I've posted this the last couple of years but I'll put it up again. I'm curious if anyone else has tried it? Tell us if it worked for you.
Frost Candle
I'll share my little invention that I use in my citrus. I start with a jar candle, the little ones that are on restaurant tables sometimes. The one's I use are about 2 1/2 inches across and 2 1/2 inches tall. Next I take a 1 pound coffee can with one end out, the regular way you open a coffee can. Then I punch several holes in the sides. I'd say about 6 near the top and 6 two thirds of the way down. This is with the open end as the bottom so it can sit over the candle. I use a standard punch, making each hole about the size of a pea. You can stick a short 2x4 piece of lumber in the can to keep it from bending while you punch it.
I set these out, with a little stick, maybe the size of a pencil, under one side, so that the can is tipped. This lets air into the can for the candle.The cans do a couple of things. First, when it's below 30 degrees out, the candle wax will be so cold that the wick will burn a tunnel right down through the candle and most of the wax won't melt and burn. So the can keeps enough heat in that the wax can melt and the candle burns the way it should. Next they act as little radiators. The idea here is to heat a lot of air just a little. (The heat from a candle by it's self would all just go straight up and not help the tree.) They also keep the candle from blowing out in a light breeze.
I do this with about 80 candles for 100 citrus trees. Of course being out at 2:00 in the morning, freezing my fingers, lighting candles, is not a lot of fun, but it is a rather pretty sight when they are all going. My version of a Christmas tree, citrus and the fruit are the ornaments.
Be careful for fire hazard.
Do not place on or near mulch, branches, or other flammables. Clear a spot down to bare soil so that they are clear of any material that can burn.
Do NOT put these directly under the tree as that will be to much head and will "burn" them. I place them 3 to 4 feet out away from the tree.
If you do this, you should monitor them closely. I will put a movie on, make hot tea, set a timer, and check them once per hour after I have them set. or sometimes I just nap for an hour with the alarm clock to get me up and check.
I got all my citrus through the nasty hard freeze 2 years ago. We had 3 days of more than 12 hours of below freezing temps with a low of 10! one day and 2 more days with lows of 12. Sustained frost lasted for more than 12 hours. Nasty cold for citrus. The limes didn't fruit that year. The trees were ok though. Everything else had fruit (see my page for a list of everything we have.)
I also run irrigation water while doing this. the heat from the water helps too. Start irrigation water early, several hours before the temp drops below freezing, to build heat in
that area. If you wait until it starts to freeze, it's to late. I start candles about 2 hours or more before temps drop below freezing. I bought my first jar candles at Costco some while back but don't see them there any more. I
bought a few more this year at the dollar store and I buy wax and wick to refill my jars, much cheaper than buying new jar candles. For cans, check out the size of a 1 pound coffee can in the store, you can buy anything that uses the similar size can. I think some juices, like grapefruit juice, come in that size. Be cautious though of cans that have a plastic coating on the inside as the plastic will burn and the fumes are toxic. If you have friends who work in an office that has a coffee pot you could ask them to save cans for you. Also Mom's with kids in school often save things for crafts and might be a place to get help finding some. The one pound coffee can is just about the perfect size though, to use with a 2 1/2" wide by 2 1/2" tall jar candle though, so try to find cans about that size. That size jar candle should give you about 2 or 3 nights depending on how long you need to keep them going.
Remember, frost will last a little past sunrise, so don't put them out to quickly.
Also to blow them out, I use a cardboard or piece of wood about the size of a pizza box and just fan them out. They are too hot to pick up and that's too much bending over otherwise.
I don't like kerosene lanterns because they really are too hot causing the heat to rise in a column instead of radiating and heating a large volume of air just a little. The concept of smudge pots was to create rising air which would in turn cause air to flow through the citrus, not to directly heat the air, which is why they really don't work. Kerosene lanterns are also harder to work with, and much more of a fire hazard.

Softmentor, I've read some of your posts before and your gardening sounds fantastic. I can see how Christmas lights would not be practical for you (too many trees?), and being outside all night long watching candles would not be practical for me (work+school+family=no rest), but I think your method is outstanding, and I agree that it would look visually striking as well. I don't know if you get the amount of wind that we get here (upper Mojave Desert, Ridgecrest), but it can gust 20-30 mph for days on end it seems like (although when the weather is poor, it's usually warmer). I think at some point I will expand the garden patio into a green house that has wall panels that can be removed -- sort of a gazebo in the summer, and a greenhouse in the winter kind of plan -- and I'll use something with "fire" as a heat source then, or what I'd rather use: solar. I would love to sit in the patio/green house in the early spring and be in with those citrus blossoms, sipping coffee. Before I planted my first 2 mandarins, they bloomed while they were in the house. It was quite a surprise getting up in the dark early morning, and wondering -- "Gosh, what's that wonderful smell?"

