Author Topic: new thoughts on breeding hardier citrus  (Read 8255 times)

Walt

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new thoughts on breeding hardier citrus
« on: November 04, 2021, 04:56:23 PM »
I've been thinking a lot about hardy citrus breeding for some years now.  But new information and experience is changing my mind about several thing the last few weeks,

Ponciris trifoliata is hardy enough for my area,  And it is the hardiest citrus relative I know of that is readily available.  It crosses easily enough with good citrus, and I've always thought breeding from such crosses was the way to go.  The ONLY way to go.  People have told me they want to select within the pure P. trifoliata, and I thought that was stupid.  There isn't enough variation to make that way successful, I thought.

But what is really the problem with P. trifoliata as a crop?  The nasty-smelling resinous flavor, of course.  But there is at least one mutant without that problem.  Ponciris+.  And P. trifoliata is mostly nucellular.  Again Ponciris+ is zygotic so that is at least less of a problem.  In addition, P. trifoliata, its F1 hybrids, and backcrosses to mandarins (mandarin x P. trifoliata) x mandarin, are too sour and lack sweetness.  Granted, I've only tasted one mandarin backcross, Clemtriclem.  It is (Clementine x P. trifoliata) x Clementine.  And Clementine is not the sweetest mandarin.  But I have not read of any improvement over Clemtriclem.  Another problem is the size of Ponciris fruit.  They are small.  But that is a minor problem compared to flavor.

But all this means, really, is that more sugar (higher brix) and less acid (higher pH) is the whole breeding problem.  Or at least most of it.  Precocity, short time from seed to bloom, would be valuable, as with a certain set of breeding stock, progress will be set by population size, ability to measure brix and acid, and the number of generations.  Keeping generation time short would be very valuable.

But to select within P. trifoliata seems a dead end.  There isn't much variation in brix or acidity to select from.  At least I haven't found information that would make me think otherwise.  So crosses with other citrus is the only way to get the needed genes.  Fortunately, such crosses have been made.  Kumin and I and others have acquired such hybrids.  US 1279, US 1281, US1282, Us 852, 5*, are useful as seed parents as well as pollen parents.  Other varieties might be used as pollen parents if desired.  Citrangequats can't be ruled out, though they wouldn't be my choice.  Bringing in Kishu Seedless as a pollen parent seems worthwhile, as it has a dominant gene for seedless, and is said to be exceptionally sweet.

New hybrids could be worthwhile.  Precocity might be brought in from Laaz's Fast Flowering Ponciris, Etrog, or Hong Kong kumquat.  None of these are of proven value, but I am checking them out.

Hybrids of various citrus with Ponciris+ could speed up getting rid of the  Ponciris flavor.  Though a generation or two of selection should get rid of it where Ponciris+ isn't available.

The amount of Ponciris in a breeding population should be determined by your climate zone.  Zone 8, maybe zone 7, 1/4 Ponciris could be enough.  This would speed up the breeding in those areas.  I plan to make such seeds available in a few years,  when my breeding stock is older.  Kumin, in zone 6, has had some success with 1/2 Ponciris in zone 6.  What he does in the future is up to him.  He has already done in one generation what I thought would take several generations, so I'm not the one to tell him what to do.

I'm also in zone 6, and will be working with 1/2 Ponciris.  But I will also make some crosses of those 1/2 Ponciris with pure Ponciris.  This will give me a big population that can be grown without protection.  This population will include seedless plants from the Kishu Seedless mandarin ancestor, fruits lacking Ponciris famous flavor, various levels of brix and acid, and fruit size.    Of course, I'll be working on the 1/2 Ponciris population, but I'll have to provide some protection to keep seedless and some other genes in the population in the early generations.


Breeding stock I now have on hand include:

Ponciris trifoliata
Ponciris+ which doesn't have the undesirable Ponciris flavor and does have zygotic seeds.
FFP, Laaz's Fast Flowering Ponciris, which doesn't pass on its fast flowering to its seedlings when crossed with other citrus..  But it may pass it on to its grandchildren.  If so, it would speed up generation time.
B and J.  Bigger and juicier P. trifoliata.  100 seeds from Kumin.
Many seeds from a wild population.  Sent by orangedays.  These trees give monozygotic seeds.  These are to broaden the genetic diversity of my breeding population.   

Mandarins
Kishu Seedless.  Very small, but very sweet and has a dominant gene for seedless.  It can only be used as a pollen parent.  Half of its seedlings will be seedless.
Changsha.  Good flavor, good size, more cold tolerant than most mandarins, zygotic seeds.

