nooketone and Dihydro Karanone. There are others not shown here.

Nookatone is also present in Grapefruits, from which it can be extracted commercially, for it is an expensive aromatic compound used as a fragrance. It is an effective repellent against termites and the sheep ticks that may carry Lyme disease. Ingested, a dose of nootaketone daily stimulates energy metabolism, reducing the significance of a high-fat or high-sugar diet, thus helping stem development of hyperglycaemia. Its non-ketonic analogue is called Valencene which is contained within Valencia Oranges.

Dihydro Karanone has a strongly woody, slightly citrus-like fragrance, and indeed it is also found in several Agarwoods.


Other compounds present are the sesquiterpenoid glycoside isoPetasoside and its aglycone (without the attached sugar molecule) the phytotoxin sesquiterpenoid isoPetasol. Petasol and isoPetasol are potentially of use as herbicides. The only difference between Petasol and isoPetasol is the position of the double bond on the side chain. A similar difference applies to the Petasin and isoPetasin (shown below) which are esters of the above sesquiterpenoids. All occur in Butterbur, and from which they all derive their names.

Petasin and isoPetasin are the main active constituents of Butterbur, but at least 20 other sesquiterpene esters have been identified. The two are double-bond isomers of each other (top right). (There are many differing stereoisomers of these compounds present in Butterbur, too many to detail, and they all have the same chemical formula as those above anyway if not the spatial arrangement. Both Petasin and isoPetasin have pharmacological properties and are effective against migraine. Petasin can also be used to treat allergies.

Two sulfur-substituted Petasins were also discovered in Butterbur, S-Petasin and iso-S-Petasin.


Two Furano-sesquiterpenoids (or more strictly Furano-Eremophilanes) echo the structures of the Petasols, but are more poisonous on account of the fused furan ring (the five-membered heterocyclic ring with an embedded oxygen atom) which is easily broken.

An Eremophilane Lactone found in Butterbur. Notice the similarity to the two Furano-Eromophilanes above, but with the major difference being that the ring oxygen has been replaced by a nitrogen atom, meaning that this one is an alkaloid.


The major Pyrrolizidine Alkaloids (PAs) account for 90% of the total alkaloid content of Butterbur. These PA's have the 1,2-unsaturated Necine structure. The main ones being Senecionine, Integerrimine and Senkirkine.

The Toxicity of Pyrrolizidines

Most, but not all, Pyrrolizidine alkaloids are hepatotoxic, damaging the liver if ingested in sufficient quantities. PAs themselves show little or no toxicity, it is only in the mammalian liver where they are metabolized to highly toxic alkylating pyrrols but only if their structure includes a double-bond in the 1,2-position of the necine and also has a substituted group on the Nitrogen atom and esterification of the OH-groups of the necine (with mono-esters being less toxic than di-esters). Accordingly, the structure of Tussilagine shows that it is not hepatotoxic.

Tussilagine is a very simple Pyrrolizidine Alkaloid which was discovered in Colt's-foot (Tussilago farfara), hence the name. Tussilagine is one of the few pyrrolizidine alkaloids that are not toxic and does not cause chromosome damage in cultured human lymphocytes.

Integerrimine has a 12-membered di-lactonic pyrrolizidine ring and is pyrrolizidine alkaloid of the retronecine type III kind. It is found in various other plants belonging to the Senecio and many other Genera. It is a geometric isomer of Senecionine, shown below. Integerrimine is anti-mitotic, inhibiting cell division, and induces abortions and fetal malformations in mice. Although it does not induce germ-cell line chromosomal aberrations , it does alter the soma-cell line chromosomes in bone marrow cells.

Senecionine (aka Aureine and Squalidine) is a pyrrolizidine alkaloid which is hepatotoxic, damaging the liver on ingestion, and found in Tansy and also in species of Senecio [in the Daisy Family] (which includes Ragworts such as Oxford Ragwort, Groundsels) and species of Crotalaria (a member of the Pea Family) which grows in the tropics. Senecionine has uses in the biological laboratory.

Both Senkirkine and Petasitenine lack the bridging bond across the N-decahedron, thus failing to making them into two fused pentahedra. Senkirkine, which can induce hepatic tumours in rats, also occurs in Colt's-foot.

Petasitenine (below), which was discovered in Butterbur, has an un-stable energetic epoxy group (top left). Compare this structure with that of Jacobine, another pyrrolizidine alkaloid. Petasitenine is also present in Giant Butterbur (Petasites japonicus). Tussilagine (and its stereoisomer isoTussilagine) are both also found in Arnica species flowers.

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Petasites hybridus

Daisy & Dandelion Family [Asteraceae]

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