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Author Topic: How much cold can citrus trees tolerate  (Read 1218 times)

Millet

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How much cold can citrus trees tolerate
« on: December 12, 2016, 03:49:27 PM »
Cold weather is on its way, and many people are concerned about their citrus trees. One of the most common questions I get from gardeners is, "How much cold can citrus trees tolerate?" Because there are a number of variables, it's difficult to pin point a "threshold" temperature at which it becomes necessary to protect your trees.

There are three basic factors in determining freeze susceptibility of citrus trees.
The type and age of the citrus: Satsumas are the most cold hardy of the commonly grown citrus species in Louisiana. Kumquats follow with just a slightly less amount of cold hardiness. The order from most cold hardy to least cold hardy are: satsuma, kumquat, orange, grapefruit, lemon and lime. A citrus tree increases in hardiness as it gets older. Older trees with larger, denser canopies deal with the cold better as they trap more heat than smaller trees or unhealthy trees with thin canopies.
How cold it gets: Threshold temperatures are approximately 20 degrees for satsumas and kumquats and about 25 degrees for all other citrus trees. Trees will be damaged or killed by temperatures in the teens.

The duration of the sub-freezing temperature: If the temperature is below freezing for 24 hours or more, you should expect damage. All ripe fruit should be harvested from trees prior to a significant freeze. Temperatures cold enough to damage the tree also will ruin the fruit. It takes temperatures in the mid- to low 20s for five to 10 hours to freeze the fruit. The most cold hardy parts of the tree are the mature wood of major branches and the trunk.


If a citrus tree is gradually exposed to cooler temperatures, a process called hardening occurs, and trees become more tolerant to freezes. Chilly but above-freezing nights (in the 30s and 40s) that occur during the fall and early winter make the trees better able to handle freezes.

Severe freezes taking place when only mild weather has occurred previously are more likely to cause significant damage. This has been a relatively warm fall so our citrus trees are not well hardened at this point. Still, the temperatures this weekend should not produce severe damage.

The best way to lessen cold damage to citrus is to maintain healthy trees. Cultural practices that tend to induce and maintain dormancy in winter should be used. These methods include avoiding late summer or fall fertilization or pruning. Vigorous trees may recover from cold injury. Weak trees that are showing disease, insect damage or nutritional deficiencies are the ones most severely damaged and are the slowest to recover after freezes. fore covering, the tree could be generously wrapped with small, outdoor incandescent Christmas lights to provide additional warmth and increase the level of protection. Incandescent Christmas lights will not damage the tree even if they come into contact with it.

The frame and cover could stay in place indefinitely, but will need to be vented. Air temperatures within should not be allowed to go above 85 to 90 degrees. Venting should be provided on sunny warm days to prevent overheating and to maintain a supply of fresh air.

For trees too large to cover, banking the lower trunks of trees with soil or using tree wraps of bubble wrap, foam rubber or Styrofoam will help prevent cold damage to the trunk. This must be done before the first killing freeze and can be left on through the winter. Trunks should be treated with a copper fungicide before wrapping to prevent disease. Or the coverings could be applied during freezes and removed during mild weather.

Although tree tops may still be lost during freezes, a tree can recover if its trunk and root system are intact. Banking or wraps should be removed in the spring.

If the weather has been dry for a week or more in advance of a cold front, water your citrus trees. Trees that are drought stressed may experience more cold damage. This should be done a day or two before the freeze is expected.

Do not prune in the late summer or fall. Late pruning stimulates new growth that may not mature before winter, making it more prone to cold damage. In addition, pruning reduces the size of the canopy going into the winter, and this also reduces cold tolerance.

If pruning is needed, it should be done in early spring. Cuts should be made at branch crotches leaving no stubs. Prune to maintain a full, dense canopy. Trees need good leaf canopies to cut wind speed through the canopy and reduce the rate of cooling.

Leaves radiate heat to each other. Outer leaves may be lost to a freeze, but complete loss of inner leaves is averted by a thick canopy.

Fertilizer should be applied to citrus trees in late January or early February. A general-purpose fertilizer or citrus fertilizer may be used following label directions. Spread the fertilizer around the edge of the branches in the area of the feeder roots. Late summer or fall applications of fertilizer should be avoided as they can reduce the cold hardiness.

Avoid using oil sprays to control insects during the fall and winter. Horticultural oil sprays may decrease cold tolerance.

We potentially have a lot of cold weather yet to come this winter. Cover smaller trees as needed to protect them, and protect the trunks of larger trees if practical.