Citandarins
US 852  85% zygotic seeds
US 1279  More than 95% zygotic seeds
US 1281  More than 95% zygotic seeds
US 1282  More than 95% zygotic seeds
Bishop Citandarin  Seedling of US 852.  An improvement in flavor.


Citrange
010 Citrange  Survived 3 winters in Pennsylvania.  Zone 6  Fruit quality unknown.  % zygotic unknown.
058 Citrange  Survived 3 winters in Pennsylvania.  Zone 6  Fruit quality unknown.  % zygotic unknown.
067 Citrange  Survived 3 winters in Pennsylvania.  Zone 6   Fruit quality unknown. % zygotic unknown.
These 3 are seedlings from the same tree, C-35.  Mother tree was 15% zygotic.  These were all grown and selected by Kumin.  He has reported his work elsewhere on this forum.  Very impressive work.
« Last Edit: January 04, 2022, 05:13:43 PM by Walt »

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #1 on: November 04, 2021, 05:43:39 PM »
Kumin has been reporting on his citrus breeding.  Of about 3,000 zygotic F2 seedlings from C-35 citrange, he had 12 survive in good health for the past 3 winters in Pennsyvania, zone 6.  Others survived with serious damage.  But lets look closer at those that survived in good health. 

12 out of 3,000 is 1 in 250.  The odds of getting a given plant is the odds of a suitable pollen x the odds of getting a suitable egg cell.  We don't know the pollen parent of these seeds, but it seems likely they had been self pollinated.  I'll assume they were.  So 16 x 16 = 256.  256 is close enough to 250 for my use just now.

So C-35 citrange gametes have a 1 in 16 chance of giving hardy seedlings.  I expect plain P. trifoliata gives 100% potentially hardy gametes.  So if C-35 had been pollinated by P. trifoliata, 1 in 16 seedlings would hardy in Kumin's area.  I am also in zone 6, but sudden temperature changes and lack of snow cover here might mean less survival here.  But this is still good enough for what I'm saying.

So I'm thinking about crossing citandarins back to P. trifoliata and to mandarins.  I want to get the seedless gene from Kishu Seedless into my breeding.  There are a few ways to do this. 

One is to pollinate a citandarin with Kishu pollen.  But such seedlings couldn't be grown outside in my area, nor Kumin's, with any chance of survival.

Another way is to pollinate a zygotic P. trifoliata with Kishu pollen.  Then use Pollen from those seedlings in further crosses with other citandarins, citranges, etc.  This is a good way. but I don't know how soon this all could happen.

A third way would be to make the cross (citandarin x P. trifoliata) x (citandarin x Kishu).  The resulting seedlings would still be 50% mandarin and 50% P. trifolitata.  The advantage of this method would be that someone in zone 7 or 8 might be willing to grow out the citandarin x Kishu seedlings in hopes of getting hardier mandarin-like fruit.  It could happen.  How much improvement would be found remains to be seen.  This would save me limited greenhouse space.  And I could grow out the citandarin x P. trifoliata seedlings outside.  Again, this would save me greenhouse space.  And perhaps 1 out of 16 would survive.

Back to Kumin's citrange F2 plants that have done well through 3 winters. With such strict selection, I'm sure that they will produce more than 1 in 16 useful gametes.  Using their pollen on citadarins is a logical plan.   No one knows what fraction of such seedlings will survive, but it should be much better than 1 in 250.
« Last Edit: November 16, 2021, 03:30:13 PM by Walt »

kumin

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Re: new thoughts on breeding hardier citrus
« Reply #2 on: November 04, 2021, 06:11:58 PM »
Thanks for your roadmap and report, Walt. Just a few comments on the citrandarins and selections 010, 058, and 067. This Winter will allow me to compare 1279, 1281, and 1282 in regards to cold resistance. Initial appearances are that 1281 and 1279 may be more cold resistant than 1282. 1281 shows the greatest Poncirus influence on the foliage.

Segentrange 010 is more cold hardy than 058 and 067. 010 shows more Poncirus influence, 058 and 067 are the most Citrus-like of all the trial survivors.
« Last Edit: December 30, 2021, 04:26:39 AM by kumin »

nullroar

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Re: new thoughts on breeding hardier citrus
« Reply #3 on: November 05, 2021, 01:12:19 AM »
The advantage of this method would be that someone in zone 7 or 8 might be willing to grow out the citandarin x Kishu seedlings in hopes of getting hardier mandarin-like fruit.  It could happen. 

Oooh! Oooh! Me! Pick me!

