What Does Frost Mean to You?

[Dypsisdean]

It seems to me that "frost" means different things to different people. When used in the following contexts, what does "frost" mean to you?

"inland from me people probably experienced a light FROST"

"I can confirm the FROST readings in inland locations."

[Kim]

All of the above.

[LJG]

Unfortunately the very definition can make it confusing in the plant world.

frost  (noun)

- a covering of minute ice needles, formed from the atmosphere at night upon the ground and exposed objects when they have cooled by radiation below the dew point, and when the dew point is below the freezing point.  

- the act or process of freezing.  

It has two separate meanings when it comes to plants. Freezing is not as bad as frost (formation of ice crystals) on plants. So when I hear frost, I think ice crystals. Freezing is below zero. It will be interesting what others put.

[Palmarum]

Frost means a very, very bad day to me...

Ryan

[ruskinPalms]

Dean, frost to me is anytime I see the white frozen, maybe kinda 'fuzzy' stuff on any surface - be it roof tops only or on every possible surface. Ice to me needs to be clear, a bit more solid not 'fuzzy'. I think the confusion comes from light to heavy frost and everything in between. The air is usually so dry in Cali that I guess only light frost forms during very cold radiational freezes. Probably, the car tops, roof tops and grass in this latest cali freeze cooled off the quickest causing dew to form on them first sucking what available moisture out of the air before the palm leaves and other things that seem to retain heat had a chance to form a dew that would have later frozen into frost. Maybe I am wrong about it being dew first as maybe it jumps directly from water vapor to frozen water (frost), but the surfaces I mentioned would still cool first sucking the moisture out of the air with the same end effect. I personally think that if conditions in FL supported a radiational freeze down to the low 20's then the water vapor content of the air would be similar to what it was in this latest cali freeze, thus a low 20's radiational freeze might create the same type of rooftop, car glass frost that was seen in cali. Usually, radiational freezes here are higher in temp, the temp being held up by the greater water vapor content in the air. The lowest temps here in the low 20's come from advective freezes when frost would not form. I think I read posts from people california that did indeed get frost on their palm leaves in the days following the first major, dry radiational freezes. They had lots of nights with high 20's to low 30's with frost more like what is often seen here in FL.

[gsn]

I totally agree with RYAN!    

(a) Temperatures dropped below 32 degrees F.

NO it can freeze without there being FROST!

( Visible frost on the ground (grass), cars, roofs, or other inanimate objects.

POSSIBLY ,if it forms on the grass, I would consider that a light FROST! And I would definately check closely to see if it formed on other plant surfaces as well!

If it only forms on inanimate objects ,like  glass windows, cars, roofs NO. As these objects radiate (transfer) their heat into the atmosphere much more rapidly than plant material.

c)Specifically refers to frost on the surface of the leaves of plants.

YES,  if it forms on the plant material you definately had FROST!

[Dypsisdean]

(ruskinPalms @ Jan. 26 2007,19:25)

QUOTE

I think I read posts from people california that did indeed get frost on their palm leaves in the days following the first major, dry radiational freezes. They had lots of nights with high 20's to low 30's with frost more like what is often seen here in FL.

Bill,

This is the point I am trying to clear up. You may have read from a very few SoCal growers that they experienced frost. I think you then assummed they meant frost on the leaves of their palms, when they were referring to frost on their lawns or car.

[osideterry]

I have to think of frost as visible ice crystals. I see it on my car windshield 2-3 times a year, when the outside temperature is 36-38F. Most of the time it hits freezing here when the humidity is under 25%. I saw zero visible frost through this last freeze in socal.

One very cold morning I could make out a semi-visible web-like/crystal pattern on the hood of my car. Not really frost, and gone as soon as things warmed up.

[Dypsisdean]

Scott,

Correct me if I am wrong.

When you guys in Florida worry that you may have frost, and say that frost damages your palms, and when you ask a fellow grower if they had frost last night..................you mean frost on your palms, don't you?

[ruskinPalms]

Sorry all   , I am new to all of this. Bottom line: my definition is that you had a frost if you see the fuzzy white stuff, web patterns etc. on ANY surface. That is how I would personally report whether I saw frost or not. Maybe it is so common in some places to see that on the car glass, grass, roof tops etc. that you don't consider that frost until the goods in the garden are feeling it. I do consider any white stuff that is not from snow as frost. It is not common (no more than 1 or 2 nights a year since I have lived in west central FL, moved here from IN in 1997) to see this on the cars, grass and roof tops let alone all over everything like last Feb 14th. If I reported to this board, I might say something like "I had a light frost last night that showed up on the rooftops and cars in the neighborhood, but I could not see any on the plants in my garden."

