How Does Frost Harm Plants?
On cold winter mornings, feathery designs of ice may form on windowpanes and blades of grass. These icy crystals are frost. Frost kills crops, and is a serious danger to the farmer and the plants.
Frost is formed when the temperature falls below freezing. The water vapor in the air freezes into tiny crystals of ice on the cold surface of a plant or other solid object.
Ground frost occurs when the temperature of the ground falls below freezing point (0ºC/32ºF) and air frost occurs when the temperature of the air falls below freezing point.
Plant cells can be damaged or even destroyed by frost. Repeated freezing and thawing, or very rapid thawing can be particularly damaging to plants.
But it isn’t the frost itself that kills the plant. The plant dies because the low temperatures that cause frost also cause the plant juices to freeze and expand, bursting the delicate plant cells.
Once the temperature has fallen below freezing, a strong wind can make a frost more damaging.
Cold winds remove moisture from evergreen foliage more quickly than it can be replenished by the roots; this can cause leaf browning particularly at the tips and margins.