Hoar Frost

Wikipedia reports that “If a solid surface is chilled below the dew point of the surrounding air and the surface itself is colder than freezing, frost will form on the surface. Frost consists of spicules of ice which grow out from the solid surface. The size of the crystals depends on time, temperature, and the amount of water vapor available.

The name hoar comes from an Old English adjective for showing signs of old age…, in reference to the frost which makes trees and bushes look like white hair.