And much thanks for the detailed reply.

Kev.

I have a key lime (and a pineapple!) planted in the ground. Key lime has a heap of mulch 1 foot deep around the bottom and 2 strands of globe xmas lights on it (total 130 watts) which are on 24/7 starting in late October. The trunk is wrapped in plastic. The bulk of the tree has a large plastic yard back over it. This is winter #2 for "limey" in the ground, here in southeast virginia.

I have a eureka lemon and a thompson grapefruit which reside in the garage. They will go in the ground in the spring and will get similar treatment.

Wow softmentor, I admire your effort! Very neat. Here in so cal we don't have to do anything in the winter, so we're very spoiled. You all have to work so hard in the colder climates, you deserve our respect. Have you ever tried to photograph the trees with their candles, maybe just as the sun comes up? Would love to see that!

I for one would also like to see all those trees from Softmentor with the candles lit and I'm sure many others on this site would also. That kind of work takes real dedication. I just have one little Navel Orange tree, in the ground 8 months. I had no idea what I was going to do with it in the winter, but I had some extra T-posts and Plexiglas laying around so I just put this makeshift greenhouse together. It already had an underground irrigation line from a previous tree years ago. I'll try it out first with a 60W bulb and thermometer. All this for an Orange?

{{gwi:641806}}
{{gwi:641808}}

Kevin, I did something similar to what you did with the Christmas lights...see pic below

Softmentor, wow...that would be really cool to see some pictures!

Norwood, what a great little set-up you got going!! That's such a great idea!

Unfortunately, I live in a deed restriction, the candle thing would not go over well with the HOA, lol...I have a few (young) Mango/Lychee trees that I just planted spring of 07...What I did was get some of the med/heavy grade frost cloth, which I ordered on the internet(all I could get locally was very thin), my DH built a small frame from 1/4" conduit from H. Depot. I strung Christmas lights C-7's(like Kevin did) on the trunk and laid them on the soil, to keep the soil warm...and covered them with the frost cloth. I live in Central FL, we do get a few days of freeze here, not often(thank goodness!)For what its worth, from what I've read you have to make sure the cover goes all the way down to the ground, to retain the heat inside(keep it from escaping).

Here is what mine looked like...Good luck with everyones trees...

{{gwi:563739}}

Here is what it looked like at night...
{{gwi:641811}}

puglvr1: your setup looks almost identical to what I did for a few years. I had some major and disappointing leaf loss year before last, and I don't know if it was because of the cold, or because of the heat; January has some days in the 70s here with lots of sun, and it can get to be 110deg inside the little individual green house. Picking the fruit was also difficult through the sides...and we get some serious wind as well that can last for days, and that tends to beat up the plastic pretty badly.

My pallet wrap idea looks odd, but it sticks on pretty well (with the help of some tape or a stapler) and it's disposable, and with a arm sized hole at the top or the bottom, I can reach in and pick fruit...sort of.

I wrapped some lights around the trunk and put bubble wrap over that for extra insulation, then just spun the wrap around the tree with the lights on it already. I might add a 3rd string to each tree this year just in case.

I wish I had a thermostat for each tree, but it's too much $ for me right now. My next big leap in tech is to use a 24v thermostat to control a semiconductor triac that will switch up to 40A (I'd have to do the math on 3 strings of 25 lights @ 4W X 5 trees, maybe 1500W or about 13A ?) Too expensive to leave on all of the time.

I need to get things going soon, it's dipping down into the 30s now.

I had some remote thermometers on them last year which I finally looked at. The low temp was 25, so it got down to the threshold of too-cold for sure. I'm pretty sure we had temps in the teens several times here, but I didn't have a 2nd thermometer with a hi/low memory to compare with.

Use 3/4 inch PVC pipe (plus fittings) to build a sturdy frame like a small greenhouse. PVC is cheap. Cover with poly sheetings, also cheap. Build a heater from a 5 gallon metal paint bucket covering a spotlight or heat lamp. It will heat the bucket, protect the light from condensation which could drop and break on a hot bulb and blcok out the light. The little "heater" is great for small spaces.

