winter cold event vs 9b/10a palms

[Walt]

Coconut palm on December 17, 2010. 

[Walt]

My coconut palm by December 29, 2010. My royal palm on December 29, 2010.

[kinzyjr]

16 minutes ago, Walt said:

Moving up to the morning of  December 15, 2010, you can see my bananas are toast. My coconut palm's fronds are severely burned. I even used a 30,000 BTU kerosene forced air heater to help protect the fronds. It made about as much difference as fart in a whirlwind -- when my low temperature dropped to 22.1 degree F that morning. This is why I gave up on trying to protect the fronds. I just concentrate on protecting the trunk and meristem.

22F in Sebring... Ouch!  I've heard you mention it before and seen the graphics, but it's just hard to fathom from my time going through there.  The lowest I've seen in my time here is 24F, and I'm a solid 1.5-2 hours northwest of you.  Even January 2010 bottomed off at 26F here.  As you've mentioned in other posts, there are other parts of Sebring that are warmer and support more tropical palms.  Outside of the more urban part of Lakeland, @JayW recorded 16.7F in 2010.  It's hard to believe less than 10 miles can drop you a full zone worth of temperatures, but it is Florida.

[RedRabbit]

1 hour ago, kinzyjr said:

22F in Sebring... Ouch!  I've heard you mention it before and seen the graphics, but it's just hard to fathom from my time going through there.  The lowest I've seen in my time here is 24F, and I'm a solid 1.5-2 hours northwest of you.  Even January 2010 bottomed off at 26F here.  As you've mentioned in other posts, there are other parts of Sebring that are warmer and support more tropical palms.  Outside of the more urban part of Lakeland, @JayW recorded 16.7F in 2010.  It's hard to believe less than 10 miles can drop you a full zone worth of temperatures, but it is Florida.

Florida does have some weird pockets that are warmer/colder than you'd logically expect. S. Tampa seems like it is a half zone colder than the same latitude in Pinellas County. Meanwhile portions of Sarasota County as far inland as I-75 seem to be solidly 10A... I'm sure there's a good reason in each case, but whatever it is it is too complicated for me to explain. 

[Sandy Loam]

It is wacky, isn't it?  I wish there were a map which showed all of these microclimates and extremes, complete with colour-coding by degree range too. The USDA maps are not specific enough and some people on PalmTalk disagree with them due to their generalities.

To me, the most shocking has been on those record cold mornings when, in real time at 7:00 am, I see a 40 degree (Fahrenheit) difference between Key West and Gainesville, where I live.  When it's 62 degrees in Key West and 21 degrees in Gainesville (approximately) simultaneously, it strikes me as astounding because that contrast is happening within a single state.  To find a similarly drastic temperature gap in Europe, you might have to go from the tip of the Mediterranean all the way up to Scandinavia.  That type of temperature contrast simply wouldn't be happening a short drive away. 

[Phoenikakias]

7 hours ago, Walt said:

 It made about as much difference as fart in a whirlwind --

 yet it is a very old word with origins in an ancient non written language which had been widespread directly or indirectly to whole Europe. Therefore there are cognates in other modern or ancient languages like perdzu (Lithuanian), perdet (Russian), pjeradh (Albanian) and pardate (Sanskrit).

[Walt]

One thing I realized quickly was that there was nothing monolithic about nighttime low temperatures in my county, on the coldest winter nights based on temperature readings taken from various temperature recording sites (personal weather stations on the Weather Underground network, as well as official sites, such as FAWN and Archbold Biological Station). I've actually seen a 20+ degree difference between the coldest reporting stations and the warmest reporting stations on the coldest radiational cooling nights.

I remember on February 14, 2006 the morning low was 26 degrees in the open at my place, but only 41 degrees at a friend's house (just 3 miles away) about 300 feet (and slightly uphill) from the east shore of Lake June). I also confirmed his temperature, as I had placed a Halsey-Taylor hi-lo thermometer on a vacant lot just down the road from my friend's house. This lot was owned by my parents at the time. I drove over to the lot that morning to see what the morning low was and to also reset the thermometer.

But that same morning Archbold Biological Station (8 miles south of Lake Placid) recorded 19 degrees!  ABS is the coldest spot in Highlands County, and you can see this area on the newest USDA cold hardiness map. Twice ABS has recorded a low of 13 degrees F (-10.45 C).

