Apparently one reviewer on Daves Garden said of aurantium Seville that it does fine in zone 8a.

Also I just read about a perhaps rare variety Masagno (but the UC Davis germplasm does not have it-no clue where to find) that may be suitable...

Also Dr. Litwinski discovered in Massagno in
Switzerland a Sour Orange (Citrus aurantium),
which survived all freezes in Norbert Dörrs
Backyard. The cultivar clone has no name, so he
named it about the discovering place: Citrus aurantium âÂÂMasagno

(http://www.steffenreichel.homepage.t-online.de/Citrus/lime8.pdf)

https://sites.google.com/site/mrtexascitrus/?pageDeleted=%2F36belt
http://mrtexascitrus.weebly.com/

I have found sour orange to be similar in hardiness to satsuma. But where I live, SE Texas is not
a stretch for satsuma.
phil

Thank you so much. Low has been 10-15 degF last two winters here,

For my uses, do you recommend I should give Seville sour orange a try against wall with tarp and hope for best or try one of these hybrids?

All I need is nice sour juice and fragrant flowers, I dont need any sweetness this fills the role of lemon/lime, but I don't want astringency, dry fruit that lacks juice, golfball tiny fruit... Seville is a nice fruit for its purpose of supplying sour juice. Like a trifoliate I guess but a million times better, more like a lemon.

10-15F is not citrus country. You will need to protect for any edible citrus to survive.

The only citrus that will likely survive (and possibly fruit) in zone 7a with minimal or no winter protection will be Poncirus or one of the tougher Poncirus hybrids. Odds are that a Seville (even in an excellent microclimate) in zone 7a will not make it through winter with only frost blankets/burlap for protection. You could certainly plant one outside, but it will need good protection (I have a satsuma outside in my zone 6b/7a location but it receives substantial winter protection)

You will also need to consider when the fruit are ripe. Seville are ready to use in spring/summer therefore the fruit need to be overwintered on the tree. Thus you would need to prevent the fruit from seeing temps below 28F or so for any prolonged time.

If you want something that requires limited winter protection and will possibly have useable fruit before winter sets in, your options are pretty slim (Poncirus or Poncirus hybrids).

Having said that, you can grow pretty much any citrus outside in zone 7 or colder, it just depends on how much winter protection you are willing to provide.

Seville oranges are grown in sevilla spain. if you to wunderground.com and enter sevilla spain - then look at weather history : enter smth like jan or feb.
you'll see that it barely goes below freezing (32F). you can see actual temps for many years - compare it to yours and you'll have a very good idea if it can survive.