That's a great pic from pugivr1 at night. What kind of lights did you use? If my 60W bulb doesn't work I think I'll try tsmith2579's idea with the paint bucket and a spot light. The down side to my "Greenhouse" is having to water strictly with the irrigation because of the Plexiglas. Any idea what would make a few of the newer larger leaves start to curl up on the sides? Would it help to drill holes in the sides of the paint bucket for extra heat distribution?

you might try 35 gallons of water too, in your region that much give you the heat you need to make it though the cold nights.....

Norwood, Thanks!! I used C-7's 25 cnt clear Christmas lights per tree. They were 5 watts per bulb...total of 125 watts per tree. Like I said its very important that the frost cloth go all the way down to the ground to retain the heat inside. I wrapped a few of the strand on the trunk and the rest I laid on the bottom of the dirt.

Tsmith, where can you find a 5 gallon "Metal" paint bucket? All I ever see (I have one) is Plastic...that's a great idea though! Thanks...

I've thought about possibly placing my gas grill in between two of my citrus trees and keeping it on really low all night for the next really hard or prolonged freeze.

Either that or starting a fire in a fire pit or something.

My other thought would be to use some of those hand-warmers.

The last couple years we have only had light freezes, so I have not done anything outside of throwing an old sheet over to keep off the light frost.

OK, -smiles his jolly smile- I'll try to get some pics of my frost candles next time I need to run them.
Kev, checking your math, by the time you are up to 1500 watts, you can use a little space heater and they already have a thermostat. Just run a small fan on low to keep the warm air circulating in the contained area.
To cover large areas with more than one tree you can make a temporary green house very cheaply using PVC pipe for a frame and clear plastic sheeting. Arch the PVC in a quansit hut style. Use larger size PVC, like one inch. Tie pipe frame together with tie wire. Hammer in re-bar or metal pipe a the right angle to ancker the PVC and the pipe should slip right over it. Use dirt of sand bags to hold the bottom of the plastic. Several growers in our area do their seedling starts in temp green houses like that.

I use a similar setup to others in this thread, although some of my trees are too large to easily cover. I use 10x12 frost blankets, and prefer to use them double-thickness, but on the larger trees must use them single-thickness. The largest trees have a ringed base made out of 48" fencing wrapped with black tarps (held against the ground with bricks), and when it gets under 35F I attach the frost blankets over the top with clothes pins and clamps.

It's important to hold the cloth away from leaves and branches. Cold will wick through even special frost blankets.

For heat I use a 140-foot heating cable, with a few feet coiled underneath each tree. I think it's 5 watts per foot, so each tree gets about 40-45 watts or so. For the trees ringed with black tarps, I must go out in the morning when the sun comes up and at least open a corner of the frost blankets -- otherwise the trees will be toast. The reflective blankets can remain in place on the other trees during the day.

It's worked on my citrus and mangos for three seasons so far, with temps each winter into the low 20s. Earlier this year I put in some pygmy date palms by out front door, and am protecting them the same way using another heating cable.

-Bruce

softmentor:

Unfortunately I planted my citrus where I would be most proud of them, which was along the fence which is beside a driveway. There's a tree (china berry) that my wife hates over my little patio, which I've thought (if I ever bend to her wish) of removing and putting a covered patio there, but also make it into a convertible green house in the winter (how I would do this, I confess I don't know). If it was heated via outdoor fireplace in the winter (or small space heater) and swamp cooled in the summer (sometimes) I'd use it more, once I get out of school in 3 years or so *grin*.

I *did* think of burying a ducting network of large PVC, like 4" or something and using them to do a forced heat (heat and return for each tree) and then finding an old furnace to run on "low" with each tree covered of course, to minimize heat loss. Oh the silly engineering projects one can dream up when one creates their own problems.

An enclosed deck on our mobile home was another idea. I just need to heat it "enough" to keep the few weeks of 20s from killing them.

Right now they are (almost done) wrapped in pallet wrap with the lights inside. I'm using the old line-voltage thermostat from last year, as I haven't tinkered with the solid-state idea yet. The look pretty with the multi-colored C7 bulbs glowing, each tree with either 75 or 50 bulbs. Very Christmasy.

bcfromfl:

I've read about date palms, and was thinking that they were good down into the teens. Is that not so?

Kev.