Keep things in perspective. We generally do not see significant damage if temperatures stay in the mid- to upper 20s and only stay below freezing for a few hours

http://www.nola.com/homegarden/index.ssf/2016/12/how_to_protect_citrus_trees_fr.html
« Last Edit: December 12, 2016, 03:50:59 PM by Millet »

Tom

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Re: How much cold can citrus trees tolerate
« Reply #1 on: December 12, 2016, 06:28:58 PM »
Great article and very timely !

mrtexas

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Re: How much cold can citrus trees tolerate
« Reply #2 on: December 12, 2016, 09:26:28 PM »
The reason we can grow citrus here near Houston is freezes seldom last longer than 3-4 hours.  They begin at around 4am and are done with first light. Since I moved to the SW Houston exurb area in 2013 there have been no freezes what so ever. Last citrus killing freeze was 1989. There have been a very few short duration 20F freezes since then. It has snowed 2 or 3 times and the snow only stuck once. I really hate cold and dark weather and thankfully we only get 2 or 3 weeks of below 70F weather a year. I was born in Seattle but can't comprehend how anyone could suffer 6 months of rainy weather in the 40s and very short days.

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #3 on: December 13, 2016, 03:44:51 AM »
 After growing citrus in ground in freeing zones for years, I have to say that Grapefruit is highly cold tolerant.  Never even got leaf burn from 15F where even the kumquats and calamondins suffered a little.  Oranges definitely do not have them beat, and my satsumas dropped leaves and suffer branch die back at 20F.
-Adam

adriano2

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Re: How much cold can citrus trees tolerate
« Reply #4 on: December 13, 2016, 04:36:20 AM »
Thank you Millet for this text. I was just wandering what could happen to my balcony trees, after i forgot to close balcony enclosure last saturday. When I came back home at 6 in the morning the temperature on the balcony was -1,9. Probably nothing serious happened, because that temperature lasted couple of hours. So far i see no damage, but it is still to early to say.

Millet

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Re: How much cold can citrus trees tolerate
« Reply #5 on: December 13, 2016, 12:01:07 PM »
Adrino2 -1.9 C equals 29-F.  I doubt that a brief low temperature of -1.9-C would cause any damage except possibly to a new young seedling. .

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #6 on: December 13, 2016, 12:21:58 PM »
Thank you Millet for this text. I was just wandering what could happen to my balcony trees, after i forgot to close balcony enclosure last saturday. When I came back home at 6 in the morning the temperature on the balcony was -1,9. Probably nothing serious happened, because that temperature lasted couple of hours. So far i see no damage, but it is still to early to say.

Pretty sure even limes will be OK for just a few hours at that temp.
-Adam

LaCasaVerde

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Re: How much cold can citrus trees tolerate
« Reply #7 on: December 13, 2016, 12:48:36 PM »
After growing citrus in ground in freeing zones for years, I have to say that Grapefruit is highly cold tolerant.  Never even got leaf burn from 15F where even the kumquats and calamondins suffered a little.  Oranges definitely do not have them beat, and my satsumas dropped leaves and suffer branch die back at 20F.

Here in 8b/9a oranges left to their own will all perish unless protected until larger- then every fourth or fifth year they too may sucumb to  a 18-22 degree hard freeze. Grapefruit on the other hand grow wild here... I believe grapefruit trees themselves survive due to the much larger mass of the trunk/tree. Neighbors tree is 30 feet tall and look like a...tree. Much larger than other citrus in general.

Also ...leaf temp is more important than outside ambient air temp. Too many worry about air temp. Im more worried about the conditions that are occuring with the cold.  When there is no wind and I can see the stars on a clear cold night- danger,danger.  This is more dangerous because air temp may be say..29 outside for 4 hours but the leaf/trunk through super cooling(radiative cooling) can be 2-3 degrees cooler and sub 29 for 6 hours. 

On the other hand- when it is windy and the air is moving I rely more on the actual weathermans forcast low temp as the wind keeps the citrus the same temp as the air.


Millet

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Re: How much cold can citrus trees tolerate
« Reply #8 on: December 13, 2016, 03:02:58 PM »
I go along with La Casa Verde on the cold hardiness of grapefruit.  It is the older very large think branched grapefruit trees that survive some freezes.  Otherwise - dead.

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #9 on: December 13, 2016, 04:53:29 PM »
I go along with La Casa Verde on the cold hardiness of grapefruit.  It is the older very large think branched grapefruit trees that survive some freezes.  Otherwise - dead.

Sorry to disagree, but, I disagree from experience.

Some years back we had an abnormal cold hit which dropped beneath 15F.  I lost 6 orange trees plus an owari.  Everything suffered leaf burn, branch die back, etc etc.

Except the grapefruits.  I had everything from an 18 inch sapling to a tree and between various sizes and varieties.  No damage on any grapefruit except the pomelo cousins.  The 18" was only in ground for about 6 months at the time, and only its newest "light green" starting leaf tips showed stress by slightly curling.

Whoever came up with grapefruits being sensitive to cold has obviously never grounded one in a freeze worthy climate.

As for below 10F, I cannot say.  But I have personally witnessed them handle the teens and twenties without dropping so much as a leaf.

