Tussilago farfara L., Colt's-foot

Account Summary

Growth form and preferred habitats

Colt's-foot is a very common and widespread, low-growing, patch-forming perennial with a stout rootstock and vigorous horizontally spreading underground rhizomes. It colonises both moist and dry, open, natural habitats such as stream banks, damp slopes, hillside flushes, coastal dunes, shingle, screes and unstable steep slopes. It also frequents artificial, man-made, disturbed ground, such as along roadside verges and hedgebanks, in rough grasslands, old quarries, railtrack ballast and railway cuttings, waste ground, gravel paths and neglected areas in gardens where it can become a very persistent weed (Garrard & Streeter 1983; Sinker et al. 1985; Grime et al. 1988, 2007). It is a pioneer coloniser of a wide range of bare or disturbed open habitats on soils varying from heavy clay to silt and from sand to gravel and shingle. In terms of moisture, it ranges from poorly drained clay with a high winter water table, to dry stony or sandy conditions, from moderately acid to calcareous and from nutrient poor to medium or fertile soils. It is scarce or absent from acidic soils below pH 4.5 and can only tolerate light shade (Grime et al. 1988, 2007).

The long-lived, but low canopy shade T. farfara provides means that it can dominate short turf vegetation, but is unable to compete with taller plants in fertile soils and it tends to be steadily outgrown and replaced. In less fertile, more compacted, or heavy clayey soils, Colt's-foot is able to persist for very many years.

In late autumn, the leaves eventually die back, but if the plant is growing in agricultural grassland the leaf longevity results in Colt's-foot being adversely affected by regular grazing, mowing or heavy trampling (Grime et al. 1988, 2007).

The established strategy of T. farfara is categorised as C/CR, meaning it is intermediate between a Competitor and a Competitive Ruderal (Grime et al. 1988, 2007).

Fermanagh occurrence

In Fermanagh, T. farfara is a very common and widespread ruderal weed, being recorded in 324 tetrads, 61.4% of those in the VC.

Flowering reproduction

The scaly but leafless, hollow flowering stems appear early in the season – in Fermanagh from February onwards, reaching a peak in late March, extending into May as a secondary flush of blooming takes place on ground with more fertile soil. The solitary pale- or golden-yellow flowerheads, 25-30 mm diameter, are terminal on whitish, buff or purplish, scaly or bracteate, woolly stems up to 20 cm tall, which frequently are formed in clusters of six to eight or many more (Clapham et al. 1962; Salisbury 1964).

The leaves are all basal and they emerge about a month after the flowers emerge. The plants do not tend to form the very large, conspicuous patches in the way that Petasites fragrans (Winter Heliotrope) does in wayside situations – another large-leaved species that flowers during in the winter months. The extensive branching rhizome of T. farfara nevertheless produces many short shoots, each of which directly gives rise to a rosette of five to seven leaves after or around the middle of the flowering period. The leaves are distinctive, deeply cordate at their base, generally 10-20 cm in diameter (about the size of a colt's foot), but occasionally very large, up to 30 cm across, broadly heart- or shield-shaped, yellowish-green, very shallowly five- to twelve-lobed.

The upper leaf surface is at first cobwebbed with white caducous hairs that are gradually shed over the following weeks. The lower leaf surface is coated with a thicker felt of cottony white hairs and the margins are regularly, though distantly and acutely toothed. The upper surfaces of the teeth and of the slender leafstalk are generally a deep purple colour. The leaves once produced and expanded persist through summer and early autumn, dying down and the plant disappearing underground in late autumn (usually October).

Colt's-foot flowerheads are surrounded by about 20 reddish involucral bracts (phyllaries) in one or two rows. They contain a central group of 20-40 tubular, male florets, surrounded by between 200-300 female, strap-shaped (ligulate) florets. The flowerheads close up at night or in cold, dark weather, but open up again in warm sunshine, taking about 90 minutes to do so (Garrard & Streeter 1983). The mature flowerheads are held erect and are visited by flies and early flying bees for nectar and pollen produced only by the inner cluster of male flowers. Should insect pollination fail, the flowers can self-pollinate due to the closing of the heads at night and in cold weather (Hutchinson 1972).

After fertilisation, the head first withers and droops. The stem carrying the head then lengthens to around 30 cm, and when the fruits are ripe and ready for dispersal in April or early May, it straightens up again to release the very many wind-borne achenes, each equipped with its snowy white pappus parachute. The achenes are 5-10 mm long, cylindrical, slightly curved (like a miniature banana), brown, five-ribbed and glabrous (Butcher 1961). The attached pappus is 10-14 mm long, about twice the length of the achene. It is composed of many rows of silky, white, simple hairs so that the flowerhead looks like a ball of white fluff (Melderis & Bangerter 1955; Sell & Murrell 2006).

Despite the large number of female florets, measurements of achene germination suggest that each flowerhead produces an average of around 140 viable seeds (ie achenes) (Salisbury 1964). Seed is short-lived and measurements under natural conditions found that over 50% of were non-viable after just two months (Bakker 1960). The survey of soil seed banks in NW Europe contains ten estimates of seed survival, all but one of them regarding it as transient (Thompson et al. 1997). Germination of freshly shed seed in open conditions is rapid in April and May (Ogden 1974), but seedlings are not often observed and their mortality is probably high, since continuously moist conditions are essential for their establishment (Salisbury 1964).

