The Tropical Fruit Forum

seeds from special variety of poncirus trifoliata that has much less bad flavor. (Probably comparable to "Poncirus plus")
doesn't taste extremely great, and is full of seeds, but very little of the typical and characteristic type of horrible flavor usually found in poncirus. Most poncirus hybrids have more of the bad flavor than this.
sort of has a poor quality mandarin, grapefruit, and pine flavor, but sour and acidic.

I have no doubt if a hybrid were made from this it would be almost completely edible.

It's Flying Dragon form, but about 2 in 10 seeds turn out to be the straight growing form of poncirus.

start October 21


will send 4 seeds for free, but $5 to cover shipping cost

It looks like a European dessert plum variety.

I've tried "President", which are pretty big, but not quite as big as that. They are good. Better than the smaller prune plums. (And I read that President is more of a firmer canning variety and does not have the best taste, but I would still rate them somewhere between an 8.3 and 9.2 out of 10 )

This family of plums doesn't really have a "good" name, but they are the most classic category of European plums (which is probably why they do not have a specific name, because in older times this is what first came to mind when most Europeans thought of a "plum"). They were sometimes referred to as "sugar plums" (think of Tchaikovsky's "Dance of the Sugar Plum Fairy").

You may wish to try to use Musa sikkimensis in your hybrids.

I just tasted Flavor Grenade pluot at a farmer's market and can report the flavor.

It tastes very good and enjoyable, but falls short of "fantastic" and "amazing", in my personal opinion. It's sort of not very "memorable" or only just a little bit memorable (to me).

It has plenty of sweetness, and a little nice tartness to balance out the plum flavor (though much more sweetness and less tartness than other plums or pluots). So it has the basic parts of a good plum flavor: the combination of sweetness and plum-like tartness. But it just seems to be a little lacking in special plum flavor and aroma (it doesn't have much of the "sharp" aroma of plum). It doesn't really have the same level of intensity of flavor and perfume as some other pluots I've tasted.

In consistency, it seems very "meaty" (almost a little like apricot) but at the same time very succulent and juicy as well. I think the inner consistency (or texture) will appeal to people who like ripe peach and mango.

It is full of "flavor" in one way (very sweet, just enough plum tartness to be able to balance that out, and also a little mild apricot flavor added in), but also lacking in "flavor" in another way since it is not very aromatic.

Your best bet may be to try to grow Yuzu from seed. It usually grows true to seed. And in fact in Japan, Yuzu is sometimes used as a rootstock.

The plant will need to be protected and probably brought inside during the first or second winter when still small. Maybe after it grows 32 to 55 cm tall, it can be left outside during winter.

Some may find my speculative thoughts annoying, but I'd like to present a personal theory I have about the genetic ancestry origins of Green Gage Plum.
This is just based on some very general knowledge I have about plums and plum morphology.

I think Green Gage plum most likely originated from a cross between a Mirabelle type plum and sour green Persian plum (Prunus vachuschtii).

Prunus vachuschtii is native to the countries of Georgia and Azerbaijan, and is a very popular plum in Persia, and is also commonly grown in other parts of the Middle East. In Lebanon and Syria they are called Janerik. It's not a sweet plum, but is nevertheless enjoyed as a refreshing snack (often with salt, or a flavorful sauce, or as the main ingredient in a sauce). I have tasted them.

Prunus vachuschtii is more of a tentative species name for this plum variety and is not universally recognized.

I think this cross most likely happened in Italy or another country across from the Adriatic Sea from Italy, which has a lush forested climate similar to the Caucasus region, where plums grow very well. (This might make sense because these countries were at a cultural border zone between Europe and the Middle East region, under the Ottoman Empire at the time)

Mirabelle plums most likely derive most of their ancestry from Prunus brigantina. But likely also have some ancestry from "Prunus domestica" (I mean what is known as the "Italian prune plum"). I believe Prunus brigantina may have resulted from hybridization between Prunus cerasifera ("cherry plum") and apricot, or represents a species intermediate between these two other species.

In fact I believe there are many "subtypes" of Prunus cerasifera that probably have some genetic introgression from Prunus brigantina, because some varieties of Prunus cerasifera have a very orange color (orange-yellow, but almost more orange than yellow) and have a strong aroma kind of reminiscent of apricot. (I have tasted such fruits from a wild tree)
This might help explain the low chill requirement of Prunus cerasifera, which has even been able to become naturalized in the wild in southern Australia.

(Prunus domestica would have come from a complex process of hybridization between Prunus cerasifera and Prunus spinosa)

Chemically, I believe the distinctive "green" aroma and flavor primarily comes from esters of 2-methylbutyrate. But also just a little bit from cis-3-hexenol (smell of grass). 

