We are entering the shivering season for the Central Valley, Bay Area and low foothills. Late November through mid-February is the most critical time here for protecting frost-susceptible plants.
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Frost Cloths Protecting Lemons, Mandarins, Oranges |
This is especially true for citrus tree owners, who are anxiously keeping an eye out on the upcoming weather forecasts.
Several days before an expected frost (temperatures dipping down to 32 degrees) is the time to gather the necessary implements to protect your citrus trees, including giving the ground beneath them a good soaking (moist soil is better than dry soil at moderating the temperature beneath the tree).
Most gardeners first thoughts about protecting their citrus trees during a frost or freeze is, "protect the fruit!"
Four Winds Growers, the Winters-based wholesale grower of many excellent varieties of citrus, offers the Citrus Variety Information Chart at their website, FourWindsGrowers.com.
Included in that chart is extensive information about each citrus variety, including suitability for indoor growing; its bloom and fruiting seasons; its recommended summer heat level to produce good fruit; and, its minimum tolerable temperature for preservation of fruit quality.
The chart points out that lemons, limes and citrons are most sensitive to frost, while sweet oranges, grapefruit, tangerines and calamondins are intermediate. Kumquats and Owari Satsuma Mandarins are the most frost-tolerant, braving temperatures into the twenties (that would classify as a freeze).
From that chart, here are the temperatures (in degrees Fahrenheit) at which citrus fruit damage may occur.
Sweet Oranges
Washington Navel Orange 28
Trovita Orange 28
Cara Cara (Pink) Navel Orange 28
Lane Late Navel Orange 28
Robertson Navel Orange 28
Shamouti Orange (Jaffa Palestine) 28
Valencia Orange 28
Midknight Valencia Orange 28
Trovita Orange 28
Cara Cara (Pink) Navel Orange 28
Lane Late Navel Orange 28
Robertson Navel Orange 28
Shamouti Orange (Jaffa Palestine) 28
Valencia Orange 28
Midknight Valencia Orange 28
Blood Oranges
Moro Blood Orange 28
Sanquinelli Blood Orange 28
Tarocco Blood Orange 28
Sour Oranges
Bouquet De Fleurs Sour Orange 28
Chinotto Sour Orange (Myrtle-Leaf) 28
Seville Sour Orange 28
Bergamot Sour Orange 32
Bouquet De Fleurs Sour Orange 28
Chinotto Sour Orange (Myrtle-Leaf) 28
Seville Sour Orange 28
Bergamot Sour Orange 32
Mandarins
Gold Nugget Mandarin (Patented) 26
Tango Mandarin (Patented) 32
Owari Satsuma Mandarin 24
Dancy Tangerine 32
Clementine Mandarin (Algerian) 28
Murcott Mandarin 32
California Honey Mandarin 32
W. Murcott Mandarin 32
Kinnow Mandarin 32
Kara Mandarin 32
Page Mandarin 32
Piie Mandarin 32
Kishu Mandarin 32
Gold Nugget Mandarin (Patented) 26
Tango Mandarin (Patented) 32
Owari Satsuma Mandarin 24
Dancy Tangerine 32
Clementine Mandarin (Algerian) 28
Murcott Mandarin 32
California Honey Mandarin 32
W. Murcott Mandarin 32
Kinnow Mandarin 32
Kara Mandarin 32
Page Mandarin 32
Piie Mandarin 32
Kishu Mandarin 32
Lemons
Improved Meyer Lemon 32
Eureka Lemon 32
Lisbon Lemon 32
Ponderosa Lemon 32
Variegated Pink Lemon 32
Yen Ben Lemon 32
Mediterranean Lemons
Villafranca Lemon 32
Genoa Lemon (Gea) 32
Limonero Fino Lemon 32
Improved Meyer Lemon 32
Eureka Lemon 32
Lisbon Lemon 32
Ponderosa Lemon 32
Variegated Pink Lemon 32
Yen Ben Lemon 32
Mediterranean Lemons
Villafranca Lemon 32
Genoa Lemon (Gea) 32
Limonero Fino Lemon 32
Limettas
Millsweet Acidless Limetta 32
Marrakech Limetta 32
Millsweet Acidless Limetta 32
Marrakech Limetta 32
Limes
Bearss Seedless Lime (TahitiPersian) 30
Kaffir Lime (KiefferThaiWild) 32
Meican Lime (Key) 32
Thornless Meican Lime 32
Meican Sweet Lime 30
Palestine Sweet Lime 30
Rangpur Lime 32
Bearss Seedless Lime (TahitiPersian) 30
Kaffir Lime (KiefferThaiWild) 32
Meican Lime (Key) 32
Thornless Meican Lime 32