I'm currently trialling pretty much every variety of citrus that's reputed to be cold-hardy. Anyone needs a clay-soil, zone 7(b) test out here in north alabama across a few separate microclimates I prepare, just let me know :D

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #4 on: November 05, 2021, 12:07:24 PM »
Thanks for the offer.  It will be at least a year, maybe more.  W

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #5 on: November 05, 2021, 04:43:54 PM »
So far I've written only about mandarin breeding.   But I've given thought about breeding other citrus too.

-I like having finger limes around.  They aren't the greatest, but those little balls of flavor are nice in some things.  I've read that when it is crossed with other citrus, the seedlings' fruit have the same little balls of flavor, but they taste like the other parent.  I doubt that's exactly true.  But I don't doubt that when crossed with various other citrus, you will get lots of variation in flavor, and some of them will be good.

It seems that all finger lime's seeds are zygotic.  Good.  A single cross with a P. trifoliata would likely extend its range greatly.  Not zone 6, but it would give it another zone or two.  If the P. trifoliata parent was Ponciris+, the F1 might give fruits with the little balls of flavor that taste like sour orange.  Already it would be liked by some people.  Tastes differ.

But beyond the F1, possibly a backcross to Ponciris+ would put some seedlings into zone 6.  And some of them might have those little round bursts of sour flavor, instead of the elongated shape common to most citrus.  Selection for less sour and higher brix would increase the number of people who would like it.  I've got to get on this.  This is the only hardy citrus breeding plan that could succeed in only 2 generations.  Of course if anyone else wants to get on it, do it.  Its not that I have lots of time and space and nothing else to do.  And it would take some extra generations to get the gene for seedless into it.  But one could use the seeded ones until seedless ones are developed.


-Kumquats are one of my favorite citrus.  Like finger limes, they are all zygotic.  Unlike finger limes, I doubt many would like the F1 kumquat x P. trifoliata no matter which P. trifoliata is used.  Big populations and several generations might be needed.  Still it can be done.  Unlike the other citrus I've written about, the flavor and texture of the peel matters.  Well, the zest of the other citrus is used, but it is less important to many people.



-For grapefruit, 5* is one of the most used P. trifoliata hybrids.  A good start.  A cross back to grapefruit or pummelo would give a population that would include some that are good grapefruit.  Getting them into zone 7 or 6 would be several more generations.  And part of the problem is that grapefruit need a long season.  Zones 6 and 7 don't have long seasons. 


-Lemons and limes I'll lump together.  Neither have zygotic seeds.  None of them as far as I know have zygotic seeds.  So pollinate Ponciris+ with pollen from lemons (or limes, which can be treated the same way.  But I'll just say lemons to save time and space.) whichever you want to work with.  The fruits from F1 plants won't taste like lemons.  It will be sour, but the lemon flavor won't stand out.    Sure, the genes for the complex flaveres in lemons will be jumbled with the orange flavors on P. trifoliata.  So how to sort them out.  Sure, one could select based on subjective taste.  But I wouldn't be able to make out which is a liitle more lemony and a little less orangy.  So one possibility is to use s gas chromatology machine and find out what seperates the lemon flavor from the orange flavor.  Run a sample of orange juice and a sample of lemon juice.  Record the blips on the graph or screen for each.  Then run a sample of juice from each seedling.  Select those seedlings with the most lemon pattern.  So gas chromotology machines aren't cheap.  But I knew a professor  at Emporia State U. that built his own because he wanted to be able to carry it to the field to run really fresh root samples.  It can be done.  Or one could find a lab that would do it for you.  That could be very expensive.  Or you might find someone who would do it to get a good publication with their name on it.  That happens.  Infra red spectrscopy might also work.  Those machines have been home built.  It's been over 30 years since I've known of a homebuilt one, but it would't be any harder now.

nullroar

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Re: new thoughts on breeding hardier citrus
« Reply #6 on: November 05, 2021, 05:44:38 PM »
I keep seeing mention of “poncirus+” - what is this? I’ve got a gazillion standard poncirus, as well as lucky enough to have been able to get an early fruiting poncirus from Laaz. But I’m clueless about poncirus+.

My home is *filled* with finger limes in pots (red and green), so if there’s a potential way to extend their range and actually get them outside here in 7b, I’d love to hear it.

kumin

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Re: new thoughts on breeding hardier citrus
« Reply #7 on: November 05, 2021, 06:50:13 PM »
Ilya may have a clearer history of Poncirus+, but my understanding is that it was selected in Eastern Europe, perhaps Ukraine. There appears to be a little uncertainty as to whether it's fully as hardy as common Poncirus. Local Winters haven't been super cold during the past 2 years, so no real challenges in that respect. My trees are too young to have fruited so I have no personal experience with fruit characteristics.