Vegetative reproduction and spread

Although it is often difficult to be certain, observed growth rates suggest that substantial patches of Colt's-foot may well consist of a single clonal individual due to the vigour, frequent branching and lateral spread of the underground rhizome. The rhizome is short-lived, but when it dies back, it releases isolated daughter plants as leaf-rosettes (Grime et al. 1988, 2007). As any gardener who has tried to remove or control it will confirm, excavation of the rhizome is extremely difficult, since it is fragile and breaks easily, can run at several different depths and may penetrate to 60 cm or deeper. Rhizome fragments appear to be capable of survival deep in the soil in a long-term dormant manner (Grieve 1931).

Established colonies can spread their rhizomes radially by up to 100 cm per year (Bakker 1960; Salisbury 1964). Man undoubtedly assists the species dispersal by transfer of rhizome fragments during soil disturbance.

Fossil history

The fossil record is meagre, consisting of fruits (ie achenes) from the early Cromer Forest Bed series and again from sub-stage IV of the Ipswichian interglacial. Godwin (1975) comments that, "the present range and ecological habit allow one to anticipate records from Weichselian deposits in the future". By this, the current author (RSF) takes it that given time and further research effort by palynologists and palaeontologists, more fossils are expected from later, more recent sediments continuing the record of Colt's-foot closer to the present day.

British and Irish occurrence

The success of the plant in colonising bare mineral soil and persisting is reflected both in its high frequency at the hectad level of discrimination and very widespread distribution throughout B & I. It occurs from sea-level to an altitude of 1,065 m in the Breadalbanes, Mid-Perthshire (VC 88). The only areas where it is less prevalent are in the SW of Ireland and in Shetland, where it is an introduced alien. There have been losses in areas where arable agriculture takes place, since intensive farming methods, including herbicides, have eliminated the species (H.J. Killick, in: Stroh et al. 2023).

European and world occurrence

T. farfara belongs to the Eurosiberian boreo-temperate phytogeographical element. In Europe, it extends from the N Iberian Peninsula northwards to 71^oN in Norway and is introduced in Iceland. It also extends eastwards into N & W Asia. It is also present in NW Africa and has been accidently introduced and become quite widely naturalised in eastern N America (Hultén & Fries 1986, Map 1828; Sell & Murrell 2006). It is also introduced in South Island, New Zealand, where it is rare but well established in a few localities (Webb et al. 1988).

Names

The botanical name 'Tussilago' is derived from a combination of the Latin 'tussis', meaning 'a cough', plus the feminine suffix '-ago' meaning 'to act on', a reference to one of its medicinal uses (Gilbert-Carter 1964). There are several possibilities floated for the origin of the Latin specific epithet 'farfara'. One is that it derived from an old generic name for Butterbur, Petasites fragrans, a plant which is often mistaken for T. farfara (Gledhill 1985). A second suggestion is that it is derived from 'Farfarus', an ancient name used by the Roman writer, Pliny, perhaps for White Poplar, Populus alba, the leaves of which resemble in shape and hairiness those of Colt's-foot, to some extent at least (Melderis & Bangerter 1955). A third possibility arises from the fact that Farfara Gilib. was a previous name for the genus Tussilago L. and perhaps was simply retained for use as the specific epithet (Willis 1973).

T. farfara has many English common names, Grigson (1955, 1987) for example listing 29. A high proportion of the names link animal's feet to the leaf shape, 'Colt's-foot' itself being derived from a translation of the medieval Latin name 'pes pulli', meaning 'foal's foot' (Grigson 1974). Other animal names include 'Bull's Foot', 'Ass' Foot', 'Hoofs', 'Horse-hoof', 'Sow-foot'. 'Son afore the father' is a Scottish and Cumbrian name, the reference being to the flower appearing before the leaf. The large leaf size is noted by 'Wild Rhubarb' and 'Hogweed' and the yellow flowers by 'Yellow Stars' and 'Yellow Trumpets' (Grigson 1955, 1987).

Medicinal and other uses

Other common names refer to the medicinal uses of the plant, which are primarily as a cough dispeller. Allen & Hatfield (2004) refer to it as, "the age-old folk cure for coughs par excellence". The smoking of the leaves to relieve a cough was recommended by herbalists from Dioscorides onwards to the present (Vickery 1995) and they are the principal ingredient in British Herbal Tobacco, used to treat asthma, catarrh, bronchitis and other lung and chest complaints. A decoction of the leaves boiled down in water and sweetened with honey is also taken for colds and asthma (Grieve 1931). Colt's-foot leaves and flowerstalks as a demulcent against coughs were recommended in the British Pharmaceutical Codex of 1949 for the preparation of Syrup of Colt's-foot, regarded as a suitable remedy for chronic bronchitis (Grieve 1931; Grigson 1955, 1987). A tincture of Colt's-foot is currently used in homoeopathic medicine for relieving neuralgia (Le Strange 1977). The plant has also been used as a blood purifier and it was an ingredient of an ointment used to treat, "sprains and all swellings of the joints", in parts of Scotland and in N Ireland (Allen & Hatfield 2004).

Tussilago farara plants have been put to unexpected use, past and present. The young leaves of T. farfara are covered on both surfaces with woolly hairs, those on the upper surface being caducous (ie dropping early), rubbing off naturally with any type of friction as the leaf expands. In the days before safety matches, the down from these leaves was collected and transformed into tinder by being wrapped in a rag, dipped in saltpetre and dried in the sun (Grieve 1931). For reasons the current author (RSF) cannot fathom, a tincture of T. farfara is an ingredient of modern commercial hairsprays (Mabberley 1997).

Toxicity

Tussilago farfara contains the pyrrolizidine alkaloids Senecionine and Senkirkine that can cause severe liver damage and cancerous tumour development. Gardeners and other outdoor workers handling the plant are advised to wear gloves and wash hands carefully after contact with it.

Threats

None.

References

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