he thistle has been the national emblem of Scotland since the reign of Alexander III (1249–1286) and was used on silver coins issued by James III in 1470. It is the symbol of the Order of the Thistle, a high chivalric order of Scotland. It is found in many Scottish symbols and as the name of several Scottish football clubs. The thistle, crowned with the Scottish crown, was the symbol of seven of the eight former Scottish Police Services (from which a new national Police Service was formed in 2013), the sole exception being the former Northern Constabulary. The thistle is also the emblem of Encyclopædia Britannica, which originated in Edinburgh, Scotland.
It is also used to symbolise connection with Scotland overseas. For example, in Canada, it is one of the four floral emblems on the flag of Montreal; in the US, Carnegie Mellon University features the thistle in its crest in honour of the Scottish heritage of its founder, Andrew Carnegie.
According to a legend, an invading Norse army was attempting to sneak up at night upon a Scottish army's encampment. During this operation one barefoot Norseman had the misfortune to step upon a thistle, causing him to cry out in pain, thus alerting Scots to the presence of the Norse invaders. Some sources suggest the specific occasion was the Battle of Largs, which marked the beginning of the departure of King Haakon IV (Haakon the Elder) of Norway who, having control of the Northern Isles and Hebrides, had harried the coast of the Kingdom of Scotland for some years. Which species of thistle is referred to in the original legend is disputed. Popular modern usage favours cotton thistle (Onopordum acanthium), perhaps because of its more imposing appearance, though it is unlikely to have occurred in Scotland in mediaeval times; the spear thistle (Cirsium vulgare), an abundant native species in Scotland, is a more likely candidate. Other species, including dwarf thistle (Cirsium acaule), musk thistle (Carduus nutans), and melancholy thistle (Cirsium heterophyllum) have also been suggested.