N1Tri, and very cold hardy citrus.

[hear]

Citrus that can withstand 7b/8a, winters though lately have been rarely dipping 20s to my knowledge.

[zap]

How about some Isuzu's.
Sorry Yuzu's? I checked on Ebay, and the seller I have used is out of seedlings for the year.
Seedlings are considered best for extreme cold, because trees could freeze to the roots and Possibly grow back... possibly.
But grafted Yuzus, are Juicy, and slightly sweeter.
I have about twenty seedlings which I will baby through one season.

Thomasville citrangequat.  And Improved Vars are the way to go. 

"Trees .." some thing on ebay has yuzu seedlings still. And McKenzie Farms has several cold resistant Hybrids until they sell out each year.

There are photos online of a Yuzu tree outdoors, in downtown Portland, OR, USA. It looks at least two decades old to me?

Ichang lemon is more like a Grapefruit to me.
you also might try to search for improved cultivars of US852. (the F-1's are bitter) The hybrid cross was later repeated to create Nucellular, and Zygotic offspring, (for different purposes).

There is also, a VAR called Snow Lemon.
It's like Citrus Kulu, and that is also the name of a famous Valley in Indja where frost resistant lemons are grown.  US germplasm, labeled it an unstable hybrid, and discontinued it?   WTF??
Oscar Tintori Citrus is the only one I know of who carries the Snow Lemon.   (I have heard it is a somewhat reluctant bearer)

The Europeans are whupping the US's collective behind in development of cold resistant citrus.  So if you are outside the US, you will have far greater access to new varieties, for colder climates.   You can't import to USA legally at this time due to quarantine regs.

[Sylvain]

Snow lemon is Kulu lemon, not Kuzu. Also called citrus kulu but this is not an official name.
It is not really cold hardy,

[hear]

citrusvariety.ucr.edu/citrus/kulu_3487.html this Kulu lemon? Where is it available at?

[zap]

Hi Sylvain:
RE: Kulu Lemon, how cold can they go? Are the photos, with snow in the picture deceptive?
I can't find any gardening data for Kulu lemons.
I have read that Kulu is just a Poncirus hybrid. But I have seen photos of huge round grapefruit shaped "lemons" labeled citrus kulu.

Citrangequats, or Ichangquats might make it for hear's climate zone. With fruit it's a good idea to hedge your bets, AND plant more than one variety.   In case you turn out to hate one of the flavors.  Or the tree just never reaches it's potential in the one spot it got planted in. Every time you plant it's a gamble.

[Sylvain]

Hear, it seems this one is the right one:

citrusvariety.ucr.edu/citrus/kulu_3045.html

[zap]

hear; honestly my lemon tree froze back to the main trunk several times.   And that was in Northern California Zone 8.5 (Saclamento).

So not a good choice. BUT there was a 40ft plus lemon tree, with very large lemons, a couple of blocks away along a bike path.
I just threw that name out there to see if anyone had data about it. I have read that USC description before. There is another "accession card" for the two vars. But they are from seed - so F-2 hybrids. They did not breed true from seed, and had trifoliate offspring? (Poncirus species)

There were also "Japanese Grapefruit" trees left over from the Asian miners that had survived from the gold rush era, until the early 1970's. Approx 100 yrs. I-80 & SR-49 in Auburn,CA,USA.
I believe they are Ichang lemons. They look like grapefruit, have a yellow-white peel, and Juice like vinegar. Made excellent lemonade. Grapefruit tang...
(That grove is on my list!)

There is a cold citrus archive, and I will try to remember to post it here, It's not coming up on google right now, sorry.
Actually this forum, has an archive of older data, and there is a lot of information about cold hardy citrus.
They are almost all bitter, and used for cooking, mostly.

Temp ranges: en.wikipedia.org/wiki/Cold-hardy_citrus

Best wishes,
ZAP

[terry]

Is there some confusion on the Kulu
citruspages.free.fr/lemons.html#kulu

[zap]

There IS confusion.
There are old hybrids.
Nikita is available in Europe.
Not all trifoliate hybrids come true from seed. Unless you have a cutting/graft, you just get poncirrus seedlings, or lemons that freeze.