Horsetail is found throughout the temperate climate zones of the Northern Hemisphere, including Asia, North America, and Europe. Seven of the twenty-five known species are British, the most common being Equisetum arvense. The Horsetails belong to a class of plants called ‘Equisetaceae’, and are similar to the fern family, germinating in the same way.
The epidermis contains so much silica that bunches of the stem have been sold for polishing metal and used to be imported from Holland for the purpose, hence the popular name of ‘dutch rushes’.
Primary chemical constituents of horsetail include flavonoids (15 different types), bitter principle, alkaloids (equisetin, nicotine, palustrine, palustrinine), silica, calcium, potassium, manganese, magnesium, sulphur, phytosterols, and tannin. Horsetail is rich in silicic acid and silicates, which provide approximately 2-3% elemental silicon.
The presence of the flavonoids and saponins are believed to have a diuretic effect, while the silicon content is thought to assist in strengthening connective tissue and provide anti-arthritic actions. Some experts have suggested the element silicon, present in horsetail, is also a vital component for bone and cartilage formation, making it beneficial in preventing osteoporosis.
Horsetail is believed to have been first recommended by the Roman physician Galen in ancient times, and it has been employed in various different cultures as a herbal remedy for problems such as arthritis, and kidney and bladder problems. Horsetail has been used for many years in both Chinese and European herbal medicine to treat external wounds - because of its high tannin content, Horsetail helps stop wounds bleeding, making it a popular treatment for nosebleeds and haemorrhoids.
In modern medicine, Horsetail is used to help alleviate painful urination, reduce inflammation of the prostate gland and for treating ulcers, particularly in the urinary passages. It is a diuretic and astringent, and has been found beneficial in treating kidney problems. The ashes of the plant are considered very valuable in normalising acidity of the stomach, and for dyspepsia.