Ichang papeda is the most cold hardy species, besides from poncirus. That doesn't include hybrids.

Ichang papeda can survive on the border between USDA climate zone 8a/7b in the US South, while in more northern climates it can only survive zone 8a.

It seems like ichang papeda does not serve well in hybridizing program for cold hardy citrus. According to what Socal claimed, ichang papeda is barely survived in zone 7b/8a. I think it is as hardy as a citrangequat. If it barely survive then its hybrid would not be promising for cold tolerent ability.

Ichang papeda has an advantage though in that it does not confer any awful poncirus flavors to its offspring.

If I was breeding hardy citrus, I might make a cross with poncirus first, and then cross with Ichang papeda in a later generation. I think poncirus will require more generations of crosses to breed out the undesirable character traits.

Ichang papeda fruit is very sour, so I think it is only good for lemon hybrid. I tatste the pulp of a flying dragon poncirus fruit, and it tastes sourly like lemon but with some level of resin like residue. The outer of a fully ripe poncirus is fuzzy, hairy but very fragrant and pleasant that no other citrus fruit can compare to. I would like to carry that fragrance to poncirus hybrid. It does not taste great, but its fragrance can be used for something else.

Ichang Papeda comes from the region around the city of Ichang, China, thus it got the name Ichang Papeda. It taste like, and is used like, a lemon. It will grow where Satsumas can be cultivated.

Ichang papeda is much hardier than Satsuma mandarin.

It's true Satsuma mandarins can usually be grown in zone 8a, but that's in the South. I tried planting one in zone 8a in the Pacific Northwest, covered it with a clear vinyl plastic enclosure, with some gallon bottles of water under there, and while we did have a colder than normal winter, the Satsuma did not survive. (I'm thinking a Satsuma might be able to survive if you were in the middle of a large city though) My Yuzu trees survived though, and Ichang papeda is supposed to be hardier than Yuzu.

I did hear one report that Ichang papeda froze and died in zone 8a in France, right outside Paris, but that's pretty far North and maybe not so surprising. It was a colder winter than usual, and while his Ichang papeda froze to the ground, he said his Ichangquat (which is a hybrid between Ichang papeda and kumquat) survived and has been doing very well.

The difference, I am guessing, between Ichang papeda and Satsuma mandarin, is that Satsuma mandarins will suffer some damage whereas Ichang papeda can survive the colder or more northerly parts of zone 8a and come out unscathed.

I did talk to Nat Bradford (earlier this year) and he said a Taiwanica lemon he planted has been doing better than Ichang papeda. He planted them at his old home in Seneca, South Carolina. (He insisted it was zone 7a but I looked at a USDA hardiness map and the location seems to be more in zone 8a, maybe a little on the border of 8a/7b) He said he grew a Taiwanica lemon and an Ichang papeda outside there unprotected, and they have survived for 7 years. At one point he says the temperature got down to 4 °F. The Ichang papeda lost leaves and the leaves turned yellow-brown every Winter, but he says the Taiwanica did not lose leaves. The Taiwanica fruited for him, while he never saw flowers or fruits on the Ichang papeda. I specifically asked about the 2017-2018 freeze, and he said he had gone back to the property since then and saw that the trees were still there.

(This is the same Nat Bradford who is the great great great grandson of the original man who bred the Bradford watermelon, once a famed watermelon variety in the South)

Taiwanica lemon should not be as hardy as Ichang papeda, in absolute terms, but it is very vigorous growing, which perhaps explains why it did so well. Maybe the outcome would have been the reverse in the climate area where I am. (Also Taiwanica lemon isn't really a lemon, it's more like a sour orange type citrus, and doesn't taste that good)

Yes, socalnolympia you are correct, Ichang papeda is more cold hardy than a satsuma, and one can indeed test the absolute boundaries of where an Ichang papeda can possibly grow if they wish, then go ahead and plant the tree in such an area. However, if one would rather grow the Ichang in the locations where the tree will thrive at their best, then plant in the same cool locations that the satsuma can be grown in. Its up to the grower. I note that the vast majority of growers on this forum reside in locations that will nether permit either the satsuma nor the Ichang to grown outdoors. As always it is up to the grower. Have a nice day.

I'd estimate maybe around 15% of the US population lives in zones 9a to 8a, so would be candidates for possibly thinking about growing some of these varieties.

I just planted an Ichang papeda in the ground, so we'll see if it's hardy here.

Olympia, WA (climate zone 8a)

Olympia gets just a bit colder than Seattle in the winter.

my Yuzu has managed to survive the winter, losing half its leaves and suffering some bark damage, but put out a growth spurt at the end of July.

