Astonishingly, the picture to the left shows not a flower growing out of a stem, or even candy floss or the hair of a back-combed terrier, but just ice. This ice is actually growing out of the plant stem in the sense that the mechanism by which it forms is roughly as follows.
Overnight, the temperature outside the plant stem drops below zero and so water in pores or a crack in the stem freezes. Then the water continues to freeze and as it does so it draws more water from the plant which pushes the ice out into long thin tendrils which are basically extruded from the plant stem. I guess the difference is that when say toothpaste is extruded from a tube it is pushed out, while here freezing acts to pull the freezing water out. As the cold temperatures outside the plant freeze water, more is sucked out from the plant.
A retired professor in Illinois, James Carter, has studied these beautiful things, and wrote an article in American Scientist where I came across saw ice flowers for the first time. His website has many amazing pictures of them, as does that of another American professor, Bob Harms. It is amazing that something as commonplace as ice forms these beautiful structures, but it can. It can even form really weird ‘meadows’ of flowers on the surface of cold water, see here for some amazing pictures.