Heating a backyard

[Tropicdoc]

Not sure which forum to post this in but.....

we are projected to hit 31 this week- first freeze of the year, might be the only one.

do y’all think that heating my pool can keep the area around it 1 degree warmer?

pool is 18 x 35 5 feet deep

or maybe just heat my 8 foot spa up to 100 for the night?

[AZPalms]

  On 1/27/2019 at 9:34 PM, Tropicdoc said:

Not sure which forum to post this in but.....

we are projected to hit 31 this week- first freeze of the year, might be the only one.

do y’all think that heating my pool can keep the area around it 1 degree warmer?

pool is 18 x 35 5 feet deep

or maybe just heat my 8 foot spa up to 100 for the night?

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Not sure if 1f will make much difference for your effort. What types of palms? Is the pool area enclosed? 

I had the unfortunate (fortunate for testing and learning lol) of 5 nights between 26-33f a few weeks back. I protected as best I could. Didn’t lose a single palm so far but some damaged and I have a pool as well. The palms near the pool and the ones in varying parts of the yard all exhibited similar damage and spotting on fronds. My point is, even if the pool helped a a degree or two, still at or below freezing. 

[Walt]

The pool won't help much because the heat transfer from the pool water out into the surrounding yard will be too slow and too little. About 15 years ago I had an above ground pool (25'x13'x4') and I had a double adonidia palm in a pot (the crowns  well above the rim of the pool) pushed right up against the pool to where part of the fronds were actually over the pool water. I had an overnight low well into the 20s, and both palm's foliage was damaged.

 Further, on one cold night I ventured outside by the pool with a digital pocket thermometer, and as I recall there was virtually little or no difference in air temperature standing next to the pool our a ways out from it.

But my pool wasn't heated. I don't recall what the water temperature was, certainly no higher than in the 50s. My pool was nominally around 10K gallons, and it would drop about 5 degrees overnight, typically. Doing the math, that's about 416,500 BTUs of heat loss. That's a relatively substantial amount of heat if it could be captured and directed to a smaller area. But figuring the ground area beneath the pool, all the side walls, plus the surface of the pool water (all radiating out heat from the water), and over the course of about 12 hours, it's not near enough heat to cover a large area and travel far beyond the pool.

That being said, had my pool water been 85 degrees and the ambient air temperature around it in the upper 20s, the heat transfer rate from the water would be much faster, and maybe the immediate air around it might be a degree or so higher (especially right above the water, rather than out to the sides), but still not enough to make much of a difference much too farther away.

[Really full garden]

I think it depends how much you can heat your pool and if there is little to no wind.

Have you thought about using those portable propane patio heaters ?They use them in Animal Kingdom.

[Tropicdoc]

Walt gave some good first hand info. I was thinking of bringing the water to 75 or so but most plants are 10 feet away from the water and I’m sure there will be a little wind. Yes I have thought of the patio heaters. They don’t run for long on a propane tank and I’m concerned with the fire hazard. Most winters we have several freezes so all this would not be worth it but since we may only have a single freeze thought I could spare some monstera and bananas from die back

[FishEyeAquaculture]

I think a bonfire using oak logs (think hot enough to burn 8”+ diameter logs) would not only be cheaper, but more effective. 

[PalmTreeDude]

If you are trying to protect a few plants from an occasional freeze in a small area,  you could get a small Smudge Pot. I know some citrus farmers use them when there is the threat of frost. 

[enigma99]

I prefer the large patio heaters -- 48,000 BTU ones. 3 of them will heat an entire backyard. For me, works great since I use them maybe once or twice per year.

[Missi]

  On 1/28/2019 at 2:24 AM, enigma99 said:

I prefer the large patio heaters -- 48,000 BTU ones. 3 of them will heat an entire backyard. For me, works great since I use them maybe once or twice per year.

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That's a great idea! Do you know if they're safe to run overnight? 

[Allen]

If the banana has overhead cover it probably won't hurt.  If really thick only the top leaves may burn.  Even a light frost may only burn it a bit.  The main pseudostems should be fine.

