It is as beautiful as it is rare. A frost flower is created on Autumn or early Winter mornings when ice in extremely thin layers is pushed out from the stems of plants or occasionally wood. This extrusion creates wonderful patterns which curl and fold into gorgeous frozen petioles giving
this phenomenon both its name and its appearance.
Conditions have to be just so for frost flowers to form.
Early Winter is the optimum time to come across them as although the weather conditions must be freezing it is vital that the ground is not, so water can be sucked up in the stem.
As the temperature gets to freezing or just below the sap in the stem of the plants will expand.
As it does so, the outer layer of the stem comes under increasing pressure, and microscopically thin cracks, known as linear fissures, begin to form.
These will finally give way under the pressure of the sap and split open forming cracks for the water to come out through and then freeze.
Water is continuously being drawn up the plant ‘s stem while the ground remains unfrozen. It travels up the plants external structural axis (stem!) and reaches the split or splits. As it does so, it oozes slowly out and it freezes. Yet more water is coming behind it. This new water reaches the cracks and it too freezes, pushing the previous slither of ice away from the stem. And in this manner the amazing ‘petals’ that you see in these pictures are formed.
Incredibly, the frost flower effect can happen to wood even when it has been made in to a fence or a gate, as seen above. In this case the water is extruded through the pores in the wood rather than cracks.
The frost flower has a number of other names: you may know them as frost castles, ice castles, ice blossoms, or even the very scientific sounding crystallo-folia.