Sour Green Persian plums do sort of have what could be described as an "exquisite" plum aroma or flavor, but it's specifically the very dry "textured" smell of plum (concentrated in the skin), rather than the "fruity" smell of plum. (The part of smell I'm attempting to describe, probably more of a terpene or terpenic, "woody", very important component in the smell of plum, clearly identifiable and recognizable as the unique characteristic and distinctive smell of "plum", despite lacking any fruity or "sweet" qualities)

Very quickly, usually how number of chromosome sets work is an offspring gets half its number from each parent. So, for example, if one parent had 2 (diploid) and the other had 4 (tetraploid), the offspring would have 3. But if the offspring has an odd (uneven) number of chromosome sets, its seeds will (in most cases) be sterile (unable to grow). In less common cases, sometimes a parent with an odd number can sometimes contribute its chromosomes in an "unreduced" form to the gamete (sperm of egg cell). So one parent with 3 sets of chromosomes might in rare cases contribute all 3 to the offspring, while 1 other chromosome set comes from a diploid parent (which is normal), resulting in a tetraploid (4) offspring. In rarer cases than that, it's sometime possible for the chromosome number in a species to spontaneously double. (This can be intentionally induced in plants with the use of colchicine)

I would guess the issue is the soil. I have made the change to avoid organic matter in my soils
...
My citrus are in basically rocky soil with decomposed granite, pummice and other stuffs like sand. I might have put some peat moss in.

I want to point out that the type of soil that should be used for potted citrus probably differs very much depending on what part of the country you are in.
On the U.S. West Coast, you want rich soil that will retain moisture well. On the East Coast, you want soil that can drain well and not result in too much moisture build up or waterlogging.

In climates with hotter summers, it's possible the plants are getting too much full sun. This can create water stress on them, and the roots may not be as capable of providing the larger volumes of water due to the more limited root space in containers. This should not be taken to imply that the solution is just to give the plants more water, since that can cause problems.

There are some "cold hardy" citrus varieties for zone 8, if that counts as "tropical fruit". I'm in zone 8a in Olympia, WA (U.S.) and am growing Changsha mandarin, Yuzu, and Dunstan citrumelo without protection. They are not covered.

Some might consider figs to be kind of "tropical", or at least subtropical. There is almost a whole world of figs, many interesting varieties, different flavors.

You can also research the field of banana breeding. Back several years ago I was trying to cross Musa sikkimensis with one of the more cold tolerant edible bananas. Theoretically the resulting hybrid would be able to survive in the ground in zone 8, but would need a temporary greenhouse covering in early spring (but not winter) to give it a good start. The plant would most likely die to the ground most years in zone 8, but would regrow each year. 
That might be far too much work and investigation for you, however.

While not exactly tropical, there are some more "unusual" fruit, such as quince. Maybe Russian varieties of pomegranate, especially if you have enough heat during the summer.

In my opinion, it's probably a good thing to keep the tree in a container for the first one, or even two years (provided the container is big enough sized to provide adequate root space, and you are using the proper type of soil, and willing to consistently water).
I mean keeping the tree in a decent sized container and allowing it to grow some size the first year will make it more likely to survive.

But remember that these plants in containers definitely should not get full sun if they are out in the open.

The tree will have to go in the ground at some point, because when the plant gets big enough the roots will need much more room. By year 2 or 3, it should go in the ground. (A very large half wine barrel might allow you to extend that to 4 years, though I don't think I see a point if you eventually intend the tree to go in the ground)

You mentioned that when you did get fruit (after 9 years!!) it was on the minnie royal. Did you also ahve a royal lee tree at that time? If so, it seems my idea of purchasing a royal lee as a companion tree might not work out to well.

I got a little bit of fruit on the two Royal Royal Lee trees, but it was more like only 4 fruits on each of the trees.

Likely after another one or two years they may produce a little more fruit, I think. The trees are still not really a huge size. The tree growth appears to be slower in a climate where the trees do not get adequate chill. I think tree maturity will help a little bit to counter the reluctancy of the tree to produce fruit.

From what I understand, Royal Crimson is practically the same as Royal Lee except for being self-fertile (not needing a separate pollinator).
It is likely that helps because if the tree is so reluctant to produce any fruit, then pollination becomes much more important. With a self-fertile tree, the same flower can pollinate itself, often without any bees present.

The Royal Minnie Lee had "countless" fruits (although a very small size without the thickest layer of flesh, but still possible to snack on) and was more generous.
I can share that the Royal Minnie is grafted onto the very top of a big Bing cherry tree, which has so far not produced any fruits, despite the fact that the bottom half gets much more shaded during the winter time which I would have expected to help.
It's also obvious that the Royal Minnie branch is growing significantly faster (in width and branching) than the Bing trunk it is grafted onto, but the graft seems to be holding.

