The thistle flower heads are all beginning to die as the flowers turn to the light downy material that floats through the air on the breeze, sparking interest in the natural world for many children as they rush around trying to catch the "fairies" (I've done this plenty of times :) to make a wish on.
But they are also useful for a different kind of sparking; they are excellent for use as a tinder. The down catches a spark easily and flares up quickly, perfect for use when trying to ignite coarser tinder materials, such as dried grass. I have also used it on the two rare occasions where I have got an ember from the bowdrill to enlarge the ember; some thistledown placed in the centre of the tinder bundle makes it so much easier to get a flame. This is just an example of how plants that are considered a bane on gardens by others can be useful for others.