Grapefruits are tough, fast growing and resistant.  Love them.
« Last Edit: December 13, 2016, 04:55:40 PM by Viking Guy »
-Adam

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #10 on: December 13, 2016, 04:54:15 PM »
.
-Adam

LaCasaVerde

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Re: How much cold can citrus trees tolerate
« Reply #11 on: December 13, 2016, 06:00:20 PM »
I believe we are - you, I and Millet-saying the same thing. I see them growing wild here as in ...they have survived from saplings and are now full size trees that have survived unattended for 30 years... so in essence yes I believe graprefruit are more cold hardy than many expect.  An attribute as they mature is also their size...which I believe in the long run is a survivability asset here. 

 

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #12 on: December 13, 2016, 06:53:11 PM »
I was disagreeing with the idea that only large grapefruit survive cold and young ones don't.

Young ones are just as cold hardy.
-Adam

Citradia

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Re: How much cold can citrus trees tolerate
« Reply #13 on: December 13, 2016, 09:32:48 PM »
I have a sapling seedling ruby red grapefruit that I planted in ground in line with citranges and Ichangs that are protected by high tunnel and water barrels in winter. The seedling GF was about two feet tall and multitrunked, and with low of 10 degrees last winter, it did defoliate, but survived and grew bigger this year. My Rio Red GF partially defoliated two winters ago when I forgot to plug in small space heater in its PVC tent enclosure when low of 19 degrees one night, and it didn't bloom the next spring. It's seven feet tall now, bloomed this spring, but didn't hold fruit. I know my Kimbrough satsuma survived 19 degrees or lower an entire night and into next day without space heater and bloomed the next year without leaf drop.

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #14 on: December 13, 2016, 09:47:41 PM »
Sometimes our efforts to protect them can cause more harm than good, especially depending on weather conditions (air movement, humidity, etc).  Glad to hear they bounced back after 10 degrees.  That's brutal.
-Adam

adriano2

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Re: How much cold can citrus trees tolerate
« Reply #15 on: December 14, 2016, 03:06:51 AM »
https://www.facebook.com/184667068215844/photos/a.184668528215698.51561.184667068215844/184669261548958/?type=3&theater

https://www.facebook.com/184667068215844/photos/a.184668528215698.51561.184667068215844/184669331548951/?type=3&theater

those are grapefruit photos in some nursery in Bosnia and Hercegovina, close to border with Croatia, but still some 30 km far from the coast with regular -10 C at least once a year. I was very surprised to see grapefruit growing there, because it is not citrus friendly enviroment. It seems only grapefruit and satsumas can grow outside in this place. 

adriano2

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Re: How much cold can citrus trees tolerate
« Reply #16 on: December 14, 2016, 03:08:35 AM »
photos 16 and 17 in the album

cory

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Re: How much cold can citrus trees tolerate
« Reply #17 on: December 14, 2016, 02:49:34 PM »
Wow!  Large trees loaded with fruit.  It makes me feel like I should try a test tree in a protected spot in my yard.

Cory

Viking Guy

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Re: How much cold can citrus trees tolerate
« Reply #18 on: December 14, 2016, 02:55:15 PM »
Wow!  Large trees loaded with fruit.  It makes me feel like I should try a test tree in a protected spot in my yard.

Cory

There is one growing in a cemetery in Knoxville, TN.

Pretty sure it would be fine, but NJ would be pushing the bar, heh.
-Adam

Laaz

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Re: How much cold can citrus trees tolerate
« Reply #19 on: December 14, 2016, 03:20:29 PM »
Bob, you probably remember the ruby red I grew from seed from the store. It is now over 25 ft tall and loads up every year.


Laaz

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Re: How much cold can citrus trees tolerate
« Reply #20 on: December 14, 2016, 03:21:00 PM »
And it has never been protected...

Millet

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Re: How much cold can citrus trees tolerate
« Reply #21 on: December 14, 2016, 05:47:36 PM »
Thats because you have the magic hand.  What do you do with all that fruit.  Seems to much to consume.  Laaz that is a great picture to demonstrate how the tree got its name.  See how the fruit hangs in clusters like grapes on a vine.  When grapefruit was first discovered it reminded the finder of grapes, and so he called the tree grapefruit..
« Last Edit: December 14, 2016, 05:50:46 PM by Millet »

Laaz

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Re: How much cold can citrus trees tolerate
« Reply #22 on: December 14, 2016, 06:25:39 PM »
Give most of it away...

Citradia

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Re: How much cold can citrus trees tolerate
« Reply #23 on: December 14, 2016, 08:49:21 PM »

"There is one growing in a cemetery in Knoxville, TN."
Viking guy, do you mean a grapefruit is growing in a cemetery in Knoxville,TN, or a citrumelo? Knoxville is similar climate to where I am in mountains of NC, and I'm lucky to grow citrumelos without protection here.

LaCasaVerde

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Re: How much cold can citrus trees tolerate
« Reply #24 on: December 14, 2016, 08:51:43 PM »
Laaz, what kind of temps do you get there during winter? Here usually 10-15 days total usually above 27 at night. Some years though down to 20 but for a night or two at the most. Barley 9A here

You must be really near the coast... seems your area is pushing the zone for outdoor citrus.
« Last Edit: December 14, 2016, 08:55:57 PM by LaCasaVerde »

 

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