Black Tartarian is an early producing variety, and is supposed to be a great tasting variety, but it will not work for you in your climate, since it is not a low chill variety. Royal Minnie Lee is very early flowering as well, probably more early than Black Tartarian I would imagine.

I would also like to ask you, since we are in the same growing region, given the length of time it can take for these trees to produce fruit in our climate, is pruning likely to delay fruit production even more?

I don't know, since I never pruned, since the trees never put on huge amounts of growth. Definitely not fast growth in this climate.

If I had to guess, probably pruning would cause a moderate setback for the tree, but the growth of the trunk and roots may be more important, so long as the tree has sufficient leaf cover. In this climate, once the tree begins to develop some canopy, I think the tree will do better, since leaves help shade each other, helping to prevent excessive sun exposure on each individual leaf.
It may also be possible that if you allow the tree to gain some size and then prune it right when the buds are just beginning to form, it might even help encourage fruit set. I'm not sure.

Do you have any suggestions about how to keep the tree smaller without risking delaying fruit production even further, or is this the sort of tree it's just best to leave to its own devices?

I do not know. But one thought, if you do not want the tree to grow too tall but do not want to set back its growth too much, is to immediately trim the top tip of the leader branch. Usually when the tip of a branch (or the top of the main trunk) is cut, the branch stops growing in that direction. This would theoretically allow the tree's energy to be diverted to other directions of growth.


This may sound odd and crazy, but I think one think that will help your tree, especially at this stage, is to build a sun shade screen, to help filter the light and reduce sun exposure. In this climate, even with 70% shade cloth, the leaves would still receive enough sun. That will help contribute to lusher healthier leaves and theoretically faster growth.

I also want to point out that any cherry tree, even the special "low chill" variety you have, will likely be challenging in zone 10.
The sun exposure may likely be difficult on its leaves, and you will probably have to wait many years before fruit production begins. And even then, the tree likely will not produce fruit as abundantly as it would in a zone 9 or 8 climate.

I planted several of these in zone 10 (on the border of 10a/10b) and it took about 9 years before it produced fruit for the first time (that was just this year), and most of that fruit was only on the Royal Minnie, which has even smaller fruit size than Royal Lee so is usually considered to be a "pollinator" tree rather than the main tree a grower would be anxiously awaiting fruit from. And it was a cooler winter than usual that did not heat up in late February, which is not the norm, so that no doubt had something to do with it too.

It's not totally impossible, but you will need to be very patient and take very good care of your tree.

For added pollination, it is always possible you could graft in a different cherry variety into the tree, but it's advisable to choose another low-chill variety (there aren't many to choose from) to optimize chances that the bloom time will overlap. That could be another discussion.

I've noticed my poncirus here tends to put on growth flushes when its hot. I do wonder if poncirus needs a fair amount of summer heat, even though it's cold tolerant.

My hardy figs act like that, too.

I was thinking about commenting in this thread, but waited until now.
I was reluctant to post anything, afraid it would be off topic, since my observations come from the growing zone in the Pacific Northwest.

In the Pacific Northwest, which gets much less cold than Michigan, but has a growing season which is very slow to heat up, I've noticed that many poncirus hybrids have no trouble surviving the winters here, but just have trouble putting on much growth the rest of the year. In fact I'd almost say that Yuzu almost seems to grow "better" here than poncirus hybrids, even though Yuzu has a fair chance of suffering severe die-back (or even slow decline over 2 years and eventual death) if not planted in an optimal spot.

I have a US-852, a tiny plant, that is surviving in the ground here, but almost doesn't seem to be putting on any growth. After more than 3 years. Not just one plant but several seedlings in containers outside. I suspect it may be due to the lack of a long enough growing season with enough heat. Yuzu may be much more vulnerable to the winter cold here, but puts on a much faster growth rate. Same thing with Changsha mandarin. Though I think for some reason pomelo, grapefruit and orange genes seem to contribute to faster growth rate in poncirus hybrids, despite being more "heat-loving".

I do not have experience growing them, but higher end super markets sell them in jars. It is by far the best tasting of the commercially available olive varieties I have tried, in my opinion. Though that may not be saying much.

Now you're making me hungry. Just by coincidence I happen to have a jar of them in my refrigerator right now.

I did some in depth online research into this years ago. I can't remember all the details, but can share what I remember (though my memory can be wrong).

There was some research to suggest that Poncirus polyandra was likely more like a subspecies of Poncirus trifoliata, so probably is not as unique as some may hope for, and moreover, given the growing location, probably had less cold tolerance than Poncirus trifoliata.
So from the details I was able to pull up, it seemed it was probably not promising.


