From a children's book called The Little White Bird by J.M. Barrie, illustration by Jean Winslow. This story was one of the precursors to the Peter Pan story.

When you were a bird you knew the fairies pretty well, and you remember a good deal about them in your babyhood, which it is a great pity you can't write down, for gradually you forget, and I have heard of children who declared that they had never once seen a fairy. Very likely if they said this in the Kensington Gardens, they were standing looking at a fairy all the time. The reason they were cheated was that she pretended to be someting else. This is one of their best tricks. They usually pretend to be flowers, because the court sits in the Fairies' Basin and there are so many flowers there, and all along the Baby Walk, that a flower is the thing least likely to attract attention. They dress exactly like flowers, and change with the seasons, putting on white when lilies are in and blue for blue-bells, and so on. They like crocus and hyacinth time best of all, as they are partial to a bit of color, but tulips (except white ones, which are the fairy cradles) they consider garish, and they sometimes put off dressing liike tulips for days, so that the beginning of the tulip weeks is almost the best time to catch them.