The Tropical Fruit Forum

Poncirus aside, what other citrus varieties were native to mountains?

I do not really know but I don't think any citrus species are native to mountains. Poncirus trifoliata has been growing wild in the mountains of North Carolina though.

I think Poncirus polyandra might almost grow at what would be considered mountain elevation, though it is not very high. It rarely gets very hot there but also rarely goes below freezing, except at higher mountain elevations. Fumin county, Yunnan, China, where average daily highs do not rise above 68°F for half of the year.
This source says P. polyandra grows in forests on mountain slopes; at an elevation of around 2400 meters, southeast Yunnan (Funing).
Q. Ding et al., Acta Bot. Yunnan. 6: 292. 1984, not Citrus polyandra Tanaka (1928).
www.efloras.org , Rutacae
http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=107164

Even Khasi papeda only grows in the "hills" and not mountains, and the temperatures never get very cold in the Meghalaya part of India)

I tried growing seeds from fruits from a rootstock variety that had popped up, which I strongly believe was a rough lemon.
The seedling, which were grown to about 6 inches tall in containers were unable to survive a typical winter in Olympia, climate zone 8a, despite being on the deck only 5 feet from the house. It was a very vigorous grower though and did show some signs of mild cold tolerance, better than orange. 

The fruits were nothing anyone would want to eat, pretty bitter and low quality flesh, but pleasantly fragrant.

SoCal, I seem to recall that the trees you planted out were unprotected and were also quite small. I had read about the practice of growing the trees to a somewhat larger size before planting them out, so that the trunk itself is less likely to be compromised by freezing. Also, instead of leaving trees exposed directly to the cold, smaller trees could be protected.

Most of the plants were about 14 inches tall, almost as wide as tall. I did try to protect most of them a little bit, with a large bottle of water under them right next to the trunk to help resist freezing, and covered by a large paper grocery bag during the coldest nights.

I wonder if you tried to grow pure  poncirus seedlings as a control for your general agricultural capacities?

I have Flying Dragon and another Flying Dragon that appears to be growing up from rootstock. They both seem to be able to survive fine, but interestingly do not seem to be as vigorous growing as Dunstan citrumelo or Changsha. The Flying Dragon also appears to be deciduous and loses its leaves, whereas the other varieties only suffer leaf death if it is a colder winter than usual and more often (or often even then) not complete loss of all past leaves.
I believe the Flying Dragon from the rootstock originally came from Jim VH (another member in this forum) and is the one that doesn't have the normal awful poncirus flavor inside the fruits.

The plants may be only a little taller than 12 to 14 inches and grow slow. They seem like they will survive and slowly continue to grow over the years, but I think the other varieties will outpace them (if they can always survive).

I can quickly sum up my experiences in Olympia. Yuzu initially grows well and survives, but can sometimes decline after 2 or 3 years and finally die, apparently not having the energy to recover after another winter. But Yuzu can seem to grow well if planted in a very optimal and protected warmer spot in more urban surroundings. The decline seems to begin after some moderate damage from a colder than normal winter (which comes along about every 3 or 4 years).

Keraji was not able to make it for me, even though seeming to survive well through one winter, even though it was protected and planted in an optimal spot. Bloomsweet was not able to make it. Sudachi was not able to make it, even though after one year it seemed nearly as cold tolerant as Yuzu, but it was planted further away from the house in a spot that might have gotten colder.

So far a Dunstan citrumelo bush is doing great.
An Ichang lemon appears to be surviving outside, in a protected spot, but I am not sure for how long, whether it will be able to recover after the next winter and not decline. It seems to suffer some obvious damage and die-back of some of its branches in winter but has recovered well with vigorous leaf growth.
A Changsha mandarin, in a protected spot, appears to be doing great and is very vigorous. 

Kumquat seedlings that had grown about 10 inches high were not able to survive.

Two Ichang papeda plants have both died and did not seem to be able to survive the cold. They were not on rootstock and were planted futher away in a spot that may have gotten a little colder.

One Ichangquat seedling survived through one winter and appeared to be doing great but died after the next winter. Another Ichangquat seedling was killed down to only one inch above the ground and the plant was not able to send out any leaf growth for the year after that. I expect it might just slowly decline and finally die.

Ten Degree Tangerine (a hybrid of Yuzu and Clementine) lost all its leaves and was not able to regrow them the following year, although the plant seemed to send out just a few buds of leaf growth. It slowly declined and finally died 2 years later.

I've tasted the fruits from an Ichang papeda tree, and have tasted kumquat and various kumquat hybrids - calamondin, mandarinquat, and Thomasville citrangequat.
Based on that, I would imagine the rind of Ichangquat might be a little similar to mandarinquat, in terms of edibility. That is to say you could certainly eat them, but they are not really exactly as enjoyable and delicious as a Meiwa kumquat.

The rind of Ichang papeda is edible, in my opinion - interesting but maybe not the most enjoyable. It's a little like the rind of citron, noticeably easier to eat than the the rind of lemon.

I'd imagine the Ichangquats probably have some lime-like flavor as well. Thomasville citrangequat does, and to me, the Ichang papeda I tasted sort of had a flavor halfway between lime and lemon, I would say. The rind of Ichang papeda does have just a little bit of "skunkiness" and bitterness but is not really that bad (the skunkiness you would not notice unless you ate a larger amount of it).

I had the premium Yuzu from Japan and candied the peel. When I looked up the process of candying citrus peel it often said to boil the peel to remove the bitter flavor. Because I've heard sometimes that Yuzu peel is not bitter, I did not do this, as I wanted to not lose any flavor by boiling them. But the result of the Yuzu candied peel still tastes bitter. It might be less than most other citrus, I can't compare as I've only candied Yuzu for now.