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #8 on: November 05, 2021, 09:01:15 PM »
Ponciris+ iseported to lack the acrid flavor of other ponciris and to have at least some zygotic seeds.

nullroar

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Re: new thoughts on breeding hardier citrus
« Reply #9 on: November 05, 2021, 11:12:11 PM »
So a poncirus that doesn’t taste terrible? Or just tastes less-terrible? Is there a source for this? I’d love to compare to the normal poncirus and precocious poncirus I have.

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #10 on: November 06, 2021, 12:26:41 AM »
I have found that P.t and all of its hybrids and backcrosses to citrus I've tasted are very sour.    I expect P+ is also sour.  But add water and sweetener and they have all tasted OK.  Not really great, but OK.  I have only tasted regular P.t, a citandarin, a citandarin x mandarin, and and a Taiwan lemon x Pt
« Last Edit: November 16, 2021, 03:35:57 PM by Walt »

mikkel

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Re: new thoughts on breeding hardier citrus
« Reply #11 on: November 07, 2021, 02:50:29 AM »
Have you ever thought of Ichang Papeda? Is it suitable for your climate zone?
Ichang Papeda grows much better than Poncirus and some flower after 3 years, but not all.
Poncirus grows so unspeakably slowly that I am already wondering whether it is at all suitable for my climate.


This autumn I also got a (mostly) seedless Ichang Papeda. When pollinated, it sometimes does make seeds.



mikkel

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Re: new thoughts on breeding hardier citrus
« Reply #12 on: November 07, 2021, 02:58:43 AM »
I also thought about creating a hybrid swarm first, consisting of many different early bloomers.
As I understand it, early flowering in hybrids is often not heritable, probably it is a form of recessivity of one or more genes. So that the trait is quickly lost in the next generations.
Backcrossing could help, but that poses other practical problems, or perhaps a hybrid swarm of early-flowering varieties. Maybe different genes that produce early flowering can be combined with each other (provided it is not the same genes in all early flowering varieties) or, if it is the same genes, one can breed for better fruit quality within this swarm.
Later, an early bloomer with better fruit quality could be used for crossing with "normal" citrus.

Perplexed

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Re: new thoughts on breeding hardier citrus
« Reply #13 on: November 07, 2021, 12:17:00 PM »
Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #14 on: November 07, 2021, 03:57:45 PM »
Ichang Papeda isn't hardy enough for my location.  I thought about using both it and Pt.  But that would dilute the percentage of mandarin genes in my population.  That's a judgement call that others might disagree with.  But I take my best guess and go with it.

I wonder what a hybrid swarm from Ichang Papeda x Pt would be like.  But I must limit my efforts if I am to get anything done.

I do like it when other people give comments, offer additional ideas.  Its not like I know all about this.  I just make my best guesses and act on them.  And as I said before, Kumin showed that I was wrong about how quickly one can get hardier citrus.  Others may show that I could have gotten better or quicker results going a different way.  Good.  As long as there is progress, I'm happy.

kumin

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Re: new thoughts on breeding hardier citrus
« Reply #15 on: November 07, 2021, 05:06:02 PM »
I'm in agreement, Walt. Poncirus being the hardiest known Citrus relative and being hardy in zone 6, except in extreme Winters, all of it's hardiness is required for a reasonable chance at success. The first hardy hybrid selections will likely have their hardiness challenged during severe Winters. Deciduousness, true dormancy, and actual Winter bud scales are all important attributes that contribute to Winter survival. It's almost a requisite to conserve these traits in any new cultivars for zone 6.

There are obviously a number of hurdles to overcome, such as early ripening to beat Autumn freezes. There's a sense of needing all of the tree traits Poncirus brings to the table, plus all of the fruit traits Citrus brings to the table. A tall order, but also a great challenge!

SoCal2warm

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Re: new thoughts on breeding hardier citrus
« Reply #16 on: November 07, 2021, 06:36:33 PM »
Ichang Papeda isn't hardy enough for my location.
My information tells me it is only hardy down to zone 8a, or possibly even 7b in parts of the deep South (in the US).
I am growing two Ichang papeda plants in the Pacific Northwest, zone 8a, and they do not seem to be doing too well, although they appear to be surviving, in contrast to several Yuzu plants that seem to be doing well. This despite every source I've ever come across saying that Ichang papeda should be able to survive significantly more cold than Yuzu. My Ichang papeda plants have leaves that do not develop a dark green color, and I think it is because they do not like the cool to cold temperatures when they first begin leafing out in the late Spring. I have considered the possibility that the strain of Ichang papeda I have may not be the same variety that exists in other parts of the country, so I can not necessarily be certain of extending my observations to the Ichang papeda species in general. Maybe they just do not like the cooler weather and shorter growing season in this climate. But the Ichang papeda plants in Europe seem to be growing quite well, so maybe this is not true.

