Frost forms when an outside surface cools past the dew point. The dew point is the point where the air gets so cold, the water vapor in the atmosphere turns into liquid. This liquid freezes. If it gets cold enough, little bits of ice, or frost, form. The ice is arranged in the form of ice crystals.
Types of Frost
Radiation frost is frost in the form of tiny ice crystals that usually shows up on the ground or exposed objects outside.
Advection frost is a collection of small ice spikes. Advection frost forms when a cold wind blows over the branches of trees, poles, and other surfaces.
Window frost forms when a glass window is exposed to cold air outside and moist air inside. Window frost is familiar to winter residents of cold climates. Indoor heat and cold outdoor temperatures cause this type of frost.
Rime is frost that forms quickly, usually in very cold, wet climates. Rime also forms in windy weather. Rime sometimes looks like solid ice.
Frost and Plants
Frost damage occurs when ice forms inside the plant tissue and injures the plant cells. Frost damage may have a drastic effect upon the entire plant or affect only a small part of the plant tissue, which reduces yield, or merely product quality.
Direct frost damage occurs when ice crystals form inside the protoplasm of cells, whereas indirect damage can occur when ice forms inside the plants but outside of the cells. It is believed that direct frost damage causes problems for protoplasmic structures.
Although the evidence is not strong, it seems that the rate of thawing after a freeze is also partially related to the amount of damage. Citrus growers in southern California commonly believe that slowing the warming process after a freeze night can reduce frost damage. In fact, growers justify operating wind machines longer into the morning following a freeze night in order to slow the thawing process.
Usually there are still a couple of good weeks of weather after the first frost. While the first frost announces the coming of winter there are some things one can do to protect plants:
- Harvest early
- Irrigate before the frost
- Cover your plants
- Irrigate during the frost
- Chemical sprays
- Heaters and wind machines
Additional Information
Understanding Frost - Cornell University
Frost protection: Physiology and Critical Temperatures - United Nations
Frost - National Geographic