Edited January 28, 2019 by Allen

[Tropicdoc]

  On 1/28/2019 at 3:10 PM, Allen said:

If the banana has overhead cover it probably won't hurt.  If really thick only the top leaves may burn.  Even a light frost may only burn it a bit.  The main pseudostems should be fine.

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Yeah, actually been reading about bananas in zone 9 and most people cut them to the ground after freezing, but I'm gonna start leaving the pseudostem to maybe get more fruit after mild winters like this one. My monstera came back from 18 F last year! That's why this year I planted more. Not concerned with any palms. (Arenga engleri, Chamaedorea radicalis, Butia x Parajubaea, Beccariophoenix alfredii, Butia x Jubaea x Syagrus). Just that turning on my gas pool heater would be an easy thing to do, and was wondering if it would accomplish anything.

[Josue Diaz]

I agree with @enigma99, space heaters (or a fire pit) coupled with a fan to maintain air flow. Commercial citrus and avocado growers do that here and it appears to work for them. 

[DavidLee]

Honestly I don’t think it is worth the hassle. Last year at my location we dropped around that temperature. Our banana trees only showed minor damage without being covered. Maybe you can cover them with something. Heat from the ground will be enough.

[kurt decker]

 I always use overhead water. Anytime it gets under 40°, I turn the water on the sensitive stuff. The water coming out of the ground is never less than 70 degrees. So throwing a constant 70 degrees into the air around the plants certainly gets it up a critical 4 to 5 degrees. I put cheap waterproof thermometers all over the place  and watch the temps. It's a wet and cold job,  but you'll be glad you did it. You definitely get  a nice boost from that. This also prevents desiccation from cold drying winds, which destroy tropical plants. At freezing, the dynamics change a little bit, your plants will get coated with ice, but it still seems to be very helpful. I've never had a hard freeze in my Nursery. I've seen a lot of pictures from 1989, Jeff Searle and Gary Zill, with icicles hanging all over their plants. Good luck

[Zeeth]

  On 1/28/2019 at 8:05 PM, kurt decker said:

 I always use overhead water. Anytime it gets under 40°, I turn the water on the sensitive stuff. The water coming out of the ground is never less than 70 degrees. So throwing a constant 70 degrees into the air around the plants certainly gets it up a critical 4 to 5 degrees. I put cheap waterproof thermometers all over the place  and watch the temps. It's a wet and cold job,  but you'll be glad you did it. You definitely get  a nice boost from that. This also prevents desiccation from cold drying winds, which destroy tropical plants. At freezing, the dynamics change a little bit, your plants will get coated with ice, but it still seems to be very helpful. I've never had a hard freeze in my Nursery. I've seen a lot of pictures from 1989, Jeff Searle and Gary Zill, with icicles hanging all over their plants. Good luck

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Would this have any benefit for taller palms outside the reach of sprinklers?

[kurt decker]

It could. Heat rises. You can see the steam rolling up above the sprinklers. And you could always point a Rainbird skyward if you wanted to get better coverage. That said, the coldest temperatures, and the most tender plants always seem to be at ground level. So that's the stuff I try to protect.

[Merlyn]

Depending on the type of bananas you have, some might not mind temperatures near (or even below) freezing.  I have quite a few bananas that I planted to provide "instant shade" after cutting down the water oak canopy.  Some I should have planted earlier in the summer so they'd have more psuedostem before winter.  I've had two nights just barely above freezing, one measured 33-34F for 4 hours with leaf surface temperatures (optical) around 29-30F, and another in mid-December at an estimated 35F.  Most bananas showed little damage, the "Dwarf Cavendish" and "Red Abyssinian" from Lowes had minor frond yellow burn.  A Bordelon had significant damage but seems okay, part of the damage was from a bear tromping around and munching some of my white bird of paradise.  Three "Siam Ruby" were defoliated and died, but they weren't all that happy beforehand.  Undamaged ones that still grow (but slowly) in the last 2 months are Dwarf Red, Saba, Basjoo, Zebrina, Little Prince, Truly Tiny, Lasiocarpa, Kandarian, Thai Black, Sumatrana X Cross, Ice Cream, Goldfinger and a couple of Mekong Giant seedlings.  All were unprotected, all without significant canopy.  Most of them are under 2 feet tall because I planted them in October-November and were just starting to grow when the first cold front hit in December.