I've read that the soil in the ABS area radiates ground heat much faster than soils elsewhere in the county (on radiational cooling nights), and why it gets much colder there. Also, the Lake Wales Ridge (higher elevations always run much warmer due to rising warmer air and the air inversion layer). And the areas around the lakes receive the thermal benefit of the water (like coastal area do). 

Check out the 9a area (which is more often 8b) just south of Lake Placid on below temperature map: http://planthardiness.ars.usda.gov/phzmweb/interactivemap.aspx

 

 

 

[sonoranfans]

the long term survivability of royal palms south of tampa bay is near the 41.  I am 1.9 miles east of the 41.  Driving around, there are no visible royals east of my area but perhaps ~30 established at 25' or larger in my neighborhood that also survived 2010.  Basically, the distance from the water inland, which varies 3x for the 75 and much less so for the 41, is the best zone 10 marker.  The 75 is not a good marker for climate as its distance from the water varies so much.  In all this low temperature discussion we shouldn't lose the length of cold as it can be more important than the ultimate low.  this is because the temperature of the palm is more critical than the temperature of the air.  Air transfers heat/cold poorly, it takes time.  This is generally why radiational events are less damaging than advective events with similar temps, the length of exposure can be critical.  I saw a 21F radiational event in arizona where a 20' royal survived unprotected, though defoliated.  This particular advective cold burned the lower leaves of my copernicia baileyana, a solid 9B palm.  The damage in my yard is a little complicated by hurricane damage as quite a few of my palms had significant damage to 1/3 to 1/2 of their crowns in IRMA.  Damaged foliage may have led to more cold damage.   My 11' overall borassus A had 3/4 of its leaves burned, a solid 9B palm like the caryota mitis and the baileyana, with plenty of damage. As far as wrapping my palms for the cold, 25'-35' palms present a risk I am not willing to take.  I am not interested in falling off a ladder from that height.

[pj_orlando_z9b]

Great info Walt and others. I wrapped my coconut in January with C7 lights, burlap and layers of sheets. I lost near the entire crown but the trunk and meristem were in tact. I had secondary fungus challenges that lasted until May. The left is the day after the freeze (28F for 4 hours and freezing for 6 hours). They right pic is the palm on July 1. The last 2 spears have been normal (no wilting or deformation).

[pj_orlando_z9b]

Here was my simple form of protection. I realize I could have gone higher with the protection or even tied up the fronds.

Edited July 2, 2018 by pj_orlando_z9b

[Walt]

20 hours ago, sonoranfans said:

the long term survivability of royal palms south of tampa bay is near the 41.  I am 1.9 miles east of the 41.  Driving around, there are no visible royals east of my area but perhaps ~30 established at 25' or larger in my neighborhood that also survived 2010.  Basically, the distance from the water inland, which varies 3x for the 75 and much less so for the 41, is the best zone 10 marker.  The 75 is not a good marker for climate as its distance from the water varies so much.  In all this low temperature discussion we shouldn't lose the length of cold as it can be more important than the ultimate low.  this is because the temperature of the palm is more critical than the temperature of the air.  Air transfers heat/cold poorly, it takes time.  This is generally why radiational events are less damaging than advective events with similar temps, the length of exposure can be critical.  I saw a 21F radiational event in arizona where a 20' royal survived unprotected, though defoliated.  This particular advective cold burned the lower leaves of my copernicia baileyana, a solid 9B palm.  The damage in my yard is a little complicated by hurricane damage as quite a few of my palms had significant damage to 1/3 to 1/2 of their crowns in IRMA.  Damaged foliage may have led to more cold damage.   My 11' overall borassus A had 3/4 of its leaves burned, a solid 9B palm like the caryota mitis and the baileyana, with plenty of damage. As far as wrapping my palms for the cold, 25'-35' palms present a risk I am not willing to take.  I am not interested in falling off a ladder from that height.

I totally agree. In a typical radiational cooling event, the palm's core temperature is going to lag behind the ambient air temperature (at least to some degree), so at sun up, when (generally) the air temperature has dropped to its lowest (say 30 degrees), the meristem's temperature would be slightly higher. How much I can't say, but the laws of physics would dictate this. This would be especially true if the palm's trunk and meristem was wrapped with insulation, say in late afternoon the night before the freeze.

With respect to my coconut palm, I remove the insulation blankets during the day so that the trunk can be exposed to direct sunshine, absorbing the sun's radiation. The south side of my palm's trunk is noticeably warmer than the air temperature. I want to capture that heat, so before the sun goes down I recover the trunk and meristem with insulation blankets.

