[Arid_gardener] Fwd: Navel orange tree

[Dick]

Carl, I have tried several tricks or techniques to protect plants from frost damage when the weather man issues warning but only then. It is too much trouble otherwise. I have not always been successful, however. I have used Xmas lights on many ocassions and found the method effective but would be hard pressed to prove it.

A standard practice in California some years ago was to flood basins. As water freezes it releases heat and it apparently works except that it causes a muddy mess and, if several days of frost strike, the duration is itself a problem.

One year I used an oscillating water sprinkler that covered nearly everything in my yard. I awoke early the next morning to find that the sprinkler had siezed but my citrus was coated entirely with a coat of ice a quarter of an inch deep in some places. Assuming everything was lost, I was sick. But, to my utter amazement, after everything thawed, not a leaf was damaged. The ice provided absolute protection. That phenomenon can be easily explained by physics but the logic escapes me at this moment.

I have used Christmas tree lights, heat lamps,  kerosene  pots and any other heat source I could dream up to create air circulation. I don't believe it was the heat alone.  The friction caused by air molecules against one another and the friction it causes in foliage generates heat and freezing is unlikely under these conditions unless it is a hard freeze of long duration like two or three hours for which, in my opinion, there is no effective protection except a heated greenhouse. Every severe frost damage I have experienced in Phoenix and on the West Coast occurred when the air was dead still. I would assume similar circumstances would prevail in any Mediterranean-like climate.

The most effective protection for me has been a large, industrial, oscillating fan on a pedastal. It covers my entire yard with an air flow. In California, I once observed that it would never freeze when there was a breeze and a fan creates a current. California citrus growers have for years used airplane propellers positioned above the canopy to circulate air when the orchard was threatened by frost. Years ago in Chula Vista, Ca., the early morning air would be black with soot from diesel and stove oil burners in orchards.

I have used bed sheets effectively  but, on other peoples advice avoid plastic covers unless you can prevent any contact with foliage like in a greenhouse.

Small plants are effectively protected with sheets but most advocates insist that coverage should be all the way to the ground.

Dick Gross, MVG, U of A
Maricopa County Cooperative Extension
  ----- Original Message ----- 
  From: Carl R King 
  To: rkgross3 at cox.net 
  Sent: Sunday, November 25, 2007 7:26 AM
  Subject: Re: Re: [Arid_gardener] Fwd: Navel orange tree


  Hi Dick,

  I've written you asking about my navel orange tree and how to get the then 36 yr old tree to bear fruit again.  I'm happy to report it has many oranges as I write.

  My question concerns keeping shrubs safe from freezing.  Would placing standard-sized outdoor Xmas lites on it generate enough heat to ward off the freeze?  I purchased these shrub after assurances they could withstand freezing.  Last years freeze did severe damage although you wouldn't know it today.  I'm hoping the heat the bulbs put out would be enough to offset the cold.

  Thanks again for being there.

  Carl 
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