Claywort, coughwort, foal
Tussilago farfara L
Perennial Broad-leaved Weeds
Coltsfoot is a widespread, native, rhizomatous perennial that occurs on all but the more acid soils. It can be especially troublesome on heavy land. Lime also appears to favour it. Coltsfoot is common on disturbed ground in many habitats including arable fields and wasteland. It can be a problem weed in gardens.
Coltsfoot has many medicinal and therapeutic uses including as a cough remedy. The leaves contain unusually high levels of sodium, calcium and magnesium.
Flowering and seed production usually occur before the leaves emerge. In southern Britain flowering occurs in March-April but in the north, lower temperatures may delay flowering. The flowers are insect or self-pollinated. Seeds arise in the outer ray florets of the flower heads, rarely in the inner disk florets. The mean number of seeds per flower head is 157. Seed number per plant is around 1,500 to 3,500. By April-June the seeds are ripe and dispersal takes place.
Coltsfoot seed is not dormant and does not require light for germination but germination is slower in shade. It germinates soon after shedding, usually on the soil surface, but seedling losses are high due to fluctuating moisture levels. Seedlings initially form a taproot but after 6 weeks a strong adventitious root system arises from the stem. Soon after this rhizomes are initiated. The adventitious roots are strongly contractile and pull the shoot down into the soil and the rhizomes develop from the buried axillary buds. The rhizomes grow extensively after initiation and have been traced over 1 m down in heavy clay. In the autumn, flower buds are initiated and the leaves die off. The flower buds develop through January and with rising temperatures in early spring the flower stems elongate and flowering commences. The shoot then dies leaving the rhizomes that were formed the previous year. These produce leafy aerial shoots and the cycle continues. The shoot is therefore monocarpic.
Persistence and Spread
Seed remains viable for just 2-3 months under natural conditions, sometimes less if buried in soil where fatal germination may occur.
The plumed seed is wind dispersed and can travel over 4 km. Laboratory tests suggest maximum dispersal distances of 3 and 4.4 metres at wind speeds of 10.9 and 16.4 km/hour respectively but this would be affected by plant height.
Vegetative reproduction is by thick fleshy rhizomes that can penetrate several feet into the soil. Fragments of the rhizomes can readily produce new shoots. The larger the fragment the more likely it is to regenerate. Fragments can emerge from burial at 60 cm deep. New rhizomes do not seem to invade soil containing the residues of old rhizomes.
It is important to prevent seeding and flowers should be hoed off. The leaves should be removed to exhaust the rhizomes. The rhizomes are susceptible to drying and in hot weather, ploughing or cultivation that exposes the rhizome will help to destroy it. In an arable rotation, a single shallow stubble cultivation after cereal harvest followed by deep ploughing later in the autumn helps to contain a coltsfoot population. Summer fallowing may also be effective in reducing the weed. Nutrient reserves are lowest in summer.
In light soils, frequent cultivation can reduce the weed and a dense crop stand will out-compete it. Smother crops of mustard or vetches will help to suppress coltsfoot. Laying the land down to permanent pasture destroys it. Coltsfoot is vulnerable to grazing, mowing and trampling.
Birds may take the whole flower head along with the seeds. Slugs have also been seen to attack the flowers. Swift moth larvae, cockchafers and wireworms feed on the underground stems.
Updated October 2007.