[NC_Palms]

I also agree with @enigma99, I would consider getting a patio heater. I've been considering getting for quite some time but it's cheaper for me just to use lights and towels for protection. 

[Tropicdoc]

  On 1/28/2019 at 8:05 PM, kurt decker said:

 I always use overhead water. Anytime it gets under 40°, I turn the water on the sensitive stuff. The water coming out of the ground is never less than 70 degrees. So throwing a constant 70 degrees into the air around the plants certainly gets it up a critical 4 to 5 degrees. I put cheap waterproof thermometers all over the place  and watch the temps. It's a wet and cold job,  but you'll be glad you did it. You definitely get  a nice boost from that. This also prevents desiccation from cold drying winds, which destroy tropical plants. At freezing, the dynamics change a little bit, your plants will get coated with ice, but it still seems to be very helpful. I've never had a hard freeze in my Nursery. I've seen a lot of pictures from 1989, Jeff Searle and Gary Zill, with icicles hanging all over their plants. Good luck

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Interesting, I have a probably 50 x 50 foot area all under a live oak that is my "jungle". Irrigation lines are cheap Mister Landscaper ones from Lowes run through the underbrush and with heads all around. The irrigation is hardly ever used because of our high rainfall. But...…………. what if irrigation was run up the oak tree and then fine mist was projected downward...….. how much temp gain would I get on a cold night? Would that mist of tap water damage my palms if used too much in an overhead watering situation.

[RJ]

  On 1/28/2019 at 9:29 PM, Tropicdoc said:

Interesting, I have a probably 50 x 50 foot area all under a live oak that is my "jungle". Irrigation lines are cheap Mister Landscaper ones from Lowes run through the underbrush and with heads all around. The irrigation is hardly ever used because of our high rainfall. But...…………. what if irrigation was run up the oak tree and then fine mist was projected downward...….. how much temp gain would I get on a cold night? Would that mist of tap water damage my palms if used too much in an overhead watering situation.

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I would think a fine mist would cool before it hit the ground and loose the benefit of the warm water. Perhaps the zone 4b is coming out in me 

Edited January 28, 2019 by RJ

[Walt]

If one knows the proper use of water, it can be one of the best methods for raising ambient air temperature on radiational cooling nights (clear sky, no wind).

If it's sunny out the during the day before the night of the freeze, I will saturate the ground with my 75 degree well water all around palms I want to protect. The saturated ground will absorb and hold more of the sun's radiant heat so that it will be released back into the air that night. I've read in University of Florida literature that if you saturate the ground enough during a sunny day it can keep nighttime air temperatures about two degrees higher than if you didn't saturate the soil. 

Also, I have ixora super king shrubs (zone 10 plants) planted along the south and east sides of my house. My roof shingles heat up during the day (when sunny). I will spray my roof with a garden hose and allow the water to absorb the roof shingle heat, and it runs off the roof onto my ixora shrubs and saturates the ground with warm water. I will wait for 30 minutes or so, then spray the roof again (as the shingles warm back up from the sun's radiant heat) and repeat the spraying process. I usually do this several times, stopping in time for all the foliage on my ixora shrubs to dry out before nightfall, but the soil all around them is saturated with water that can release heat at night. This extra heat helps at night to mitigate foliage damage.

Several times at night I will go out and re saturate the soil around my coconut palm, so that the heat from the water rises up into the fronds. This adds more heat to the soil to be released upward. Water has a decent heat capacity, and spaying it all around a palm can better evenly spread the heat.

It takes 1 BTU of heat to raise one pound of water one degree F. Conversely, it takes the removing of 1 BTU of heat to reduce the temperature of one pound of water one degree F.

