This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Ubiquitous and common, the Nettle is also ancient, being found in Interglacial beds at Hoxne, Suffolk, and in Late Glacial beds also at the same place. It is found in the N. Temperate and Arctic regions in Europe, S. Africa, and the Andes. This is a ubiquitous species throughout Great Britain, and ranges as far north as the Shetlands, up to 2500 ft. in the Highlands.
The common Nettle is always to be found in a hedgerow, whether it be in fields and meadows or by the roadside. It is common in waste places, but it is erroneous to regard it as an indication of poor soil, for it requires simply an ordinary dry sandy loam, and where this sort of soil is exposed there it forms a clump, being a dominant species and excelling all other competitors.
The yellow fibrous roots of the Nettle are familiar to gardeners, and remarkable because of their interlacing habit. The habit is prostrate, then erect. The rootstock is creeping, and the plant is stoloniferous, with yellow, long, root fibres. The stem is downy, simple or branched, dark-green, protected by stinging hairs, which point forwards, each hair on a cushion of delicate tissue with an acid fluid, with a round head, situated obliquely, with easily fractured siliceous tissue just below the head. The point is directed forwards, and if seized from below the plant does not sting. The protoplasm in the stinging hairs is repelled by red light and attracted by blue. The leaves are egg-shaped to, forming a distinct association in a woodland habitat heart-shaped, lance-shaped, deeply toothed, the leaf-stalk long or short, with prominent impressed nerves. The stipules are linear to oblong.