Arctic frost and orange frost go into single digits. Marumi kumquat down to 0F. sitsuma prague may hit -2F and they all taste good.

Ten-Degree Tangerine aka Clem-Yuz 2-2 or Clem-Yuz 3-3

I’ve not heard of that one, but Steve knows his stuff. Steve, I have a Prague citsuma from Stan. Should I plant it in the ground this spring?

Plant the Prague in ground. put a fence or something to protect it from children.

Steve

Lol Steve...most important, keep it away from my massive, fluffy puppy. I’ll plant it this spring then. Lucky, even though my zone is technically 7b since right off the bay, it seems colder than NC. We were just there looking at Elon. I’ll plant it though and let you guys know how it does. Adam, Stan McKenzie is great and very knowledgeable. He should be able to give you great advice for your area.

Nansho dadai is similar to a sour orange. (By that I do not just mean an orange that is sour but a certain variety or family of oranges that most of you are probably not familiar with. One variety was used in making perfume and one variety is the traditional orange that was used to make marmalade)

Probably very poor quality for eating compared to any grocery store citrus, but it can be eaten, and probably could have some culinary uses.

I am in WA state and know a few things about trying (mostly attempting without too much wonderful success) to grow hardy varieties of citrus here. I very much doubt it can survive 5 degrees F here, especially in this climate, but maybe somewhere between 10 to 12 degrees might be more reasonable.

Regarding flavor, this article may be of interest to you:

Forestry Bureau held a "Return of the Nansho Daidai Sour Orange" event at the hiking trail entrance of the Daping Forest Road of Jiali Mountain in Nanzhuang Township, Miaoli County. Planting of the Nansho Daidai Sour Orange took place at the event, where it was also pledged that this citrus species will be brought back to its place of origin (this citrus, named after Nanzhuang, is an endemic plant of Taiwan and is now on the verge of extinction in the wild). It is the hope that this act can help restore the forest ecosystem in the foothills of Taiwan and promote the development of green economy in the mountain village communities.

The Nansho Daidai Sour Orange (Citrus taiwanica Tanaka & Shimada) is a citrus species in the Rutaceae family endemic to Taiwan. It was first documented that the plant was discovered in 1926 by Japanese botanists in Miaoli's Nanzhuang Hongmaoguan, present-day Penglai Village in Nanzhuang Township, and was therefore named "Nansho Daidai Sour Orange." However, with the development and utilization of the foothill forests, the Nansho Daidai Sour Orange almost become extinct in its original discovery site, and it has been listed in the IUCN Red List as a Critically Endangered species due to its rarity.

The Penglai region in Nanzhuang is the traditional living area of the Saisiyat people. According to Gen Chih-You, a Saisiyat elder, the Saisiyat name for Nansho Daidai Sour Orange is gadayou (meaning "food prepared by mother"). The citrus has been an important plant for the Saisiyat since ancient times, since the fruit is both a snack and also has medicinal and ceremonial applications. Elder Gen recalled that when he was a child, whenever he had a cold, the family elders would grind dried Nansho Daidai Sour Orange into a powder for him to take as medicine. It was a must-have plant for general healthcare used by every Saisiyat family in the early years when medical treatment was not readily available.
According to the Forestry Bureau, the fruits and leaves of the Nansho Daidai Sour Orange have a strong fragrance, while the juice has a distinctive sour taste and a slight bitterness. The fruit's unique flavor makes it very suitable for processing and consumption. Furthermore, the wood of the orange tree is extremely fine in texture, and according to literature, it was considered the best wood for making pipes, knife handles, and other delicate wooden tools in the early days.

The fruits were tested for the development of essential oil extraction, dessert-making, and tea and beverage preparation, all with amazing results. At the event, the Hsinchu Forest District Office presented a "pound cake with Nansho Daidai Sour Orange frosting" made using the juice and "Nansho Daidai Sour Orange peel nama chocolate" made using the orange peel syrup. The unique refreshing scent and tangy sweetness of the Nansho Daidai Sour Oranges greatly impressed the guests who tasted the delicious treats. It is hoped that the local tribal communities of Nanzhuang will create specialty products with Nansho Daidai Sour Oranges, as it would not only help with both species preservation and the economy, but also bring a wonderful flavor experience to the people of Taiwan.

"Return of the Nansho Daidai Sour Orange": Forestry Bureau Partners with the Saisiyat to Restore Taiwan's Endemic and Rare Plants
from Taiwan, January 29, 2021
https://www.forest.gov.tw/EN/forest-news/0067054

Apparently there is a Taiwanica (Nansho daidai) tree that has been doing very well, producing lots of fruits, at the Georgia Southern University Armstrong campus in Savannah. It's at the corner of Arts Drive and Library Drive outside the Science Center. At least according to the USDA climate map, Savannah is in zone 8b.

Citrus taiwanica (wsav.com)