The common nettle (Urtica dioica) is usually called the stinging nettle and I am sure we all discovered this plant at an early age the painful way! It has a fluid containing a histamine that 'irritates' should the hairs of the plant touch your skin. Despite this the plant has long been associated with herbal medicine and is linked to to a wide range of conditions for which it is considered a remedy. It is also used to make wine!
The common nettle is another of those dilemma plants. Where it grows it swamps everything else to form an expanse, almost a monoculture, and yet this is such an important plant for all sorts of insects, especially as the food plant for caterpillars of some butterfly and moth species. Some insects (the green nettle weavil for example) live only on this plant.
Common nettles grow just about anywhere where the soil is phosphate enriched which means that it tends to grow where there has been human interference in the soil, often near ex-human habitation. You can find it in hedgerows, waysides, woods, even damp areas such as fens. Although the plant is evident for most of the year its flowers appear from May to August.