Really? Seatle is far north from Olympia. I am surprised to hear that it is colder than Seatle in the winter.

Is it a rooted cutting, Socal? I personally don't like rooted cuttings because I believe they would be several degrees less cold hardy than trees from seeds or grafted to poncirus rootstocks. I grew a batch of many flying dragon seedlings and got 1 extremely vigorous seedling that had its taproots growing like crazy all the way through bottom of the pot and digging deep into the ground. I carefully dug it up out of a 1 gallon pot to a 3 gallons pot and kept all the root system intact. Most of the flying dragon seedlings has shallow root system, but the only one that had the tap root as twice as the length of the upper part.

Yes, while it's true Seattle is a bit further north in latitude, Seattle sits right on the sound, and so the influence of all that water helps prevent the temperature from going down at night. Olympia, by contrast, sits at the very southern end of the sound, and so doesn't have quite as much influence from a surrounding body of water. Seattle has also built up a lot of development and paved surfaces, so that increases the temperature a tiny bit as well, being in the middle of a big city.

And yes, it is a rooted cutting. I took the cutting myself from a tree growing in Portland and grew it inside a warm grow enclosure under artificial lighting, so it could grow a bit bigger. Then I moved the container outside, in part shade, for a few weeks, so the plant could adapt to being outside, and finally I just put it in the ground.

For some reason this species currently seems to be extremely difficult/impossible to find from any retail plant nurseries.

I am growing some taiwanica x trifoliate (hybrid) seedlings for future rootstock that I hope will be almost as hardy as trifoliate but allow better compatibility and more vigorous growth of the scion. Especially important for Ichang papeda since it seems to be a rather slower growing species.

Of course, I'm really pushing the boundaries of what can grow in the ground this far North. It's still too early to say whether the Ichang papeda will do well here (though I'm pretty sure it will at least manage to survive).

Huyen, I have never heard, or red any publications stating seedling grown trees are any more hardy that rooted cuttings. Are you able to show your resources for your claim? I agree that seedling trees do have various benefits that rooted cuttings don't enjoy, but I don't believe that additional hardiness is one of them.

Jodi, I don't remmember where I've read it from. We all agree that the cold tolerant ability of citrus depends on many factors including tree health, virgor, gene...; however, by common sense, I also think that a healthy selective citrus seedling would have higher endurance compared to a rooted cutting which does not have a strong, deep taproot.

Thank you for your posts, but I don't think seedlings are any more cold harder than rooted cuttings. If seedlings actually did show greater cold resistance, that would obviously be a huge deal to growers and the citrus industry in general, as such it would be very well known and there would be a lot of written publications available.

Seedlings do often tend to grow taller and with more vigor since they're growing on their own roots. (no degree of incompatibility from being on a different rootstock variety)

I had previously had a theory that this might possibly translate into better cold hardiness, but from my limited trials in the PNW, zone 8a, this does not appear to be case, and the hardy varieties that were grafted onto trifoliate rootstock survived better than some of the ones grown from seed.

Occasionally you might have a seedling with a different combination of genetics from its parents that allows it to be slightly cold hardier, but this is rare.

I haven't trialed Ichang papeda specifically outside, so there's a chance it could prove an exception to the rule.

If you graft an ichang papeda cutting to an ichang seedling the grafted tree will grow like a mature rooted cutting but a seedling will reach for the sky starting at node count 1 vs node count 100 for the grafted tree despite it too is on its "own" roots

Jodi, even if it was the case then it would not have anything to do with the commercial citrus industry because commercial growers would only grow certain types of seedlings to serve as rootstocks. They don't consider seeds germination as a reliable propagation method due to its unstable and unknow outcome of the new seedlings. I also rarely see growers used rooted cuttings for their commercial citrus orchard.

Commercial growers dealed with cold damage issue in citrus by hybridizing with trifoliate poncirus or its hybrid or grafted to cold hardy rootstocks. Since commercial growers rarely used rooted cuttings but instead grafted trees, it made me more confident to believe that there would be some hidden reasons behind. By common sense, everybody would agree that rooted cuttings method is quicker and easier to propagate than grafting method since grafting usually requires 2 years old rootstocks and another year for the grafted scion to mature. In 3 years the rooted cuttings could have been a large matured tree.

Socal, I had no doubt that citrus on cold hardy rootstocks would be more cold hardy than on their own root. I meant the comparison in the cold hardiness between the same species grown from seeds and from cuttings.

Huyen Limh, thank you for your post As for citrus grafted upon a rootstock, and rooted cuttings, about 99+ percent of citrus trees are grafted. Rooted cuttings are just a fraction, less than one percent, mostly Meyer lemon.