But I can provide some details that come from the Kunming Botanical Gardens website in China.

I will provide a translation.

"P. polyandra is an endemic species of Yunnan that was first discovered in Fumin County, Yunnan Province in 1984, and is a precious citrus breeding germplasm resource. The fruit can be used as a substitute for orange husk for medicine, and the locals call it "cough tree". The investigation found that Fumin orange has become extinct in the place of origin, and only one plant has been artificially cultivated in a village near the place of origin.

Researchers at the Kunming Botanical Garden began to collect seedlings and ex situ protection research on Fumin orange in 1993, and have successfully protected 8 Fumin orange plants ex situ, of which 5 have bloomed since 2008 and bore fruit in 2012 More than 30 were harvested, and more than 200 seeds were harvested, laying the foundation for the return of the native land and population reconstruction of Fumin orange.

Since mandarin orange (橘 ju) and trifoliate orange (枳 zhi) are two different types of plants, of course the genes of the two cannot be the same. ... The saying "southern orange and northern orange" actually stems from the misunderstanding caused by the ancients' poor observation and lack of scientific verification."

http://kbg.kib.cas.cn/wzbh/jxzq/202003/t20200310_598617.html

"
[picture of fruit shown below]


image caption: The fruit of the Fumin trifoliate orange P. polyandra looks a bit rough, resembling Zhang Fei (rough looking character in the classic story Romance of the Three Kingdoms).

     The Fumin trifoliate orange is a nationally protected wild plant, endemic to Yunnan and found only in Fumin County, Yunnan Province. Because of its thorny branches, it is called the "thorn tree" by the Miao people of Fumin. Its fruit is bitter and inedible, but locals use its leaves and branches to treat coughs and rheumatism. Its active ingredients may have antioxidant, skin-whitening, and anti-inflammatory properties. Its cold tolerance and strong tillering ability make it a suitable rootstock for citrus, accelerating ripening and dwarfing citrus trees. Furthermore, hybridization of the trifoliate orange with the sweet orange (C. sinensis) has resulted in the cultivar P. trifoliata  x  Citrus sinensis . It is unknown whether the Fumin trifoliate orange can be hybridized with other citrus species to develop new varieties.

       The Fumin trifoliate orange was discovered over 50 years ago. Because it was found in Fumin County, it was named "Fumin trifoliate orange." Because it has significantly more stamens than the trifoliate orange, its specific epithet is "polyandra," where polyandra equals "poly" (many) and "andra" (stamen). Over 50 years ago, a valley in Fumin County boasted a large population of the tree. However, within 20 years, only 15 trees remained. A decade later (by 2008), the tree was completely extinct. Fortunately, botanists, besides hiking and writing, also enjoy planting trees. Eleven Fumin trifoliate oranges have been planted at the Kunming Institute of Botany, Chinese Academy of Sciences, the Kunming World Expo Park, and two households in Fumin County. Some suspect that wild individuals still exist, but they have yet to be found. If this continues, the tree could be declared extinct. But there's no need to despair; after all, those 11 trees still exist! There may still be a chance to save the Fumin Citrus, and some people are indeed working hard to save it.

image caption: The flowers of the Fumin trifoliate orange are pure and clean, with more stamens than the other trifoliate oranges. "

http://kbg.kib.cas.cn/kxjy/kpzs/kpwz/202209/t20220902_599371.html


In case picture in the above link becomes no longer available, I can attempt to describe it. The picture shows what appears to be an unripe or underripe large green fruit, appearing larger in size than a typical trifoliate orange, but appearing to have some sort of white fuzz, not looking so similar to the peel of a conventional citrus fruit, and further away from normal citrus than trifoliate orange fruits. The peel is bumpy and kind of gnarled, with a large folded indentation pushing into the navel side of the fruit.

The other picture shows a blossom, which looks significantly larger, thicker and fuller than a normal trifoliate orange blossom. The leaves appear in a similar configuration to trifoliate orange except the leaves look noticeably a little different, thicker and longer. I'd say definitely more like the leaves of standard trifoliate orange rather than than the "Flying Dragon" cultivar, but less stubby and more elongated than that.


In another picture (on another site, Kunming Institute of Botany) they show two fruits high up in a tree that appear to be more orange, but the fruits appear more in the distance and the picture of the fruits is obstructed by shadow due to the angle of the sunlight, so not the best clear picture. The fruits do look more bumpy and rough than most trifoliate orange fruits, and they definitely look on the bigger side compared to trifoliate orange as well.
http://english.kib.cas.cn/rh/rp/201301/t20130128_98591.html

In all these pictures, I also notice that the branches seem to have only very tiny thin stubby short spikes, and fewer of them, much more mild than trifoliate orange, and almost less spiky than a rose bush.