This morning we had to visit the west end of Glasgow early in the morning, so I was keen to go and have a look to see if the flowers of Jack-go-to-bed-at-noon, which I had seen there before, would be open. Sure enough, at 9 o'clock in the morning there were two flowers open in the sunshine.
Jack-go-to-bed-at-noon (Tragopogon pratensis ssp. minor), also known as Goat's-beard, earns the first of these names by its habit of opening its flowers only on sunny mornings, closing them again at around noon. In ssp. minor the bracts are much longer than the yellow florets.
Some time ago I took a sequence of pictures of one flower at intervals through the day, and this composite image shows what happened.
The roots of the closely related Tragopogon porrifolius, or Salsify, are used as a vegetable.