Frost Protection

There’s a lot of collective wisdom on this forum, so I’d like to get some thoughts on an idea of frost protection, possibly for a commercial orchard, or a large backyard orchard.

I’ve been reading a lot about frost protection lately and not seen anyone try anything like this.

Several weeks ago I ran across an article about a new airblast heater being sold in the U.S. (I can’t find the article now.) Anyway the inventors claimed the heater would provide frost protection for up to 10 acres. Basically one just hooks this big forced air heater to their tractor and tows it around the orchard all night, until the danger of frost is over. It’s like an airblast sprayer, but instead of spraying chemicals, it blows heat. Produces 1.7 mil. btu.

At first I kind of thought this wouldn’t work because as soon as you heat the blooms up, they will cool right back down as you drive past. However, after further thought, I’m wondering if these things might work.

From what I read, the amount of time blooms stay at sub-freezing temperatures is critical to their survival rate. Long periods of sub-freezing = dead blooms. Short periods, not so much. Plus I think actual frost on the blooms is worse, than cold w/ no frost. The reason I think this is because some growers spray a low dose of copper on the blooms to kill ice nucleating bacteria (Kocide is labeled for this.)

A pull behind airblast heater wouldn’t heat the whole orchard, but would reduce the length of time the blooms sustained continued sub-freezing weather. Perhaps it would be akin to getting ones hands warmed up occasionally in cold weather (although I know humans are warm blooded and plants aren’t).

Plus I’m thinking a mobile heater wouldn’t allow frost to form on blooms, but I don’t know.

Anyway, my idea is that since I can’t afford a $20K+ pull behind heater like this:

What if I person used one or two of those salamander/torpedo forced air heaters? I have a 3 pt. platform I can mount behind my tractor, which I could put my small portable generator to run a couple of these type salamander heaters (400k btu).

They rent these type heaters around here for about 30 bucks a day, although they aren’t as big as the one linked above. If I remember right, it seems like these types of heaters would throw heat a pretty good distance, but it’s been a long time since I’ve warmed myself with one of them.

Basically the thought would be to drive around most of the night heating the trees up w/ kerosene salamander heaters instead of a big airblast heater. I wonder if something similar could work for large backyard orchards (pull a heater around w/ a small generator in a cart w/ a lawn mower.) Or if a person just had a few trees which couldn’t be covered (because of wind, or too tall) maybe rent one of these as a sort of stationary heater and let it run all night w/ extension cords. This may be a completely ridiculous idea, but I’m trying all kinds of things, and would like your thoughts.

This morning we were at risk of a frost event, and for the last couple days I’ve been building wood piles throughout the orchard. This morning at 4 a.m, I lit them (35 piles) to try to heat the orchard (sort of like a poor man’s smudge pots). It turned out it wouldn’t have been a frost damaging event, but I didn’t know that until after the fact. It was very labor intensive, and took a lot of wood, so I don’t know if I’ll do that anymore.

Accuweather is suggesting there is another possible frost damaging event for this Thurs. here.


I like the idea of the heat but what about a geo thermal sprinkler system that rotated around the orchard on a timer? Sector one sprayed on the hour , sector two 15 after, sector 3 30 after, sector 4 15 until the hour, as an example. The problem is with driving the orchard the fuel gets expensive and speed driven would factor into how effective the treatment was. If the water you sprayed was at 50-70 degrees the trees would be getting watered and frost protection at the same time.

Weather factors would be important: primarily wind speed, dew point, and height/strength of any inversion layer. A really strong inversion would help trap the applied heat nearer the tree.

The pull around heater would be effective on my orchard. It’s just a matter of how big an area it could heat enough to make a difference. 10 acres sounds like too much area for one heat source. I don’t have any way to calculate the rate of heat loss compared to heater output.

I think they have systems burning something like natural gas near each tree. Sort of like a bunson burner per tree.

The intermittent sprinkler plan is probably not a good idea. Water can and does rob heat as it evaporates. So the water would be stealing heat from the trees in between applications. Where that is used they stress continuous application of water until all ice melts.


I found this site.I just did a cursory reading and am not sure if their machines will work in every location.The only money figures I noticed were $3000-$8000. Brady

Wind machines are used by many of the commercial peach orchards and vineyards in NC. I believe the growers lease these machines. From what I understand, they work well during a frost event but not during a hard freeze.