So doing the math, if you were to spray 5 gallons of water (and water weighs 8.33 pounds/gallon) onto your soil, and assume the water was 75 degrees F -- if that water cooled down to 32 degrees it would release approximately 1,790 BTU of heat. And if that same water were to freeze from 32 degree water to 32 degree ice, it would release an additional 144 BTU/pound (due to change of state latent heat of fusion), which would be an additional 5,997 BTU of heat. That would be a total of 7,787 BTUs of heat from five gallons of 75 degree water.

So, what if you then sprayed out 50 gallons of 75 degree well water. That would theoretically release (if all the water froze) 389,380 BTU of heat into your yard.

That's how I use water. I've never used water using a sprinkler so that it sprays and freezes on palm/shrub foliage because that requires the water to run constantly until the sun comes up and the air temperature to rise above freezing. If you just run the sprinkler until the foliage is covered with water, then turn the water off, the ice that forms on the foliage initially releases it's latent heat, but then, without more water to coat the ice (and release more latent heat) the ice will drop from 32 degrees and eventually drop to what ever the air temperature is. 

One problem I did have with spraying the soil around palms I want to protect is getting water on the trunk bases, and this water froze and damaged the trunk. This happened to an adonidia palm and A. alexandrae palm. That's why you have to use water cautiously.

Also, overhead watering all night, letting the water freeze on foliage and keeping the ice temperature at 32 degrees, eventually the ice build up gets too heavy and can start breaking branches, fronds, leaves, etc.

 

[Tracy]

  On 1/28/2019 at 8:05 PM, kurt decker said:

The water coming out of the ground is never less than 70 degrees. So throwing a constant 70 degrees into the air around the plants certainly gets it up a critical 4 to 5 degrees. I put cheap waterproof thermometers all over the place  and watch the temps.

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When I read 70 degrees it just didn't sound right to me based on my experiences, so I decided to look it up.  If you are interested there is plenty of information on what drives groundwater temperatures, but suffice it to say, it does vary depending on where you are located.  I found a nice map of the US and I would guess that looking at groundwater associations in other countries (membership is often well drillers or others with commercial interests in groundwater), you might find some similar maps.  In my region we are close to the 67 degree isobar but between it and the 62 degree isobar.  So you might want to check your water temps since it's easy and I'm sure you have a pool thermometer.  The benefits of using water are still there, just diminished as the water temps drop (see Walt's excellent physics lesson on btu's above).

 

[Walt]

  On 1/29/2019 at 2:07 PM, Tracy said:

When I read 70 degrees it just didn't sound right to me based on my experiences, so I decided to look it up.  If you are interested there is plenty of information on what drives groundwater temperatures, but suffice it to say, it does vary depending on where you are located.  I found a nice map of the US and I would guess that looking at groundwater associations in other countries (membership is often well drillers or others with commercial interests in groundwater), you might find some similar maps.  In my region we are close to the 67 degree isobar but between it and the 62 degree isobar.  So you might want to check your water temps since it's easy and I'm sure you have a pool thermometer.  The benefits of using water are still there, just diminished as the water temps drop (see Walt's excellent physics lesson on btu's above).

 

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Well, your map confirms what I've always been told that the ground water in my area is around 75 degrees -- as I'm located about mid way between the 72 degree and 77 degree temperature lines. And regardless of 10 -15 degree ground water temperature difference, the bulk of the BTUs released comes when the water changes state to ice (where 144 BTUs/pound of water is released) -- so water, even tap water could benefit gardeners as freeze protection -- within limits, of course.. 

It's funny how temperature is relative. When it's 90+ degrees in the summertime my ground water feels cool when it touches my hands. Conversely, in the winter when I go out at night and the temperature is in the low 30s and I spray well water around my coconut palm -- the water feels warm on my cold hands.

I have a digital pocket thermometer that reads in tenths of a degree, plus I have a thermocouple, and when I water I can see the air temperature rising above the ground due to the well water I sprayed on the ground.

[BS Man about Palms]

Walt, I've said that for a while, I like how you put it more scientifically.

 

[Tropicdoc]

Well, Polar vortex never got here, so, never mind.. Coldest weather on record for the Midwest, and we didn't even freeze. Everything still green. Weird. 10A winter here...…….. so far.