Author Topic: Frosthardiness experience with citrusvarieties in zone 7, down to 3,2 F  (Read 519 times)

tedburn

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In summer 2020 I planted a lot of assumed frosthardy citrus varieties in my garden in ground. Due to the plants have been not so big I hoped to get a mild winter, but counted with the worst. And the winter got worse, we got 4 days and nights enduring frost down to 3,2 F ( - 16 C) and during the days frost with 100% full sunlight.
Heavy test for my citrus. Then from 20.2. it got warmer, but always change a few days warm, followed by colder days with night frost. So I show you the result after the severe winter. Hope it can help you to get more information of cold hardiness of citrus varieties 😋.
Regards Frank

kumin

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Excellent photos, some surprises. You had a colder Winter than I did.

tedburn

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thanks kumin, yes it was an ugly winter in our region

lebmung

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Nice comparisons. To increase the survival rate the graft union must be completely healed 2-3 years and the tree with a trunk diameter of 1 cm, then planted outside in soil.

tedburn

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Thanks Lebmung, for adding your experience, yes I think this are very true points. In my case, I know that my plants all have been risky ( young and small) but regarding the last warmer winters and using winter protection I decided the risk to be not so high. So hope for a good recovery this summer 😅.

vnomonee

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Like you I risked my small hybrids outside. My lowest in zone 7a this winter was 12f/-11c. My Yuzu defoliated at the very end of winter but it's pushing out new leaves now. My citrumelo had some leaves curl and dry up and then drop but kept at least half of them and is otherwise fine. My tai-tri didn't lose but 1 or two leaves.

tedburn

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Hello vnomonee, that sounds good for a new restart, congratulation. But it is very difficult to tell early after the freeze how severe the damage is.
My Ichangquat 245 looked pretty good in March and now there are still some more twig damages, perhaps also our bad spring this year with always changing warm weather with night freezes stresses the already harmed plants additionally.
So I'm really curious when the citrus start to grow again and finally to see what is then still damaged. At some small buds are already to be seen.
Think to give an update in a few weeks.

Citradia

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I’ve lost almost all poncirus hybrids when temps reached 5 degrees F and below over several years. Also lost 10 ft tall dunstan and swingle citrumelos when temps never got above freezing, hovering at or just below 32 degrees F for a week. I lost hybrids when they just started putting out new growth in March, when we got a low of 14 degrees, and these were protected in a high tunnel with water barrels next to each tree. The only hybrids that have survived at my place outdoors without being covered and heated by space heaters for the past decade are Dunstan citrumelo, citradia, and Thomasville citrangequat, and they have died to ground and came back from roots several times. I’ve lost several Dunstan and citradia trees too, but these are the only three specimens that I have left. I’ve lost the following over the years: Dunstan, swingle, citradia, rusk, Changsha, mortan, Nansho dai dai, ichangensis, Ichang lemon, carizo, yuzu. I’ve even lost some potted flying dragon one-year seedlings when zero degrees F all night two nights in a row. The small cracks at base of the tree trunk in spring means the tree is going to die; I had a citradia leaf out in spring despite a crack in base of trunk bark and it died suddenly soon after.

SoCal2warm

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I’ve lost almost all poncirus hybrids when temps reached 5 degrees F and below over several years. Also lost 10 ft tall dunstan and swingle citrumelos when temps never got above freezing, hovering at or just below 32 degrees F for a week. I lost hybrids when they just started putting out new growth in March, when we got a low of 14 degrees, and these were protected in a high tunnel with water barrels next to each tree.
From what I have observed, the amount of cold tolerance can go down if the citrus is covered in such a way that creates a greenhouse effect. The very warm daytime temperatures inside the covering then brings the citrus out of dormancy and can make even cold hardy citrus vulnerable to modest cold temperatures.
So I think it is important to describe the conditions of the covering, if that may have been creating a greenhouse effect.

tedburn

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I’ve lost almost all poncirus hybrids when temps reached 5 degrees F and below over several years. Also lost 10 ft tall dunstan and swingle citrumelos when temps never got above freezing, hovering at or just below 32 degrees F for a week. I lost hybrids when they just started putting out new growth in March, when we got a low of 14 degrees, and these were protected in a high tunnel with water barrels next to each tree. The only hybrids that have survived at my place outdoors without being covered and heated by space heaters for the past decade are Dunstan citrumelo, citradia, and Thomasville citrangequat, and they have died to ground and came back from roots several times. I’ve lost several Dunstan and citradia trees too, but these are the only three specimens that I have left. I’ve lost the following over the years: Dunstan, swingle, citradia, rusk, Changsha, mortan, Nansho dai dai, ichangensis, Ichang lemon, carizo, yuzu. I’ve even lost some potted flying dragon one-year seedlings when zero degrees F all night two nights in a row. The small cracks at base of the tree trunk in spring means the tree is going to die; I had a citradia leaf out in spring despite a crack in base of trunk bark and it died suddenly soon after.

Thanks for your much experiences, very interesting. What I also could observe:
That Thomasville is very cold tolerant, up to now no damage, not even a leave.
That the damages still get more severe the months after the longer deep freeze. Thats really difficult, because I think final result will only be seen in June or July. So I already have lost a Dunstan and my 5* Citrumelo is in pretty bad shape.

Citradia

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Re: Frosthardiness experience with citrusvarieties in zone 7, down to 3,2 F
« Reply #10 on: April 22, 2021, 02:14:03 PM »
Socal2warm, my hybrid citrus die when not covered at all from either too many cumulative days below freezing or from extreme low temps. The ones that broke dormancy in the opened ventilated high tunnel broke dormancy in mid March which is when everything is starting to bloom here. My point was that I get late freezes here and if citrus of any kind other than trifoliata is starting to push new growth, it needs to be kept above freezing at that time or it may die. Today is April 22 and I had a low this morning of 28 degrees and below freezing for five hours. Have had temps in 60’s and 70’s since Early March with one other 29 degree low a few weeks ago. Even my unprotected poncirus has already bloomed. I have to keep my greenhouse frames up and heaters ready to go up until Mother’s Day here. My satsumas and grapefruit are in full bloom and my seedlings and grafted potted citrus are all safe inside my heated enclosures last night and tonight because I am not taking a chance on loosing my crop from last year, still fruit on trees ( grapefruit and Meiwa), or this years blooms, or loosing my trees. My protected citrus grafted on trifoliata and FD actually brake dormancy later than my unprotected trifoliata trees. I think I am doing it right for my roller coaster climate since I have harvested fruit for the past 6 or more years.

tedburn

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here is the final update of the survivors (new green buds and no dry back anymore) and the candidates with still mortal risk (dry back goes on or rootstock got cracks) and the Dunstan which is already died.
Due to our very cold April ( coldest since many years) the plants start very slow growing.
The Thomasville had new shot and this was eaten by an unknown insect, so because the plant is still small I put it in a net for protection for a few weeks.

« Last Edit: May 02, 2021, 03:31:24 PM by tedburn »