Good to know Fruitnut I sprayed pumpkins with water after a frost several times to save them a few years ago when I planted in February. Best pumpkin crop I’ve ever raised and we are still eating them. At the time it was working me hard to spray them with water in the dark and I considered an automatic sprinkler. Every thing not sprayed died from frost. That was a light frost and pumpkins are not fruit trees. It was one large area and I sprayed them until sun up row by row.


With enough water and a light frost I could see that working. It’s like anything, with enough ammo one can over power most anything.

1 Like

this actually sounds like a p.bad idea, driving around at night towing a bomb basically, however it would definitely be fun.

My advice would be to do trial plantings on crops with more cold tolerance (or, varieties less susceptible to loss from frost). Probably not the advice you’re looking for :slightly_smiling:

So either try varieties more resistant to frost damage or plant a different crop entirely.

Fig, persimmon, pawpaw. Those are my top recommended fruits.

Then you change the kind of work you need to do. Driving around spraying heat all night seems like effectiveness would vary a lot across climates which would be frustrating, it’d be a lot of work, expensive, and with 1 lost battle you lose the crop even if you saved it the first 6 nights.

Fig, persimmmon, pawpaw specifically the work is more in marketing them. Experiment and find what works, then expand. At least for the small commercial grower there is an advantage in that it should be easier to find or create a niche market. Sell at the roadside, u-pick, or selling locally - it’s easier to sell 1 acre of figs than 100 acres worth of figs.

I know that’s not the right advice for every grower though, it’s maybe a bit more for the entrepreneur grower.

1 Like

I came across an interesting article from University of Florida that suggested its possible to gain 2 or 3 degrees on blueberries by just saturating the ground with water before the freeze. After lots of rain I have some standing water my the blueberry field and several 20 degree days coming so I get to test this idea. Also interesting that rabbiteye are more sensitive to a given temperature than highbush.

Water saturated soil provides some improvement on tree fruit too, but I’m not sure how much.

With some peaches in full bloom, and a very wet field I get to see what happens to my peaches when the temperature hits two 20 degree nights this week.


I hope your trees and blueberries come through. Are all your peaches in full bloom by now? I know if the weather is warm, they can open pretty fast.

When I originally started this thread 3 years ago I was still trying all kinds of methods for frost protection. I’m at the point I don’t think anything works to protect much, except overhead sprinklers and large frost protection fans (both of which I’ve never tried - too expensive for my small operation).

I think the copper spray just before bloom may have helped some, but I’ve not tried it as a controlled experiment. Just sprayed the whole orchard.

I’m trying something new this year, since most of my trees are in full
bloom but with very little foliage. We’re going to have lows of 26 tonight and 27 tomorrow night, and I plan on spraying KDL this morning and again this afternoon. This worked last year, but since the trees have so little foliage, I’m wondering how the KDL is going to get absorbed into the trees. Will flowers be able to do that? IDK so for extra protection I plan on placing a number of electric space heaters throughout the orchard in spots where the trees are fairly close together and running them all night. Since I only have so many heaters, some areas will have to fend for themselves. I should be able to tell, if the heaters helped or not.
We’ve had lots of rain lately, so the trees are well hydrated, which is one of the things you’re supposed to do before using KDL. I know some of you guys are not sold on KDL, but it sure worked for me last year.



Thanks for responding.

Fortunately, just one variety of peaches in full bloom but other varieties are close and the blueberries are a risk too.

I see many people here are trying a lot of different things depending on the size of their orchard and resources. If I had a pond, I would try some overhead irrigation but since I don’t I’m stuck. I tried the copper for ice nucleation bacteria on peaches which seemed to help, but I’m not sure. I sprayed copper a little later this year just in case it provides some benefit.

The UFL article is the only professional resource I have seen that suggested its possible to get a 2 to 3 degree boost just from water saturated soil. I hope its true!

After wading through a lot of info in that publication its interesting to learn that its normal for grass between the rows to get crunchy when you walk on it after a frost from just 36 degrees, so no more worries from crunchy grass.

