Frost

 Does the temperature have to be at or below freezing for frost to form on
plants?

Thanks

 

http://en.wikipedia.org/wiki/Frost

  Notice the mention of dew point.

 Bill who thinks the frost acts like a magnifying glass hence the plants
burn.  Not sure if this is correct only know that late frost about here
has me out spraying water on tender new plants.

--
Garden in shade zone 5 S Jersey USA

We have 5% of the world's population; we have 25% of the world's
 known prison population.





 

 On 3/28/2009 12:53 PM, Bill wrote:

Liquid water from a hose is above freezing.  In the process of turning
into ice, such water must first give up heat just to be chilled to 32F
(0C); then it must give up significantly more heat just to become ice
even if the temperature remains at 32F.  That's why farmers in my area
spray water on citrus, avocados, strawberries, etc if there is a late
freeze.  For "radiation frost" with air temperatures above freezing
(described in the Wikipedia article you cite), they do nothing since
those crops are generally hardy enough to withstand the chill.

--
David E. Ross
Climate:  California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at <http://www.rossde.com/garden/diary>

 wrote:


For moisture or water to freeze the temperature must be no higher than
32 degrees F, and then additional heat must be removed for the water
to phase-change to a crystal lattice structure (ice).   No ice will
form above 32 degrees, but certainly there can be supercooled (or
contaminated) liquid water below 32 degrees, which is added frost
protection for the plant.

 

Below freezing, because the plant(s) will carry over some heat from the
day and the ground, if dry, will be reflecting some heat as well. This
heat must be removed before freezing can occur. As Bill alluded to, as
long as your making ice (there is water to freeze) the ice will remain
at 32F (0C).
--

- Billy
"For the first time in the history of the world, every human being is
now subjected to contact with dangerous chemicals, from the moment of
conception until death."  - Rachel Carson



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