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Coltsfoot is either a useful medicinal plant or an invasive weed, depending on the circumstances. It is a small plant in the aster family, known as Tussilago farfara. Its common name is derived from its leaves. They resemble a colt’s foot, cut cross-wise. The use of this herb is controversial, since it contains low concentrations of carcinogenic toxins that are thought to accumulate in the liver.
This small plant grows to between 4 and 12 in (10 to 30 cm) in height. The coltsfoot flower is yellow and composite, resembling that of a dandelion. It is the sole flower produced on a stem. This flower is produced early in the spring, before dandelions typically bloom. It produces seeds and dies back before the coltsfoot leaves are produced.
A perennial herb, it is very effective at colonizing disturbed areas and can form large clumps of plants. It prefers moist areas, such as ditches, fields, and stream banks, but will grow along roadsides. The plants spread by both rhizomes and seeds. Also, the roots can survive long periods of being deeply buried. So later, when the soil is disturbed, there can suddenly be an invasion of coltsfoot plants in areas where they had not previously been observed.
While native to Europe and Asia, this plant is now endemic to North and South America. It is thought to have been introduced by settlers, for medicinal purposes. In North America, it usually grows in southern Canada and the north-central and northeastern United States. It is considered an invasive weed in some areas, and can be very difficult to control in fields and gardens.
The genus name of this plant, Tussilago, comes from the Latin for tussis, which means 'cough.' It is an old folk remedy for treating coughs. The leaves, flowers, and roots are generally harvested and sold separately. Use as a tea is one way in which this herb is utilized as a cough suppressant. There are a number of mixtures of these teas available for sale in Europe.
The herb is also sometimes smoked to treat asthma. Coltsfoot extract can also be prepared as a syrup, which is recommended for dry coughs. Another use is as a substitute for tobacco.
One problem with using this herb medicinally is that the leaves and flowers have been found to contain toxic compounds known as pyrrolizidine alkaloids. These are found in low concentrations in the plants, but are thought to accumulate in the liver over time. In high concentrations, they have been found to cause cancer in rats. Germany had banned the sale of coltsfoot, but varieties are now available that do not contain these alkaloids.
Some people feel that the health risks are low and the benefits are great enough to warrant the use of coltsfoot. One should not take it for a long period of time, however. It is imperative that pregnant women not take varieties of this herb containing the alkaloids. There have been instances of infants developing severe liver disease because their mothers drank coltsfoot tea during pregnancy.