I had heard a thermometer in a orchard read about 2 degrees low without a protective enclosure during a freeze but I had not seen that in writing either before that article. I built something similar to a “stevenson screen” box from scrap materials for my orchard thermometer so I can now determine the actual temp in the orchard. Edit: Here is a picture of an expensive professional version: Metcheck M11 Standard Size Stevenson Screen

The prediction is for 21 tonight and 24 tomorrow night so I’m expecting damage. We had two nights last year in the low 20’s and I had the best peach crop I have even seen, so hoping for the best.



Have you tried doing a bit of a controlled study? I know I never did when I used KDL. Bob Purvis never did either. I know we talked before of spraying half the trees with KDL and leaving the other half unsprayed (on my end). But I wonder if you have ever tried that?

Perhaps just spray one side of the trees and leave the other side unsprayed?

I’ve had full crops at 26F, and lost most of the crop at that temp at different times. In fact without checking my notes, I think it’s even been a tad colder at full bloom and had some crop without any protection.

As we have discussed in the past, part of the reason of my strong skepticism of the product is that it didn’t seem to work for me (again based only on anecdotal trials). I didn’t use it according to the current recommendations, but used it according to the manufacturer recommendations at the time, when they were still making strong claims about its effectiveness with their directions at that time.

Last Dec. when I went to the MI fruit expo, there was a talk about frost protection. The researcher said spray on frost protectants don’t work. That wasn’t the first time I’d heard a researcher claim that. It does tend to reinforce my anecdotal experience.

I think the copper spray may have some validity because there is no claim it will provide anti-freeze inside the flower. Instead the claim for copper is to kill ice nucleating bacteria, which has been tested. But again I’ve not tested that in a controlled study either.

How far are your peach trees along (bloomwise)

I think one year I had some trees blooming and other close when it got down to 22F. I had the crunchy grass with lots of frost on the blooms and thought I’d lost everything, but it turned out OK.

1 Like

Since I don’t have a large orchard, I want to try to get all of the
fruit I can get. If I’m going to spray a tree, I’m going to spray the
whole tree. My idea of the controlled study is if the heaters are
going to make a difference. I just hope I don’t blow any fuses.
All of my stone fruit, except peaches are in full bloom, with some
at shuck split. The peaches are only in light bloom, but mostly
still dormant, so they should survive and bear a full crop. Last year,
this freeze happened a week later than now and everything was much further along.
I know the “experts” doubt KDL, but It sure worked for me last year.
The first year I used it with marginal results, but afterwards, had a number of conversations with the KDL expert at AgriPro, who gave me a lot of tips on how to properly use the product. But we’ll see.
I hope I can post pictures like I did last year.

1 Like

I met a man that had a orchard in Ohio,
This was in gently rolling terrain .
We talked about frost protection.
He said he would take 2 bails of hay , lay them on the ground ,touching each other at the ends, light each end on fire ,and pour several gallons of water (2-3? I forget )in the middle of the hay. He said he just wanted them to smolder and create a fog ( steam from the water) I remember him bragging about how long they would smolder, if the water was just right.
He said this only worked if there was a low inversion layer , such that when the smoke went up, it pancaked out sideways.
If it did after lighting the first one , he would set more throughout the orchard.
He seamed sure this worked , " sometimes"
I have never tried it.

1 Like

That’s true, it only works if there is an inversion. If it’s windy, just like with smudge pots, it’s pointless. Researchers claim that if there is too much heat off a big fire, it can actually break through the inversion layer and cause all the heat to escape, even ground heat, and make things worse.

Here’s something you might think is funny Hillbilly. When I started to read the first few lines of your last post, I thought you were going to share some poem. It kind of started out that way.

Here’s how I’d finish your poem:

I met a man that had a orchard in Ohio
This was in gently rolling terrain .
We talked about frost protection
And couldn’t stop beating out our brains


I often think in rymes, but iam not very poetic

Without a good controlled study it’s impossible to tell if these things work. I’ve probably seen more damaging freezes in west Texas than almost anyone. We average several a yr. We’ve already had several this yr. It’s unusual to have one freeze take out 100% of the crop. Mid 20s freezes don’t normally take everything and may just be a mild thinning. And that’s at full bloom. When there are unopened blossoms it has to get really cold to take out everything.

The worst freeze I ever had was 13F two nights in a row at full bloom on peaches. I still got a few fruit, 5-10 per tree but that’s not 100% loss. That was mid March in Amarillo.