Meican Sweet Lime 30
Palestine Sweet Lime 30
Rangpur Lime 32
Grapefruits
Oroblanco Grapefruit 32
Rio Red Grapefruit 28
Star Ruby Grapefruit 28
Chandler Pummelo 28
Cocktail Grapefruit 28
Chinese Grapefruit 28
Melogold Grapefruit 28
Oroblanco Grapefruit 32
Rio Red Grapefruit 28
Star Ruby Grapefruit 28
Chandler Pummelo 28
Cocktail Grapefruit 28
Chinese Grapefruit 28
Melogold Grapefruit 28
Kumquats
Meiwa Kumquat 28
Nagami Kumquat 24
Indio Mandarinquat 26
Centennial Variegated Kumquat 30
Nordmann Seedless Nagami Kumquat 28
Marumi Kumquat 26
Eustis Limequat 32
Meiwa Kumquat 28
Nagami Kumquat 24
Indio Mandarinquat 26
Centennial Variegated Kumquat 30
Nordmann Seedless Nagami Kumquat 28
Marumi Kumquat 26
Eustis Limequat 32
Citrons
Buddha's Hand Fingered Citron 32
Etrog Citron (Ethrog) 32
Buddha's Hand Fingered Citron 32
Etrog Citron (Ethrog) 32
Other Interesting Varieties
Minneola Tangelo 28
Australian Finger Lime 32
Yuzu 24
Calamondin 32
Variegated Calamondin 32
But what about the overall health of the citrus tree? How low can temperatures go during a freeze event before the tree is toast?
Minneola Tangelo 28
Australian Finger Lime 32
Yuzu 24
Calamondin 32
Variegated Calamondin 32
But what about the overall health of the citrus tree? How low can temperatures go during a freeze event before the tree is toast?
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And that's for a citrus tree in tip-top shape: good health, with moist soil around it during a freeze. Cedar uses the example of a Meyer lemon tree:
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Blanket + Tomato Cage for Citrus Protection |
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Chandler Pummelo, Pummeled by 2010 Freeze |
You may recall Thanksgiving Week of 2010, when morning low temperatures dipped well below freezing for six days in a row, led by a citrus-killing 27 degree morning on Thanksgiving.
When a large, cold-air mass moves in from the north after a storm in the winter, that is called an advective freeze. The one that sticks out in most gardeners' memories here was the freeze of mid-December 1990, when nighttime temperatures fell into the teens for several days in a row, with a couple of days that didn't climb above 32 degrees. To add even more injury, a second cold snap hit near the end of the month, with temperatures dipping into the mid-20's. Many of the most susceptible (frost intolerant) landscapes were completely lost; some nurseries never recovered.
"Our first year in the citrus business here in Winters was 1990-91. My wife, Mary Helen, and I have a Masters in Disaster," says Cedar Seeger.
Which is why Cedar is an adherent of watching the dew point, the temperature at which saturation has been reached, when water vapor condenses into water. The lower the dew point, the more danger of cold damage to your plants. One good online source for dew point temperatures is the National Weather Service's Tabular Forecast Page , which offers a forecast for two days in advance (that link is for Sacramento).
"A good watering going into an advection night is mandatory. If the ground and surrounding grass is wet, it creates a micro dew point environment around the trees. In a dry, cold La Nina winter such as we're about to get, it is important to remember the dew point concept. At 22 and below, it's full on emergency response, pile straw, hay around trunks, anything, lights, covering," says Cedar, a man who learned these lessons the hard way. But he is not an adherent of running sprinklers during a freeze.
"My experience with overhead sprinklers is that they more often than not freeze up, and then it's all over. And you are risking branch breakage on that ice-entombed citrus. Yeah, it can work, but screw it; it's messy, risky and a lot of work. Use the large Christmas lights and mid-weight frost covers. But pay attention to the trunk / rootstock. If that freezes, it's a goner."