[Zac in NC]

The first option in my opinion is a freeze. The second and third ones are frosts. I see both all winter long. I hate them, but I just have to deal with it right now.

Zac ( I voted the second option)

[Neofolis]

I voted for visible frost on leaf surfaces, option 3.

Being in an area that sees regular frost, but having a small, enclosed garden that sees much less frost, I am only concerned about the frost I see on my palms.  Generally I think of frost as the formation of ice crystals on any surface, but in the context of palm growing, I don't care if there is frost everywhere else, if it is not on my plants.  I can't determine my plants to be frost tolerant, just because there is frost 10' away from them, so unless it is on the plant, they have only be exposed to low temperatures.

[gsn]

(Dypsisdean @ Jan. 27 2007,00:49)

QUOTE

Scott,

Correct me if I am wrong.

When you guys in Florida worry that you may have frost, and say that frost damages your palms, and when you ask a fellow grower if they had frost last night..................you mean frost on your palms, don't you?

Dean,

You are absolutely CORRECT!

At least that is what this Floridian is saying,can't speak for everyone! ::

My mom  lives in inland central Florida,just south of Kissimmee.If I am not there helping her out durning a cold event,here is the morning after phone conversation,pretty much in this order,unless she tells me everything is BROWN covered in WHITE.

Goes like this, did you have ice on the car or windsheilds,yes/no

Was there ice/frost on the lawn,yes/no

did the palms/or shrubs have FROST on the foliage yes/no

[Dypsisdean]

(ruskinPalms @ Jan. 26 2007,19:59)

QUOTE

Sorry all   , I am new to all of this. Bottom line: my definition is that you had a frost if you see the fuzzy white stuff, web patterns etc. on ANY surface. That is how I would personally report whether I saw frost or not. Maybe it is so common in some places to see that on the car glass, grass, roof tops etc. that you don't consider that frost until the goods in the garden are feeling it. I do consider any white stuff that is not from snow as frost. It is not common (no more than 1 or 2 nights a year since I have lived in west central FL, moved here from IN in 1997) to see this on the cars, grass and roof tops let alone all over everything like last Feb 14th. If I reported to this board, I might say something like "I had a light frost last night that showed up on the rooftops and cars in the neighborhood, but I could not see any on the plants in my garden."

Bill,

As a Californian, I think that is how everyone in California uses the term.

However, I think some in Florida use it when referring specifically to frost on plants. That is what I hope to clear up.

Because if someone in Florida wants to know if there was frost on someone's palms, he may ask, "Did you experience frost?" To which the Californian will answer yes if he saw a little frost on his car in the morning, yet his palms were frost free and undamaged.

In that case the Floridian can not figure out why frosts in California don't damage palms.

[ruskinPalms]

Ha   . I am glad we are getting this cleared up. All of you out there. Please report all, any frost that you see in your area whether you see it on the palms or not. Chances are, there was a little frost on your palms even if it was very short lived. Just go out and check a leaflet of a frond by smashing it between your index finger and your thumb, if you feel a melting sensation then uh oh.

[gsn]

Bill,

That is why I said if you see it in the yard (GRASS), rather than on inanimate objects like cars,  windows,and roofs.

One should check very carefully to see if it is also on foliage up off the ground including palm fronds! :: Because I too beleive that if forms on the grass there is a GOOD possibilty that it formed on the leaves of other plants above the ground,even if they aren't covered in noticable white ice crystals. Therefore it could be missed if not checked closely!

Although I will concede that it could  be only a ground covering event and not any higher!

[Walter John]

means frost for f#%@s sake, what's this doing here. Isn't there a weather/climate section ? You all been drinking ?

[ruskinPalms]

(Wal @ Jan. 27 2007,01:53)

QUOTE

means frost for f#%@s sake, what's this doing here. Isn't there a weather/climate section ? You all been drinking ?

That's a sobering reply Wal  ::  But this is a philisophical discussion of the nature of frost and in what context it is defined. I, myself, agree with your simplistic concept of frost. Frost is frost  

[aussiearoids]

Isn't it a layer of sugar on a cake ?

Thats all I've seen ever here  :cool: .

[Dypsisdean]

Wal,

You're right. I'm using executive privilege.

I got tired of what appeared to me to be a lack of communication due to a lack of agreement on terms.

I thought it important to find out if we were talking about the same thing when we said frost. And it appears we are not.

[Wai`anae Steve]

Any night it goes below 70 F.