As far as trying to wrap tall palms, when that day comes with my coconut palm, nature will just have to take here course. Right now I could still wrap my palm with an 8-feet step ladder, but that's all the further I'm willing to go. 

One other point about radiational freezes, generally the coldest air is at ground level and then gets warmer with elevation. I found that air stratification layers vary in depth from one freeze to the next. Sometimes the depth of the cold air is deeper than other nights. But the point I'm making is, the taller the palm, the warmer it should be at the meristem.  My big Ficus altissima tree sometimes will get brown leaves up to a certain level, then the damage stops. Other times that line is much higher up the tree. Same with pothos vines I have growing 40-50 feet up some tall slash pines.

[Walt]

12 hours ago, pj_orlando_z9b said:

Here was my simple form of protection. I realize I could have gone higher with the protection or even tied up the fronds.

PJ. Yes, your protection probably saved your coconut palm. About all you can do is use more insulation in the areas you protected, not having exposed light bulbs where much of the heat is being lost. I think your coconut palm is now too big to even think about trying to bundle it, although bundling would help some, not doubt to help some of inner leaves, giving the palm more green for photosynthesis come spring.

[Walt]

Below is a photo I took in January of 2012. Note that I placed rags and towel remnants in the meristem area and over lower petioles before wrapping the heating cables over them. The rags prevent too much prolonged heat from damaging the tissue. I then wrapped over the cables with insulation blankets. Back in 2012 I could install this protection just standing on the ground. Now I need a step ladder. One caveat when using heating cables. Never overlap one over the other. The cable string cannot touch itself over the length of the cable, othewise they will melt together and short out at the point they touch. This won't happen right away, but over the course of a long night it will happen. I ruined a heating cable this way. The directions warns of this. Of course, these cables are intended to keep outdoor water pipes from freezing (when used with pipe insulation), but they work well for my purpose if one knows how to use them. I prefer heating cables over string lights because the heat is consistent all along the cable, not at just light bulb points. But I also use string lights, too.

[sonoranfans]

Walt, I took heat transfer as an engineering student so I do understand the delay between air and bud temps.  It will take longer for larger more insulated buds to drop to freezing, perhaps a few hours depending on how quickly temps drop.  For smaller palms and leaves, cells will rupture due to water expansion much more quickly.  There will be a temperature gradient from outside to inside the bud as it cools.  Air cools solids much more slowly than liquids so the length of a short radiational cold event is critical.  And yes cool air is more dense so it collects at the ground, leaving warmer air at greater heights.  For (windy) advective events, there is little or no difference in temps at the ground and at 20-30'.  So the radiational events may tend to be colder in ultimate lows in our area, but they are shorter in duration and tend to have warmer air at greater heights, making them more survivable for those larger palms.  Also advective events reduce the influence of nearby warm water by sweeping the radiated heat away in the wind.  

[kinzyjr]

@sonoranfans I definitely agree that US-41 is a much better separator for the coastal zone where you can grow more tropical stuff vs. the inland climate with more frequent frosts where you are better off dialing it back a notch.  Certainly, what you say about advective events was demonstrated by plant damage on my property.  I had more damage from this windy, advective freeze at 28F than I did with an ultimate low of 24F a few years ago with no wind and a fairly quick rebound above freezing.

You mentioned duration of cold as well.  Most of my area was below freezing for anywhere from 8-12 hours.  My memory says that my weather station recorded temperatures below freezing for ~10 hours.  Our airport recorded a record low for the day at 25F. 

This is a little write up in our paper about the freeze: http://www.theledger.com/news/20180118/polk-growers-pull-through-record-cold-crops-sustain-minimal-damage

[Walt]

On 7/3/2018, 11:24:14, sonoranfans said:

Walt, I took heat transfer as an engineering student so I do understand the delay between air and bud temps.  It will take longer for larger more insulated buds to drop to freezing, perhaps a few hours depending on how quickly temps drop.  For smaller palms and leaves, cells will rupture due to water expansion much more quickly.  There will be a temperature gradient from outside to inside the bud as it cools.  Air cools solids much more slowly than liquids so the length of a short radiational cold event is critical.  And yes cool air is more dense so it collects at the ground, leaving warmer air at greater heights.  For (windy) advective events, there is little or no difference in temps at the ground and at 20-30'.  So the radiational events may tend to be colder in ultimate lows in our area, but they are shorter in duration and tend to have warmer air at greater heights, making them more survivable for those larger palms.  Also advective events reduce the influence of nearby warm water by sweeping the radiated heat away in the wind.  