Was your Yuzu fresh and the peel tender? To use the Yuzu peel, the Yuzu should be fresh and the peel bright yellow-orange in color.
If you bought your Yuzu from a market, outside of Japan, it may have been picked unripe and greenish in color.

At its best, Yuzu zest does have a tiny bit of bitterness, but less than lemon peel.

One of the historic Japanese Citrus varieties ( sorry can't think which ) is said to have been grown from a fruit found on the beach several hundred years ago.

That would be Natsu mikan (meaning "summer mandarin orange", though despite the name, closer to being grapefruit-like rather than mandarin orange). I have actually picked off the tree and tasted one (which I described in another thread). I do not believe this variety has any ancestry from unusual citrus species though.

Something I had overlooked in a different thread.

This may not be completely correct, but from what I understand C. ryukuensis is kind of like a purer ancestor of C. tachibana.
In any case, they are probably very closely related.

Is Taiwan far enough off-shore to be genetically isolated?

I think it would be very difficult for species from the mainland to reach Taiwan by natural means, perhaps not impossible. Most likely any original citrus species that were brought to Taiwan were brought there by humans - the Chinese. (With the exception of C. tachibana which was probably indigenous to either Taiwan or Southern Japan, or perhaps both)

The island of Taiwan is 160 km (about 100 miles) away from mainland China. And probably most of the citrus types did not even exist on the coast of China in that area before the Chinese civilization came, with the exception of kumquat.

There are about one thousand endemic plant species in Taiwan, meaning they exist only on Taiwan, not the mainland. So this would seem to indicate some degree of natural genetic isolation.

According to one ancient text, mandarin oranges could be found growing in the wild on the island of Hainan by around the year 1000 AD, though it is unlikely the species originated there. (Edward H. Schafer, Shore of Pearls: Hainan Island in Early Times, University of California Press, Berkeley, 1970 )
They probably escaped into the wild from human cultivation.



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

(It should of course be noted than Nansho daidai was already a cultivated variety in Japan in old times, before being found by the Japanese botanist growing in the wild in Taiwan. It was valued in Japan as an ornamental because the fruits continue to hang on the tree for a long time, sometimes up to several years)

I am not saying this is applicable to all climates, but from what I have seen in the climate where I am, from several Yuzu plants, maybe about 11.5 degrees F ( -11.35 degrees C) might be the limit of what Yuzu can survive, over consecutive years. At 14 degrees F ( -10 degrees C) it will suffer virtually no damage. Below that it will suffer some partial damage. The plant might be able to survive down to 10 or 11 degrees F with serious damage, but will not be able to sustain that year after year. Not in this climate. Maybe somewhere farther South in the U.S. with a longer and warmer growing season it might be able to recover and not slowly decline from that.

My Dunstan citrumelo appears to have more cold tolerance than my Yuzu and can survive better. The leaves will be more likely to fall off, but they can regrow easier. Yuzu does not regrow leaves as well. It's important that the Yuzu keeps its old leaves because it might only grow 30 or 40 percent the number of new leaves the following year as the number of old leaves on the tree. The leaves do appear to be able to recover from partial damage, and can regain some of their green coloration, but if damaged beyond a certain level, they will eventually fall off, often this may not become fully evident until later when things begin warming up.

I would like to point out that these numbers are really not exact, and are more based on my subjective impressions and instincts I have gathered from experiences, with several plants over several years. So I hope that just helps give some anecdotal idea, rather than being taken as exact reliable information.

The Ichangquat I have should be the same one as Ilya's, which for him has survived unprotected in zone 8a for 15 years or more (I don't know exactly when he got it). Which included temperatures down to -16°C I believe (3.2°F).

It seems the Ichangquat cultivar 6-7-2 is the one that is most cold hardy, while others aren't as much. Although the one we have in Europe is an F2 from 672, so I'm not sure how the US and EU versions of 672 would compare.

Yes, the seeds came from Ilya, but one thing to consider is that Ilya's tree is growing in a very protected spot on the inner corner of two high walls of his house. 
Another factor might be the climate. I suspect there may be something a little bit different about Europe (specifically France's) climate compared to the U.S. PNW. Although the PNW region and France are very similar, zone 8a in Europe may translate to more stable temperatures with fewer ups and downs than in the U.S. I am not sure. It seems many have had more success with varieties in zone 8a Europe than I have had with those varieties here.
Ilya also lives not too far from Paris, which might further be helping, preventing things from getting too cold.

What kind of temperatures did you have when your plants got wiped out?

It went down to almost 12 degrees F, maybe only 14 degrees F (let's say -11 degrees C ),  buried in a foot of snow.
This was preceded by a clear sunny day. Perhaps the sun is a little bit more intense here than in Europe, and that is enough to warm the leaves too much, maybe reducing the level of protective dormancy? The latitude on the planet is not much different (47 degrees north here compared to 48.8 in Paris, which could still make some significant difference), but perhaps the skies here can get a little bit more clear sometimes than in Europe during the winter. I am not sure, it is very likely I am just overthinking this.

Some varieties that seem like they may be able to make it here gradually decline year after year until they finally die.

I tasted the Morton citrange and Thomasville citrangequat that Jim VH grew. (We think it is a Morton citrange because the fruit strongly resembles it and does not resemble any of the other hardy citrus varieties we are aware of, and the nursery where the tree was bought used to sell Morton citrange and we believe there could have been a mix-up) 
The Morton citrange looks like a delicious orange, few seeds, but has a terrible poncirus taste inside that makes it completely inedible, to me in my personal opinion.
The Thomasville citrangequat was completely edible, in my personal opinion, with little bitterness and barely any detectable poncirus off-flavor. The flavor was rather lime and calamondin-like, but a little inferior in flavor to a regular lime.

I think Citrangeremos are hybrids between Eremocitrus x Citrange.