Tee Hee                       :laugh:

[gsn]

(aussiearoids @ Jan. 27 2007,01:58)

QUOTE

Isn't it a layer of sugar on a cake ?

Thats all I've seen ever here  :cool: .

Aussiearoids,

That would be FROSTING!

Not to be confused with FROSTED,which is apparently what WAL is about this thread! :laugh:

[Phil]

Two definitions off the Net for "Frost":

1.  From Encarta

a.  frozen water: crystals of frozen water deposited on a cold surface

b.   freezing temperature: an outdoor temperature below freezing point, resulting in the deposit of ice crystals

2. From Arctic Climatology and Meterology

Frost: The condition which exists when the temperature near the Earth's surface and Earth-bound objects falls below freezing (0 °C or 32 °F).

For me personally, I think of the following:

Frost you see

Freeze you measure

Phil

[quaman58]

Regardless of how I may define frost; a question: Does the fact that I regularly (this year) have a thin layer of ice on the roof of my vehicle (and nowhere else that I can see), REALLY mean that the outside temp reached freezing? Or can the conductive properties of metal create ice when it's just close to freezing? Up till now, if I see ice there, it must be a frost I've thought. Now I'm not sure whether that's correct or not. Any metalurgists out there?

[STEVE IN SO CAL]

Frost is baad...n-kay?

[happ]

Interesting discussion about an amazing weather phenomena.

I found this definition on the Texas Citrus site :

http://aggie-horticulture.tamu.edu/Citrus/cold/L2287.htm

Types of Freezes

There are basically two types of freezes which can damage citrus--advective and radiational. An advective freeze is characterized by a massive outbreak of very cold arctic air which blows rapidly across the plains and into South Texas. Strong, northwesterly winds and cloudy conditions predominate, usually over several days, with occasional precipitation. If precipitation occurs, strong winds cause evaporative cooling, which reduces the temperature of plant tissues below air temperature, thereby causing even more damage.

Towards the end of an advective freeze front, the skies often clear and the winds subside, which results in a radiational freeze. Without cloud cover to trap radiant heat or wind to mix the air, radiant heat energy from the earth is lost to space, resulting in very cold conditions at the surface.

If one recalls the outbreak of arctic air that swept from the West Coast & Mountain States into the Plains was along a cold front.  With extremely limited moisture as a result of due-north contintental air, little if any rainfall occured.  So the advective freeze front was dry per the norm in California.  Sunshine helped keep maximums in the 50's & where there was wind, the minimums remained above freezing. Wind sheltered areas were overwhelmed in the dry arctic atmosphere with rapid/raditional cooling after sunset.

As Jim has shared, San Antonio barely dropped below freezing since subtropical jet was overhead.  The rain feel into a very cold lower level of arctic air.  Unfortunately ice resulted rather than frost & clouds suppressed maximums.  No radiant frosts occurred during this episode in Texas [i believe].

[BS Man about Palms]

Bret-

Metal has nothing to do with it. Matt in SD had a good explanation on another thread.  Apparatus dewpoint is the point at which the "surface temperature" of ANY object, (glass, metal, wood, plants, etc) will allow condensation or dew to form on the surface.

The difference I think between Fl an Ca as a whole is the humidity at these "freeze points".

To continue, the higher the humidity, the higher the dewpoint.  In other words for instance, if it was 60% R.humidity, you might see dew/condensation on a surface of something at 52F when it is 58F outside. (again, SURFACE TEMP) whereas, at 25% R.humidity, the surface temp might have to be 42F for dew, at the same 58F outside temp. (please realise I did not pull out my book to get the exact numbers, I'm just showing rough corellation)

NOW, once you have dew/condensation/moisture on a surface, once that surface reaches 32F, it FREEZES.  It may not be 32F outside to do this!

(Here is the point that Matts description of moisture, humidity, plant health, etc. may serve to keep the surface of a palm leaf HIGHER in temp than the surrounding air if it is humid and healthy enough. Maybe Matt or Dean can insert, or direct us there)

I knew most of this, just never till recently thought about it in reference to plants, just the air conditioners I work on.

[quaman58]

Okay...I had to read it through a few times, but I think I'm beginning to get it. Thanks for that..

[Jeff Searle]

To me, frost is frost. Weather you had a little on plants or some on the windsheild. In any case, its a bad time, for anyone trying to keep thier tropicals alive.

 And it can frost with conditions right, above 32 degrees.

