‘Tis the season for a nightly freeze or frost warning.

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Posted by justtracy | Posted in Gardening, Weather | Posted on 08-04-2012

Before freeze damage

Frost or Freeze? These are actually weather terms.

A freeze is when the air temp drops and remains below 32 and the winds are above 10 mph.  We may experience these conditions all winter, but in the spring when we the sun is creeping back to the northern hemisphere, our day temps get warmer and warmer but the night temps drop back below freezing. For everyone (but maple syrup producers) this can have a detrimental effect on our plants depending on how far along plants move toward flowering under sustained warm day and night time temperatures.  When a freeze occurs, the cells within the bud or foliage that have already emerged  will swell just like if you put an unopened soda in the freezer.  At some point that cell ‘pops’ and releases the fluid inside.  The result is what looks like burned flower buds or foliage.  It may take hours or days for the damage to fully become visible as the cells warm up and the oozing begins.

After freeze

Freeze damage usually affects trees and shrubs in early spring because these are plants that are outside  year round and you can’t normally go out and just cover up.  Damage to fruit trees can be especially concerning to commercial growers.

Frost on the other hand, requires three atmospheric conditions to occur: 1) temps near or below 32 degrees; 2) little or no wind  3) a high dew point.  When all three of these conditions occur, ice crystals actually form ON the plant.  Most trees, shrubs, perennials are frost hardy.  It’s those tender perennials and annuals that can’t take frost like petunias or tomato plants.  It’s the ice crystals ON the plant that actually cause the damage to the tissue of the plant.  The appearance may look the same as a freeze.

For the last average frost date for your area, contact your local cooperative extension. It’s also good to keep a garden journal to record your  last frost dates for future reference.

Here are a few links for more information:

 

 

 

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