Stinging nettle or common nettle, Urtica dioica, is a herbaceous perennial flowering plant, native to Europe, Asia, northern Africa, and North America, and is the best-known member of the nettle genus Urtica. Stinging nettle is a dioecious herbaceous perennial, 1 to 2 m (3 to 7 ft) tall in the summer and dying down to the ground in winter. It has widely spreading rhizomes and stolons, and these, like the roots, are bright yellow. The soft green leaves are 3 to 15 cm (1 to 6 in) long and are borne oppositely on an erect wiry green stem. The leaves have a strongly serrated margin, a cordate base and an acuminate tip with a terminal leaf tooth longer than adjacent laterals. It bears small greenish or brownish 4-merous flowers in dense axillary inflorescences. The leaves and stems are very hairy with non-stinging hairs and also bear many stinging hairs (trichomes), whose tips come off when touched, transforming the hair into a needle that will inject several chemicals: acetylcholine, histamine, 5-HT or serotonin, and possibly formic acid. This mixture of chemical compounds cause a sting or paresthesia from which the species derives its common name, as well as the colloquial names burn nettle, burn weed, burn hazel. This sting can last from only a few minutes to as long as a week. Stinging Nettle has a flavour similar to spinach when cooked, and is rich in vitamins A, C, D, iron, potassium, manganese, and calcium. Young plants were harvested by Native Americans and used as a cooked plant in spring when other food plants were scarce. A soup made from the young shoots is considered a spring delicacy in Denmark and Sweden. Cooking or drying completely neutralizes the toxic components found in this plant. After Stinging Nettle enters its flowering and seed setting stages the leaves develop gritty particles called "cystoliths", which can irritate the urinary tract.  Soaking nettles in water will remove the stinging chemicals from the plant, which allows them to be handled and eaten without incidence of stinging. Young leaves generally have a better taste than older, more bitter leaves. Nettles can be used in a variety of recipes, such as polenta and pesto. Nettle soup (or "BrÃ¦ndnÃ¦ldesuppe" in Danish, "NÃ¤sselsoppa" in Swedish and "Nokkoskeitto" in Finnish) is a common use of the plant, particularly in Northern Europe. Young nettle leaves are similar in texture to spinach and other leafy greens, and can be substituted for or mixed with other greens in recipes. Nettles are sometimes used in cheese making, for example in the production of Yarg and as a flavouring in varieties of Gouda Unusually for a leafy green vegetable stinging nettle also contains high levels of protein; 40%. Cooking, crushing or chopping disables the stinging hairs. Stinging nettle leaves are high in nutrients, and the leaves can be mixed with other ingredients to create a soup rich in calcium and iron. Nettle soup is a good source of nutrients for people who lack meat or fruit in their diets. The young leaves are edible and make a very good pot-herb. The leaves are also dried and may then be used to make a tisane, as can also be done with the nettle's flowers. In the UK, an annual Stinging Nettle Eating Championship draws thousands of people to Dorset, where competitors attempt to eat as much of the raw plant as possible. Competitors are given 60 cm (20 in) stalks of the plant, from which they strip the leaves and eat them. Whoever strips and eats the most stinging nettle leaves in a fixed time is the winner. The competition dates back to 1986, when two neighbouring farmers attempted to settle a dispute about who was responsible for controlling the weed.