 Here at the nursery, what most growers have learned over the years, is when temperatures start approaching say 32-35 degrees, and we start to find the first sighting of frost on the ground or where ever,we then turn our big pumps on to water the entire nursery. We run them at idle speed only, just enough to wet the plants. Then usually a thin layer of frost will form and act like an insulation on the leaf. The pumps can run all night and into the morning, and are only shut off when the the ice is fully melted of the plants from the sun coming up. This has happened once as late as 11:00 am in the morning!! It's not a pretty sight by any means.

Jeff

[BS Man about Palms]

(quaman58 @ Jan. 27 2007,09:18)

QUOTE

Okay...I had to read it through a few times, but I think I'm beginning to get it. Thanks for that..

Bret-

 

I'm sorry that I didn't add the conditions such as evaporation, radiation, convection that allow a surface temp to be cooler than the surrounding air.  Admittedly its rarely more than a couple/few degrees, unless by mechanical or assisted methods.

One of the visuals I have told customers over the years is to remember a coke or something that starts cold then slowly warms up, did you notice its "sweats" more on a humid day? Its the condensation forming on the surface.  At the other extreme, on a cool morning, a big Mug of coffee will "sweat" inside the mug.  Hot enviroment, cool mug, surface cool enough to condense the coffee and moisture vapors on the inside.

Hope that helped a little.

Jeff- I agree, any frost is bad!!!

[Kathy]

Very interesting -- never realized we can think so differently about this.

Maybe I'm like most Californians:

I check my grass first.  If it's covered in white ice crystals and crunchy, then frost!  I don't care about checking a nearby palm in validation;  I know my palms felt something.

I glance at cars too, but grass is always my first look.  Even if I see frost no where else when looking, I'll report frost occurred.

[BS Man about Palms]

Kathy-

I think Dean is on the right track, I don't think we think so different, its just certain areas NEVER see any different.  Up until this year I had what I called "frost" only twice in the past 11 years. It was only in a few spots at sunrise, so that to me was frost, although there were areas nearby (in the same yard) that did not get any frost on a surface. So, in theory, although if it was a plant, it may have been stressed, but did not get frost.  ??

The plant part is what I need Matts post to help on.

Oops!  It was Jack-  I just took a while to find it.

---------------------------------------------------------------------

Here's a quick summary comparing what I think happens in frosty freezes and dry freezes.  More details below for those who care:

dry freeze = slightly colder palm leaves, much less time below freezing

frost/humid freeze = slightly warmer palm leaves, much more time below freezing.

Maybe some plants are more sensitive to the duration of the freeze, which makes frosty/humid freezes worse than dry ones in some cases...

------------------------------------------------------------

I've devoted a LOT of time to studying microclimates.  It's very confusing and complicated, and most of it went over my head.  But, here are some things I think I understand.  I've left out a lot of details so this won't take forever to write/read....

1) At night, objects on the earth's surface radiate energy out to space.  These objects become colder than the air around them, so energy from the atmosphere is transferred to these objects.  By transferring energy to these objects, the atmosphere cools down, and we record the temperature of the atmosphere.  

2) Temperatures of plant leaves have been measured at night.  On very clear, dry nights the surface of an average size leaf tends to be about 2C (4F) colder than the ambient air the surrounds it.  

3) As the amount of water vapor in the atmosphere increases, the temperature of the leaf surface is closer to the temperature of the atmosphere around it, so it's slightly warmer than on a dry night.  

4) So, for a given temperature (say 0C = 32F), the lower the relative humidity the colder the palm leaf.  This means that the dry freezes we've been having in SoCal produce colder palm leaves than the frost forming freezes in Florida.

So, it seems like a dry freeze will be more damaging that a freeze that produces frost on the leaves because the leaves will be a little colder.  But, observations from Florida seem to contradict this conclusion, and I think I know why thanks to a post from Ray.  He said the temperature fell below freezing at 4PM when he had a low of 24F in 1989 and didn't rebound until 11AM.  In this SoCal freeze, the places that hit 24F didn't drop below freezing until maybe midnight, and recovered by 8AM.  So, for a freeze of a given temperature, the dry one will be shorter.  This is because the temperature changes more quickly on dry nights because water is a very efficient greenhouse gas.

--------------

Jack Sayers

[BS Man about Palms]

Dang!

I may have jumped the gun- I didn't read it all. Maybe it was Matt that had more explanation.  Matt?  Jack?

maybe I should just go hold my palms hand/frond and help them through this traumatic time!!!   :cool:

[ruskinPalms]

I wasn't around here in FL in '89. That was an advective freeze, a radiational freeze or both?  ???

