Roberto,
It will be a real test for my in ground citruses in the spring.
Defreezing of the ground has started only today, after two weeks of cold and snow. And it is our second froze this winter.
I put some fleece cover in the coldest night but only on my citremon. The rest were open to elements.
I shall put some photos soon.

A short visit in my garden showed more or less total loss of foliage of all in ground citrus after -14°C and a week of permanent freeze. I have Citsuma, HamlinXFlying dragon, some Citrumelos, Trifeola, PoncirusXsunki mandarin and a whole sample of C. ichangensis. Now the question is: what will survive?

Hello IlyaC and Roberto. This was a very interesting thread to read, very enjoyable. How are your plants doing now? IlyaC did your ichangquat survive? Roberto are your hardy citrus ok? Any pictures would be welcome.

IlyaC could you provide a link to where I can buy the ichangquat please? I tried to google Bernhard Voss but the site I found had pages missing and I couldn't find anywhere to buy the ichangquat.

Roberto could you provide links to where you bought your various hardy citrus please?

Thanks!

Ishangquat has not flowered in the spring, But starting from July has several several periods of flowering. Last one occurred in October(picture)
There were dozens of immature fruits but they were damaged by -9C in the December. The winter here this year has been cold, but without records. For the moment all my hybrids look good.



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Here is a link to B.Voss site:

http://www.agrumi-voss.de/citrus.htm

Ishangquat is listed as N8 on the Frosthartere Citrus page

Thank you for the update, link, and pic. I'm glad your hybrids are doing good, a pity about the fruits not surviving the winter.

It says on the B.Voss site the ichangquat takes -12C but you and others have observed it takes -16C? This is very encouraging. Am I right in thinking the ichangquat is the most cold hardy citrus plant other than the poncirus trifoliata?

There is also the ichangensis x trifoliata but I cannot find much information on this. The B.Voss site says it takes -12/-15C which is surprising because I would imagine it would be hardier than the ichangquat, given that it has poncirus rather than kumquat as a parent.

A peculiarity of C. ichangensis, and all of its hybrids, is that they all flower and fruit more freely if grafted onto the trifoliate orange rather than grown on their own roots. (Hardy Citrus For The Southeast) - Millet (695-)

Lemandarangequatelo,

Over the years I planted and killed many "hardy" citrus hybrids. It seems that fatal for them are different sudden weather fluctuations.
The cold tolerance reported in one climate and for short period of observation are very misleading.
For the moment, I have consistent not at all damage only for Ishangquat and Swingle 5star citrumelo. And of course poncirus.

IlyaC, thank you very much for the valuable information. The ichangquat and swingle 5 star citrumelo are now top of my list of next citrus plants to get. What's even better is that both of these have fruit that is reasonably tasty. Have you ever tried to cross breed ichangquat with swingle 5 star citrumelo? This sounds like a very interesting cross to do!

Not yet, but it is in my plans for this spring.

This is awesome, if you have time to do it please keep us informed.

Lemandarangequatelo,

alas I am not as lucky as Ilya who lives near Paris. In Vienna we've had a serial of quite cold and damaging (at least to citrus) winters. Although most of my hybrids survived they froze down to the ground. The ongoing winter was a little bit milder but the problem is that most of the young upgrow of last summer will die back. My Citrumelos, Trifeolas and Citsumas will never reach more than 10inches...
There is one quite promising hybrid: PoncirusXSunki-mandarin and another one: Citsuma "Prague". Prague-scion survived last winter totally unprotected on a 1m high rootstock. And the nice thing about this Citsuma is, that the fruits are sweet and have no Poncirus-aftertaste (referring to Bernhard Voss). My plan for the future is to protect my citrus trees (merely against sun in winter) but not heat them.
Greetings from Vienna
Robert

Robert,

thank you very much for sharing your excellent information. I'm sorry to hear about the dieback on most of your citrus trees. I'm happy to learn about the two promising hybrids PoncirusXSunki-mandarin and Citsuma "Prague". I hope these hardier hybrids, and your new plan to protect your other citrus against the sun during winter, prove very successful for you.

I have now added PoncirusXSunki-mandarin and Citsuma "Prague" to my list of citrus trees to get along with the ichangquat and swingle 5 star citrumelo. In the future I will use them to try and make some new good tasting hardy hybrids.

Dear Ilya, it will be interesting to know and probably to see how your Ichangquat is growing and fruiting now.Thanks.