Did you know the Chinese city of Yichang, in the region where the Ichang papeda is believed to have originated, is just a tiny bit further south in latitude than San Diego? That area of China gets most of its rain during the Summer. It doesn't have much elevation, but it is pretty far inland so can still get cold in the Winter, equivalent USDA climate zone 8.

So warm most of the year, not too extremely hot and dry during the Summer, Summers can still be fairly humid, this is exactly the sort of weather citrus likes to grow in (except for the colder Winters).

While they are separate species, the papedas are believed to be more closely related to each other than to other citruses. C. micrantha (ancestor of lime) and Khasi papeda (C. latipes, the ancestor of Kaffir lime) both have symmetrically large winged petiole leaves like Ichang papeda (C. ichangensis). Ichang papeda is also believed to be closer in genetic relation to citron and pomelo than to mandarin. However, unlike C. ichangensis, C. micrantha and citron are both very sensitive to cold, more so than orange. Since Kaffir lime descends from a different species papeda than real limes, it can grow in zone 9 (even saw one source that says it can survive down to 15F, not sure if that's true).

(People most often don't eat the fruits of Kaffir lime, but rather the leaves of this citrus are really good for adding flavor to Thai cooking recipes)

Changsha mandarin is either an indigenous species in China extremely closely related to mandarin, or became naturalized in the wild a very long time ago. There are several different cultivars of Changsha that evolved to be suitable to different growing conditions in different areas. There was one study, looking at genetic markers, done on an accession of Changsha mandarin which indicated it was mandarin but may have had up to 15% pomelo in its ancestry. (Genomics of the origin and evolution of Citrus, Guohong Albert Wu, Javier Terol) This could possibly be from genetic introgression over time from surrounding cultivated hybrid mandarin varieties.

Stan McKenzie sent us a picture of a large Changsha tree on his citrus farm in Scranton, South Carolina, that he said had survived a drop all the way down to 8 F degrees on January 18 this year, and it was full of fruits by November 5. (I think normally Changsha trees can only survive down to about 10-12F)

Here's the picture:

The fruits are filled with seeds though.

Changsha mandarin is also notable for its drought tolerance (since it comes from a drier farther North area of China).

Also for any of you who want to see pictures of what Kunenbo in Japan looks like, you can see them here:

https://archive.org/details/kunenbo-Japanese2

Interesting documentary about Yuzu from Japan some of you may be interested in:

https://www.youtube.com/watch?v=jdUq2AVLEn8

Yuzu is a surprisingly hardy citrus. I heard someone got a tree to produce in Seattle. They got it to the point the tree was surviving unprotected next to a parking lot.

The first time I even heard about Yuzu, I was going to a favorite Japanese restaurant (closed now, but very authentic, run by a Japanese couple who didn't speak English very well) and there were corporate advertisement notices on all the tables for a special alcoholic cocktail drink made in Japan that came in three flavors: Grapefruit, Lemon, and Yuzu. I asked the Japanese woman what it was and she said it was very hard to explain, after struggling for a few seconds to think of what to say, she said it was like Japanese Lemon, but looked a little hesitant about her answer.

Years later, I finally found a nursery that carried Yuzu trees. Those things are quick to began producing fruit even when very young, and produce fruits very abundantly. But the trees can also produce thorns four inches long that could pop a tire (I'm not exaggerating). The thorns are so long they're easy to avoid if you are attentively watching what you are doing, but if you're being careless it could be easy to get poked!

Thanks for the good info. I picked up a baby grafted changsha from Stan this summer. It hasn't grown much since I potted it up. Unfortunately, I don't think it would survive inground here, though I might graft a branch onto FD rootstock and give it a try once my little guy grows up and can donate to the cause. I'll probably stop back by Stan's after the holidays and see if he has anything interesting.

I don't think it's likely to survive there. Although it might if you're willing to give it some protection every Winter.

You might ask Stan for some fruits of US 852 - a hybrid between Changsha mandarin and trifoliate. Those can survive zone 7, and don't taste too extremely terrible (at least compared to trifoliate). The fruits are loaded with seeds so you only need one fruit.

Alternatively you might be interested in seeds from this unusual hybrid: https://www.ebay.com/itm/Citrofortunella-x-TRICIMEQUAT-Cold-Hardy-Citrus-Tree-SEEDS/362495154487?hash=item5466651937:g:kn8AAOSw~T9b-xay:rk:2:pf:0

It's supposedly a (Hong Kong kumquat x (kumquat x lime)) x trifoliate hybrid, which is "hardy to at least 7b ". He claims there is no bad taste from the trifoliate.

He's named it "Tricimequat".

A lot of good information, thank you!

one of the little Keraji mandarin seedlings I'm growing:

not growing it because it's a particularly good variety of mandarin, but it is kind of rare, and is cold-hardy, even more so than Satsuma, mature trees may be able to survive all the way down to 12-14 °F.

I suspect it may hold potential for future breeding.

Does anyone know where to get an improved variety of changsha mandarin? I've read there are a few cultivars out there, one of them being 'Honey' but I've not seen them offered in the US