There are around 20 species of thistle in the UK with the three most common in our area probably being the creeping thistle, marsh thistle and spear thistle but many others do occur including the welted thistle and melancholy thistle.
Some like the creeping are named after their method of spreading, the marsh from its habitat and the spear from the resemblance of its leaves to the ancient weapon.
When in flower, they are mostly very attractive to insects, especially butterflies, hoverflies and bees so their place in the food chain is very important. In the old days, thistles in pastures were cut down by scythe and many were missed, but with the much more efficient herbicides of today, most are wiped out completely in one application leaving only those on waste ground and inaccessible areas available to insects.
Once the flowers are past, seeds are carried on fluffy parachutes on the wind and can travel great distances. As a result, thistles are great colonisers of bare or disturbed ground and along with rosebay willowherb, are usually the first plants to become established.
“How did the thistle become the unlikely emblem of Scotland?” I hear you ask. There are many stories and theories about how this happened, but I think the most popular is this: According to 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 on 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, but it is not certain.
The species involved was probably the spear thistle as this seems to be the one represented on most heraldic illustrations over the years.