Originally Posted by Unregistered

You need those to evolve your 4 to 6 star Flower Knights.

I think they started to appear when the winter rose garden backtheme was introduced, so it probably was with the holly event (?).
All of the 4 colours can appear though they seem to be pretty rare. What they say doesnt seem to have meaning, at least i haven't heard any suggestion about it.
That's pretty much all i know about them