December 15, 2018

Frost occurs when surfaces reach a temperature at or below freezing level. Once surfaces reach this level, they are covered in a multitude of tiny ice crystals. However, windchill can also contribute to a frost occurring by freezing the moisture within plants. When ice crystals occur, the proper term is “hoarfrost.”

While a freeze means temperatures drop significantly below freezing, regardless of causing or not causing ice crystals. Although geography determines when a freeze is declared, typically a freeze warning occurs when the temperature will be sub-freezing for long enough to damage vegetation.

Differences Between a Frost and Freeze

While the two terms are related, a frost is typically regarded as milder than a freeze, generally ranging in temperature from 36 to 32 degrees F. Freezes, on the other hand, entail at least a 4/5 chance temperatures will drop below 32 degrees F.

Furthermore, frosts typically occur on clear nights, when there are no clouds to retain heat from the day. Freezes are associated with high levels of cold wind and minimal humidity. Both frosts and freezes come in varying degrees.

Kinds of Frosts and Freezes

  • Light Frosts are when some heat is still retained by the ground at night. This often results in the tops of plants dying from frost exposure, while the bottom portions remain unharmed.
  • Frosts/Light Freezes occur at 32 degrees F. Significant damage is unlikely at this temperature but ultimately depends on the topography of the environment.
  • Moderate Freezes have a range of 29 to 32 degrees F. Sometimes they are called “killing frosts,” as tender plants such as flowers generally are killed. However, the majority of other vegetation like bushes and trees remain unscathed.
  • Hard/Severe Freezes will wipe out all but the most sturdy vegetation and are associated with the term “arctic blast” because they involve a mass of cold air moving into an area. Hard/severe freezes occur at 24 degrees F and below. Walking on the ground during a hard freeze will often cause it to crunch.

Protecting Vegetation

  • Watering plants will actually provide a natural insulation. Surprisingly, well-watered soil can retain up to four times the amount of heat as parched soil. Although the idea is to protect against the cold, a layer of ice can, in fact, serve as protection. However, this is only in the case of frosts and is unlikely to help during freezes.
  • Covering plants is useful for both frosts and freezes. This does not guarantee protection against damage, but will definitely diminish chances of vegetation dying during cold weather. Any kind of object or sheet which can properly cover the plants should suffice. Once temperatures warm the following day, remove coverings and keep them on hand for future use.

If you are interested in learning about ways to protect your landscape this winter, contact Twin Oaks Landscape today!