Tom,  having an understanding of heat transfer can definitely help one in protecting palms from cold and frost. Some people will wrap a palm's trunk with a blanket, but use no supplemental heat (i.e., string lights, heating cables). But that does very little to protect the trunk, since the trunk doesn't give off/generate heat, heat that would transfer out to the ambient air, but slowed down by the insulation wrap. The only heat a palm trunk would have at night to give off would be what it absorbed during the day. So, say the palm's trunk (from absorbing the sun's radiation and ambient air temperature during the day) was 50 degrees at sundown, wrapping the trunk at that time would help to slow down the heat transfer from the trunk to the colder ambient air (which would continue to drop at sundown).  So a wrapped trunk (under the above circumstances) would loss what little heat it had vis a vis an unwrapped trunk. But over the course of a long cold night, it would be that much of an advantage. But the same palm that was wrapped, but with string lights or heating cables, would fare much better. Heat always transferring from hot to cold (no exceptions), heat would always transfer to the palm's trunk, along with also transferring through the insulation wraps to the outside colder air. But the more insulation wraps, the better, and slower the heat transfer.

On some palms, when I use old flannel sheets for wraps, I usually have three layers of wraps. In any event, the wraps and heating cables work for my palms to keep them from being frozen. But now most, other than the coconut palm are too tall, and I wouldn't bother to try wrapping them. Too dangerous trying to wrap a palm off a 10 feet step ladder. And some of my palms can't even be accessed fully from a 10 feet step ladder.

[Walt]

Yesterday I decided to remove two coconuts from the oldest, bottom most bunch. I drained one of the nuts of water. I was shaking it and could hardly hear water sloshing around in the nut, so I did not know what to expect. However, the nut was almost full of water. Both nuts (even with husk) were on the small side. But I got maybe 6 ounces of water, and it was very sweet. I'm going to open the nut tonight. I placed the nut in the freezer overnight so that the meat will be easier to separate from the shell. Below are some photos I took. I also picked two pineapples (not ripe) because the raccoons have already started eating into them. These were good sized pineapples, and I used one for scale so as to show the size of the coconuts.

[Walt]

Glass of sweet coconut water.

[sonoranfans]

Looks good walt, maybe get some coconut creme pie with those nuts?  Yes, I certainly agree that active heating with cables and wrapping with insulation is way better than just insulation.  I have watched you care for those cocos for years, great to see them produce for you!  

[Walt]

1 hour ago, sonoranfans said:

Looks good walt, maybe get some coconut creme pie with those nuts?  Yes, I certainly agree that active heating with cables and wrapping with insulation is way better than just insulation.  I have watched you care for those cocos for years, great to see them produce for you!  

1 hour ago, sonoranfans said:

Looks good walt, maybe get some coconut creme pie with those nuts?  Yes, I certainly agree that active heating with cables and wrapping with insulation is way better than just insulation.  I have watched you care for those cocos for years, great to see them produce for you!  

Yes, I think I got my coconut palm about 14-15 years ago. It's gratifying to have it, and even more so when I propagated two new palms from it. My coconut palm surely would have been a goner had I not protected it with heating cables during the coldest winter nights. I guess my palm, growing much slower than other varieties, is beneficial to me as it allows me to protect it, albeit from a 6-feet step ladder now. Once I can't access it from an 8-feet step ladder I might have to figure on some other type of protection method, a method that would protect the trunk and meristem. I think that would take a 30K BTU forced air propane heater pointed at the base of the trunk, but with some kind of deflector to divert the warm air up along the trunk and into the canopy. In any event, I will cross that bridge when I come to it.

[Walt]

This evening I opened up my coconut. The meat wasn't as thick as it has been in past years, but it was just as sweet, maybe sweeter. I gave the other coconut to a friend, so I will have to ask him how his was. He is a distance neighbor that gave me the small coconut he found on Key Largo, which I posted a photo of earlier in this thread, so me giving him one of my coconuts was partial pay back. The coconut meat came out pretty much intact, but the pesky brittle inner nut coating didn't come off; sometimes it does, sometimes it doesn't. I don't know what the secret is.