My first baby citrus trees (one meyer lemon and one Bearss lime) went into the ground last week. I listened with horror to the weather report that the temps may drop to 34 degrees this week. Here is my question. There are landscape lights about 2 feet from each tree. If I tent the little trees and include the light inside the tent (I'm talking plastic sheeting secured by rocks), will the landscape light provide enough heat?

I could also buy some Christmas lights, but the closest outlet is about 100 feet away in the outside BBQ. Should I do that or will the landscape light work? Will the landscape light provide enough heat WITHOUT tenting? I appreciate your advice!

Thanks!

Suzi

I live in SW Louisiana and have planted orange, lime, and lemon trees for the last 3 years--I lose a few every year when the temps get below 30 degrees. I am planning on using freeze protection cloth this year--does anyone have any idea what temperature is the point of danger and what is the best mulch to use for freeze ptotection--Thanks.
Mike

It's my understanding that oranges and grapefruits are a LITTLE more hardy than lemons and limes, but not by a lot i.e. your orange might be OK with a brief dip to 30 but a lemon or lime is likely to be seriously hurt or killed.

So far my key lime has made it through 19 degrees with it's christmas lights and yard bag over it. Mr. Pineapple has been OK with it's flood lighting too, although some of it's outer leaf edges suffered that night that went to 19.

kevinh -- sorry, I was out of town for a few days.

The Roebelenii pygmy date palms can't handle frost...at least if you want to keep the fronds. They'll return in the spring with a few new ones from the top (if the cold isn't too severe), but I prefer to keep the previous seasons' growth as well. I have two clumps of about 8-10 of various sizes, and it requires two 10x12 frost cloths over the fencing around the perimeter.

-Bruce

I am fascinated by this thread and love the pics! anyway, have 3 citrus, a fig and a persimmon in 26" clay pots on the front patio. I have been very worried about them as I moved from a zone with no days below freezing and here it can get in the 20's. Last night's forecast was for 28.

Anyway, my trees: all betweem 4-5 years old, lemon with blooms, small lemons and fully ripening lemons, (or crops in 3 stages,) my satusuma with a full crop of ripening tangerines. Fig and persimmon appear to be dormant. All appear to be fine with no protection at all. I am stunned. Do you think the pots are making a difference?

From my understanding and short experience, most citrus are ok down to 26 (depending on rootstock...trifoliate is a bit more cold hardy than sour orange). There are of course lots of other factors, such as frost (frost does more damage than freezing temp), length of freeze, variety of citrus (limes are least cold-hardy), maturity of the tree, etc.

In pots, I would just water them right before a freeze and make sure they have overhead protection from frost, and I would not worry about a few hours in the upper 20's.

John Bonzo, not all citrus can take 26. You mentioned limes and they definitely can not. But yes, many can take a short frost that is below 32. But it varies by variety and 26 is not at all a reliable number. That's pretty cold for most varieties.
Also, I don't think root stock changes the grafted part's sensitivity, but only the root stock it's self is more or less hardy.

Softmentor - You are very right on the many number of factors that determine cold hardiness (others we did not mention: acclamation to cold and overall health of the tree)...there is certainly no "magic number."

I have found that upper 20's for a few hours are fine for oranges, grapefruit, and meyer lemons. Other lemons, citrons, limes, etc. wouldn't like that I am sure. From my understanding, Trifoliate orange rootstalk actually does add some protection because it is the only citrus that goes completely dormant in the winter.

According to John Panzarella (a local citrus guru for Southeast Texas), "PT goes dormant in the winter, so reduces the water flow to the scion and gives the scion a few degrees of cold protection. PT will not start growing and producing tender new growth with a few days of warm weather in the winter." The last sentence is especially important for Texas, as in the winter we have frequent gulf breezes battling arctic cold fronts.

So far, here are my unprotected lows for my varieties:

Rio Red Grapefruits (2 trees planted at the same time by previous owner)- 26 F (4 years old, south side of house, pine trees overhead) -- tree was covered in snow (maybe insulated it a bit??), I was very surprised that there was no damage.
Okistu Satsuma - 29 F (planted fall 2008, north side in the yard, no overhead protection at all)
Meyer Lemon - 28 F (planted spring 2007, north side of house, no overhead protection)
Moro Blood Orange - 28 F (planted spring 2007, in yard with no protection)
Lakeland Limequat - 29 F (planted fall 2008, north side of house, 2 feet from brick exterior of house)

As you can see, this is a very small sample size and only a brief history of data. Last winter was pretty warm, as has this winter so far. I wish I had a better way of measuring the length of the freeze and other variables.