I have always thought the really cold temps during the 89 event came from advection of cold air. I think there were radiational nights following, but not as cold. I am totally guessing on this, but I would think that when comparing a dry radiational event to a more humid radiational event, the dry one would get colder faster and stay below freezing longer. At least this is how I have obseved cooling so far since I have had my weather station. The morning of 1/26/07 was windy (until early morning) and quite dry with dew points as low as 30F. The air temp had stayed in the upper 40's to low 50's until the wind calmed early in the morning, the dew point stayed around 30-31F even when the wind calmed. Once the wind died way down, the bottom fell out and I went down to 39F from upper 40's in a matter of a couple of hours purly due to radiational cooling. This morning, a different story. No wind, completely clear from 12:00am on. I thought it was going to get just as cold as the previous night but the dew points stayed in the mid 40'sF all night. I bottomed out at 45.3F. The cooldown was slower and not to as low a level even though conditions were ripe for radiational cooling (clear skies no wind). The amount of moisture in the air is very important. I feel that during radiaitonal events, the more moisture in the air, the warmer it will stay.

[Alan_Tampa]

Frost?  What the hell is frost?  

Alan

[amazondk]

Forst normally forms in the freezer compartment of our frost free fridge if you leave the door open too long.  Aside from that it has become an alien idea around here.  But, when young in Montana frost was a regular part of daily life.  I think it would be hard to explain to people around here what a car window scrapper is.

dk

[Zac in NC]

(amazondk @ Jan. 27 2007,15:55)

QUOTE

I think it would be hard to explain to people around here what a car window scrapper is.

dk

Yeah, thats a terrible problem to have, Don. We have those things here.

Zac

[Kathryn]

When I talk about frost, I mean on my plants. Frost on my roof or car doesn't matter. So far no frost on palms this years.

Kathryn

[Neofolis]

The surface is very important.  I rarely see frosts in my garden, partly because it is so enclosed, but probably also because there is a heated polytunnel releasing some heat into the garden.  When I do see frost, the first place I see it is either on the concrete ground or on a plastic kids playhouse roof that is in the garden.  Because the frost will only form on a surface that is equal to or below the dewpoint temperature and below 0°C/32°F then the surface temperature of whatever is very important.  The surface temperature of the concrete at ground level is always colder than the leaf temperature even just a few inches above floor level by early morning.  Equally the plastic roof which is 3-4' above ground level is also colder.  Concrete and plastic are not good heat conductors and less prone to frost formation than metal or glass, but it would appear much more prone than foliage.

What is the point of determining if a plant is cold hardy or frost hardy if we are going to treat frost as anything other than frost on foliage.  Whilst I totally agree that in general terms people say that they have had a frost whenever there is a visible frost on any surface, that information is no help whatsoever in terms of knowing plant tolerances.  It's like someone in low elavation Hawai'i saying all my plants are totally frost hardy, of course they've never actually had any frost on them, but they have never been damaged by frost so they must be.

When I was plumbing for a living I would often have to use an electric pipe freezer which had metal paddles.  When the paddles got cold enough frost would form on them, despite the ambient temperature being above 20°C/68°F.  It obviously didn't make all of the plants in the room suddenly turn brown or defoliate, because they were not exposed to the frost.  I realise that is an extreme example, but if the frost is not on the plants it is not relavant to the plants' frost tolerance.

If we are going to determine frost tolerance and cold tolerance to be different properties of a plant then the frost has to be on the plant.  Otherwise it's like me saying all of the plants in my polytunnel were fine, despite there being a frost in the garden.

As frost can form at temperatures reasonably above 0°C/32°F, plants which have frost on them in these situations can be damaged, despite having survived frost free temperatures considerably lower without damage.  In such situations it is almost certain, in an otherwise healthy plant, that the frost has caused the damage.  If that frost had only formed on metal or glass surfaces, it is a fairly safe assumption that the plants would have been undamaged, so how can the two situations be compared equally.  Many people have also described how frost only formed on lower leaves of plants or on horizontal leaves and how these were the only leaves that were damaged, so again there is a correlation between visible frost causing damage only on the foliar sufaces on which it forms.

It would be interesting to compare damage caused by temperature alone, frost alone and the two combined.  I suspect that frost tolerant plants will survive lower temperatures when they have a covering of frost, due to the frost insulating them from the lower surrounding temperatures, but in plants not tolerant of frost the opposite should be true, that they would survive lower temperatures if they remained frost free.

[ruskinPalms]

I agree Neo. We should specify whether or not there was frost on plants in the garden. I still personally would report that I had a frost if I saw any anywhere, but I would also specify on what surfaces. Also, I tried to start a thread comparing frosts and freezes but it is making its way to the bottom of the board without response. I think good information comes out of debate.