Citrus trees most at risk to fatal damage from a frost or freeze are the young trees. It is vital that they be covered completely when a heavy frost or freeze is predicted, and provide protection for the trunk, bud union and rootstock area. That can include trunk wraps, newspapers, old carpeting. If possible, move small containerized citrus closer to the house, preferably next to a south or west-facing wall to maximize reflected heat.
I use beach umbrellas draped with plastic to protect my dwarf citrus. They come in two parts. The base stake stays planted in the soil during frost/freeze danger. The umbrella portion is collapsed during the day and removed to allow sun. That portion is returned to the base in late afternoon. Sometimes the temperature during the day is so low that the drape stays put. I use clothespins to keep the plastic attached to the umbrella similar to a shower curtain.
ReplyDeleteI am hopeful that we are in for a mild and wet winter in the valley. But I did purchase three new C-9 light sets from Emigh's just recently. Last year's freeze really walloped the lime and lemon trees to the point where they either produced nothing or very little in terms of citrus production this year. I'm not going to go through that risk again.
ReplyDeletewhen I lived in the area I would put large buckets of water all the way around plants that might freeze. I was giving them an extra layer of protection as all the water would have to freeze before the plants would also freeze. I used empty kitty litter pails and old clorox or coffee containers.
ReplyDeleteI have a Bearss lime tree that was about 4 years old in a large pot and it was producing really well. It froze all the way down to the roots but came back. It has been two years now and it is now about 3 feet tall but not blooming. Do you think the tree will ever produce again?
ReplyDeleteIf the growth has larger, leathery leaves than you remember...and there are nasty thorns along the stems...it is probably rootstock growth which will probably not bear (pun intended) edible fruit.
DeleteYep, the leaves are as you say and the thorns are there.. Oh well I guess I will have to go out and buy another. Thanks
DeleteHeya~
ReplyDeleteI don't know if you are still able to chit chat, but I recently got a Mandarin Orange. It is in a pot and a pretty small tree and I haven't transplanted it to a bigger pot because I was advised to wait for it to stop fruiting first.
Recently we had a bit of a cold snap and I had forgotten to bring it in. The tree and branches are fine, still green. But the leaves are dried and curled up. Anything I can do for it? For now I've been bringing it in at night and leaving it outside to get sunlight when it is warm (usually in the 60s/upper 50s daytime, but colder during the night).
Any advice? This is my first tree.
I have an orange tree here in Houston that had the leaves described and lots of thorns but no fruit. After 21 years it finally had 3 oranges, the next year a couple of dozen, and this year over 300! I thought it would never fruit, but never removed it. You never know.
ReplyDeleteLemons in Eugene, Oregon? With a bit of effort, one can grow lots of lemons up here but trees need to be covered now and then with a heater as needed. We are 8b here. My 7 foot tree is loaded. I give lemons away.
ReplyDeleteThank you! It's dipping into the mid 30s in Mississippi tonight and I brought all (blooming) limes and blood oranges into the garage. Everyone else is draped in Frost blankets during this cold snap.
ReplyDeleteI appreciate your page-very helpful!
These temperature limits are not accurate. It looks like the same info from Four Winds Growers. For example most mandarins will be much hardier than grapefruits and oranges. Mandarins should be hardy to 20 to 26F. Grapefruits are not as hardy as oranges. Don't rely on these temperatures.
ReplyDeleteI live in south Texas and we just suffered a deep freeze that lasted a few days. My mexican lime tree is about 12 years old...too large for me to cover. It has always been very healthy and have me a generous supply of wonderful lines. Right now the leaves have all turned a yellow color. I'm so sad and hoping I have not lost this wonderful tree.
ReplyDeleteI live I South Mississippi . I have a prized Satsuma, seedless variety that’s about 7 to 8 feet tall and wide. This Magnificient Specimen produces hundreds of delicious smaller fruits each year!!! We cover it in frost/ freeze times diligently! But there has come a mold/ blight patch to the trunks and limbs… Do y’all know a quick / clean / organic spray for this , please?!? The tree is 20 years old this year , and My Favorite Thing On Earth!!! Any Help Would be Appreciated! Thanks , Chris from Mississippi ! BTW; Thank You All For your Helpful Insights and kindnesses! 🙏🏻🤙🌸
ReplyDelete