There is a very unintuitive method of protecting fruit trees from a late spring frost (which can be deadly for fruit crops) on a day when temperatures fall far below freezing in the early morning: the trees with their blossoms and buds are sprayed (from a sprinkler system) with water which keeps freezing on them and protects the plants underneath from getting too cold by giving up the latent heat of phase change as it freezes. One must keep the water spray on as long as the air temperature is below freezing. More information about this method is here.
You can see how dramatically beautiful the apple orchards look in this photo I took in the town of Vahrn, South Tyrol, last week. Imagine row upon row of these crystalline dwarf apple trees shining in the sun.