Eriophorum angustifolium, commonly known as common cottongrass or common cottonsedge, is a species of flowering plant in the sedge family, Cyperaceae. Native to North America, North Asia, and Europe, it grows on peat or acidic soils, in open wetland, heath or moorland. It begins to flower in April or May and, after fertilisation in early summer, the small, unremarkable brown and green flowers develop distinctive white bristle-like seed-heads that resemble tufts of cotton; combined with its ecological suitability to bog, these characteristics give rise to the plant's alternative name, bog cotton.

In 2002 Plantlife conducted a "County Flowers" public survey to assign flowers to each of the counties of the United Kingdom and the Isle of Man. The results of this campaign designated a single plant species to a "county or metropolitan area" in the UK and Isle of Man. Some English counties already had flowers traditionally associated with them before 2002, and which were different from those assigned to them by Plantlife, including the white rose for Yorkshire, the poppy for Norfolk, and the cowslip for Essex. Some flowers were assigned to multiple counties.