The frost I am referring to is HOAR frost (the white ice crystals you can see). And YES I am talking about it on PALM
fronds, leaves, NOT
on the ground, grass. NOT
on objects that loose heat much faster than plant tissue, like metal cars,windshields,patio chairs,lawn oraments, however when it forms on the plants,at least here it is on those things also!It can kinda look like it snowed to anyone who has never seen snow before,but it is not snow it's FROST!
And as I said before it will do a serious number on certain palm foliage if it forms on them, even if the ambient temp in the air isn't below freezing! That was my reason for the question in regard to this data base, asking if the palms saw frost.[/quote]
I think I can see now where this "failure to communicate" is coming from. Now if I can only communicate it.
Now keep in mind that I am speaking of my experiences in coastal San Diego County, but I believe this holds true for 99% of the "agricultural" areas of SoCal (i.e. south of Santa Barbara, excluding mountains and deserts).
We do not experience advective freezes here. If the wind is blowing, we don't freeze. We only experience bad freeze damage when the nights become very clear and very calm, and these conditions occur almost exclusively when it is also very very dry. The reason being these clear cold air masses arrive from the deserts to our east, and therefore are very dry.
Let me quote happ, our weatherman:
"The arctic air mass in California, unlike what Texas is currently observing, was extremely dry. There was little if any clouds and with dew points/relative humidity well below 20% the night time temps plunged. Low humidity is common during winter & certainly during offshore winds."
Do you ever get relative humidity well below 20% in Florida? In California there is never frost during the most severe freezes. That is why I breath a sigh of relief when I see frost forming (on the ground).
So to overly simplify this thinking --- when the air is moving and/or there is some moisture in the air (visible frost on the ground) we will not suffer a hard freeze.
If you will notice. Unless I missed one or two, everyone that mentioned frost in SoCal in the data section indicated "no frost." So for me, when I see frost (moisture), I know the air mass arrived from the north or west, and therefore has some maritime influence from the ocean, as opposed to the bitter dry Canadian cold arriving out of the east. These "maritime events" may get to 28,29,30 degrees on rare occasions in certain locations, but will never get colder than that unless it is dry, clear, and calm.
This leads in to my next point on why I believe you guys are so concerned about frost on your palm leaves and we are not. First, as I mentioned in another post, in most cases (at least in coastal areas here) we never experience frost on leaves. It is never cold and wet enough at the same time for this to occur. Again, when a Californian says frost, he means frost on the ground or other objects, not on foliage well above the ground.
This is what you said that explained to me why we view this topic differently: "FROST can be devastating here in Florida even when temps don't go below freezing. There are certain palms that will not tolerate FROST here at all veitchia,kings,foxtails, and royals are a few."
Yes, frost on the leaves of a tender palm will be damaging, because if a palm is damaged at 32 and there is ice on it, there will be damage, regardless of what the thermometer says. However, in California, if there is frost on the ground, that does not mean the air temp at 6 feet is 32. In fact it could be 35 resulting in no palm damage to the same tender palm. You say there was frost and my Vetchia was damaged, and we say we had frost and no damage. But again, no frost here indicates it could get much colder than that.
Another reason for your heightened concern with visible frost may be the following. I am guessing that as a rule you guys are growing more of the marginal palms than we are. That is, the palms that will damage at 30-32, and therefore frost formation on their leaves causes considerable damage. We just don't grow a lot of those palms here, the Veitchias, the Arecas, the Ptychospermas. I have none of those in my garden of a few hundred palms. IMO, we grow more of the palms that even if we saw frost formation on their leaves, it would not cause damage. So to us it is of little or no concern.
So, to summerize:
Frost to us is frost on the ground, and indicates a mild freeze which will not really damage the majority of the palms we are growing. No frost indicates a possible bitter dry cold event with temp readings in the mid to low 20 and severe damage to most palms.
Frost to you is frost on the leaves, and indicates damage to your marginal palms regardless of what the temp readings may actually indicate.