Yes, certainly just the mountains save the South Coast of Crimea from such strong frosts. And also rather deep Black Sea along the South Coast. Now its temperature is +6C - +8C.
And one more remark: on the 1-2 of February it was till -11,9C in Nikita, and in Yalta it was till -10,1C
At the same time in Nizhnegorsk, Crimea (130 km from Yalta to the north-east) it was -35,2C.

Hi everyone, just picked up a fruit of my hana-yuzu (sold as sudachi which is totally wrong), the fruit was small and really like a mini-yuzu. It is surprising to have a rippen fruit so late in the season, probably due a late flowering. This caracteristic is really of my interest. Has anyone observed regulare late flowering on yuzu cultivars? The plant was grown in a greenhouse, so perfect conditions.

gerdhart Sudachi does look like a mini Yuzu. Sudachi is normally harvested green in late Aug or early Sept.

thanks Laaz, well yes, the sudachi looks like a mini-yuzu but a fully ripe fruit is orange and totally round with few seeds and a distinct flavor, different from the yuzu and difficult to peel of. the hana-yuzu (or hanayu) is truly a mini-yuzu in all aspects, including the taste of the peel (which is less strong to my palate)
I'll post pictures of both fruits
so my little hana-yuzu started to grow now a it shows some little flower buds. the fruit I picked up was definitely a late flowering from last year...
any chance to induce late flowering using specific fertilizers like more phosphorus during the summer?

Second summer flowering is ussual for citrus cultivars - it doesn't mean that this specimen is "late" (If some cultivar is called "late" it means that it takes longer time to ripe.)
Most of my citrus plants are flowering more than one time per year. I have a feeling, that on some plants, second flowering mainly occures, when first spring flowering is "not succesful" - means plant do not set fruit. - So may be if you remove flower buds from first - spring flowering, plant will try it again in summer. - who knows
BTW: I think that Hana (means - flower) yuzu is an ornamental form of yuzu with many nice flowers and Hanayu is citrus hanaju. But I am not sure.

So, here is link to page with pictures of citrus hanaju:
http://www.alpine-plants-jp.com/himitunohanazono/hanayu_himitu_1.htm
It is papeda from the same group as Yuzu, Yuko or Sudachi.

thank you Radoslav for this information. very interesting your suggestion, I should try on one plant to see if it works.
yes you're right, hana means flower in Japanese and indeed, the hanaju is cultivated more for its flowers than its fruits in Japan.
I found some very little information on seedless yuzu they should have names like Kinnosu, N°1-754, Xiecheng, Zhenchen, ..., has anyone heard about these cultivars?
the yuko has few to no seed but is different from the yuzu, for the taste of the peel and the flesh which has very low acidity (quite watery). the kabosu also is different, sour and the peel has a less stronger flavor than the yuzu

The group of six trees of Yuzu wich grow up in Nikita botanic garden have been nearly 100% defoliation:










and now it is clear that top of crown of one of the trees was destroyed by frost:



Now all the trees look quite well:



and on the south-west side I could see the young fruits.

Here are frozen fruits wich there were on the ground in February:

Forward,
The seeds that I got from you in March, were they coming from the smaller frozen fruit on your photo?

Yes, it's exactly that fruit!

In a spring I got five seeds from this fruit. I was not hoping for much, since it was frozen for weeks, I thought the the chances for germination are mince.
Nevertheless, I had four germinations. Two were rotten soon after. It was of no surprise, since all Yuzu I tested before are hardly compatible with local phytophtora strain.

By the beginning of July two survived seedlings are showing drastically different appearance as well as a vigor of growth:



Now:

It is very interesting, because my seedlings are 3-4 cm of height.