On the other hand, Ichang papeda doesn't have any of the awful flavor of poncirus, and I could even manage to eat the entire fruits, with the peel and all (though of course not the seeds). It seemed to be sour, not fully ripe, low flesh ratio, not much juice, flavor like citron or lemon with some lime, specifically kaffir lime flavor, but also a little reminiscent of Yuzu in a strange sort of way with some deepness, but not that little bit of spiciness that Yuzu has. Not really the best fruit quality but definitely edible. It reminded me very much of a citron, with its softer semi-edible peel and yellow lemon flavor. By comparison, Yuzu has a much more fragrant orange or mandarin orange like flavor.

I'd say that compared to Yuzu, Ichang papeda has a little bit of an overall inferior flavor and fruit quality, but the peel of a fresh Ichang papeda is also very slightly softer and more tender than a fresh Yuzu, although if you eat too much of the peel it can have a little bit of a skunky after-flavor.

It seems to me very few people have ever got the opportunity to actually taste Ichang papeda, so I hope these insights are valuable to some of you.
« Last Edit: November 07, 2021, 06:53:20 PM by SoCal2warm »

mikkel

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Re: new thoughts on breeding hardier citrus
« Reply #17 on: November 09, 2021, 10:24:02 AM »
Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.

I wouldn`t care. as long as these are vigorous plants and still quite cold hardy.

Perplexed

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Re: new thoughts on breeding hardier citrus
« Reply #18 on: November 09, 2021, 10:33:56 AM »
Ichang Papeda is not as readily available in the US as in europe. And most of the time when it is offered it is a hybrid seedling so it has other ancestry other than ichang papeda.

I wouldn`t care. as long as these are vigorous plants and still quite cold hardy.
Yeah they'll be vigorous till you get the seeds and found out that it has lemon as the pollen donor... how hardy is that?

mikkel

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Re: new thoughts on breeding hardier citrus
« Reply #19 on: November 09, 2021, 11:18:15 AM »
I don't understand what you're trying to say?
I didn't mean anything by my last post.
Of course, it doesn't make sense to cross Ichang Papeda with something that is sensitive to cold. One of my goals is to cross with Ichang Papeda to transfer vigorousity to hybrids.
Hybrids of "F1 Poncirus hybrids" with Ichang Papeda grow much better than pure Poncirush hybrids for me. But that is just my observation and only refers to my climate. It may not be helpful elsewhere....

Walt

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Re: new thoughts on breeding hardier citrus
« Reply #20 on: November 09, 2021, 11:28:46 AM »
"Hybrids of "F1 Poncirus hybrids" with Ichang Papeda grow much better than pure Poncirush hybrids for me. But that is just my observation and only refers to my climate. It may not be helpful elsewhere...."

I'll have to check this out.  Hybrid vigor can be a very useful tool.
I now have P. trifoliata from 5 sources.  I'll be comparing them for vigor, winter dieback, brix, acidity, and every other trait I can think of.  An important part of plant breeding is exploring your options.

Perplexed

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Re: new thoughts on breeding hardier citrus
« Reply #21 on: November 09, 2021, 03:13:48 PM »
Yeah you're right mikkel, ichang papeda hybrids are vigorous. One of my N1Tri/Ichangstar F2 grew about a foot since planting them in February of this year.

Perplexed

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Re: new thoughts on breeding hardier citrus
« Reply #22 on: November 09, 2021, 03:14:59 PM »
Only problem is finding an pure ichang papeda to be the female parent...

SoCal2warm

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Re: new thoughts on breeding hardier citrus
« Reply #23 on: November 09, 2021, 11:16:36 PM »
Only problem is finding an pure ichang papeda to be the female parent...
There's a very big bush-tree in the Hoyt Arboretum in Portland, OR, right up against the side of the visitor center.
I can tell you it grows very easily from cuttings.

For those in SC, Woodlanders sometimes has some, although they're prohibited from selling to you if you're in GA.

Keraji seems pretty promising too. Maybe you could try using Keraji to pollinate a zygotic selection of poncirus hybrid and hope for the best.
Loch Laurel sells Keraji but they do not do mail order.
« Last Edit: November 09, 2021, 11:24:47 PM by SoCal2warm »

Perplexed

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Re: new thoughts on breeding hardier citrus
« Reply #24 on: November 09, 2021, 11:49:20 PM »
Woodlanders ichang papeda is seed-grown, would be a gamble but I guess that's a way.