Low protection Citrus experiment in zone 7b France

[Rei]

Hello everybody ! I'm new on the forum, after years of reading posts I've finally decided to create an account and share my passion with you all ! Thanks eyeckr for helping me with getting my account approved !

I've been growing plants since my childhood, but only started seriously getting into gardening five years ago. While looking for fruit trees to grow, I discovered hardy citrus, and started experimenting with them in late 2020.
I live in North-Eastern France, and while this area used to be a clear zone 7a in cities, climate change has warmed the area somewhat and cities are now more like 7b-8a depending on their size and location. The specific place where I live got -18°C (0°F) in 2012, and since then we haven’t had anything below -14°C (7°F), and we’ve had a lot less big freezing events than we used to. Most years the minimum is around -12°C (10°F). We generally get frost from mid-november to mid-april, and big winter freezing events can keep temperatures below freezing day and night for up to three weeks.
Most of my citrus are grown away from the house, close to a west facing wall, but some are away from the wall and get more frost and wind. Everything I plant in ground is grafted to Poncirus, and I only protect my youngest and most sensitive plants during the coldest nights. Once they’re established, I let them deal with the cold on their own.

FALL 2020 (bought my first hardy citrus, quite disappointed) :

• Prague Chimera (thin and weak rootstock)
• Changsha Mandarin (grafted low on weak rootstock)
• Yuzu (grafted low on weak rootstock)
• "Sudachi" which I discovered later was actually a Hanayu (grafted low on weak rootstock)

FALL 2021 (bought more, from a different nursery this time, the rootstocks and plants were a lot better, aside from one) :

• Dunstan Citrumelo
• N°1 Tri-Voss (probably citrumelo x ichangensis rather than poncirus x ichangensis)
• Australian Desert Lime
• Eremorange (glauca x sinensis)
• IVIA-358 Ichang Papeda (very unhealthy, yellow with severe bark cracks)

SUMMER 2022
I planted all of my hardy citrus, despite not knowing which ones had any possibility of surviving at my place… It was quite a big mistake, in retrospect. But I couldn’t have known what was coming…

WINTER 2022-2023
After a surprisingly mild fall, the first winter frost came very late, about a week into december. At that time, I was out of the city and had to stay bedridden for weeks due to COVID-19. Worse yet, the first frost of the winter was also its worst ; the first freezing night got down to -13°C (8°F), and temperatures stayed below freezing for a week, with night temperatures ranging from -11°C (12°F) to -8°C (18°F) during these few days. When I was finally able to go home, all these citrus I would’ve liked to cover were dead, and there was heavy damage throughout my garden due to many plants not going dormant. :'( 

• Prague Chimera : defoliated, otherwise undamaged
• Changsha Mandarin : dead
• Yuzu : killed to just above graft, then woke up too early in spring and died from frost damage
• "False Sudachi" Hanayu : undamaged somehow, but didn't grow at all the following year
• Dunstan Citrumelo : very heavy trunk damage, I don't think it was dormant
• Australian Desert Lime : dead
• Eremorange : dead
• IVIA-358 Ichang Papeda : defoliated, but died at the graft in spring due to its already poor health
• N°1 Tri-Voss : undamaged

SUMMER 2023
The only citrus I added in ground in 2023 was a replacement Yuzu, selected for its cold hardiness. After these losses, I decided not to gamble with sensitive trees anymore, and to instead slowly plant more and more sensitive ones over time, as I get better at taking care of them and I figure out what exactly is the limit of what I can do with my methods.

• Prague Chimera : Low vigor, but some growth in spring
• "False Sudachi" Hanayu : Barely any growth in spring due to slugs targeting it
• N°1 Tri-Voss : Vigorous growth in spring, became a bit yellow in summer
• N°3 Yuzu : Decent growth in spring, suffered from heat in summer
• Dunstan Citrumelo : Grew a few leaves, then slugs girdled it and I failed a bridge graft

WINTER 2023-2024
After a moderately frosty but not especially cold early winter, we got hit by a cold wave in January 2024. Temperatures stayed below freezing for 19 days, with some rather cold nights, as low as -13°C (8°F) once again, yet I decided not to cover any of my citrus. And then, something unbelievable happened : starting from late january, there were no more frosts AT ALL. Temperatures were chilly, but never reached freezing levels again. Many of my plants that usually suffer from spring frosts were completely unaffected this year. Climate change really is crazy sometimes…

• N°3 Yuzu : Very light defoliation, otherwise undamaged
• "False Sudachi" Hanayu : Undamaged yet again
• Dunstan Citrumelo : Defoliated
• Prague Chimera : Mostly defoliated, aside from three leaves
• N°1 Tri-Voss : Undamaged

SUMMER 2024
I added plenty of new citrus in the garden, since they had done well in pots with some light protection in winter. I decided to get a new Prague Chimera since my older one was not doing anything with its very thin rootstock, I replaced my dead Ichang Papeda, and got a real Sudachi this time, along with a larger Hanayu. My two most sensitive plants were now this Sudachi and a Yuzandarin. Both can grow in zone 8a, and are related to Yuzu, so my thinking was that if they do well then I could probably succeed with ClemYuz and maybe attempt Changsha or Keraji. I also started to look more into Citrus breeding, to eventually make my own crosses. I now have a decent idea of what I’m going to attempt in a few years, once I start getting fruit on both my hardy and potted citrus.

• Morton Assel Citrange : Good growth, slightly yellowed in summer but quickly recovered
• Prague Chimera (old) : Ants ate all of its new growth for some reason. Great…
• Prague Chimera (new) : Good growth, branched out quite well and stayed green all summer
• Five Stars Citrumelo : Very vigorous, but was yellowed by the summer sun
• IVIA-358 Ichang Papeda : Good growth, but was yellowed by the summer sun
• Tokushima Yuzu : Good growth, slightly yellowed in summer but quickly recovered
• Hanayu : Good vigor, but was yellowed by the summer sun
• "False Sudachi" Hanayu : Medium vigor, it finally got some side shoots ; it’s now doing well
• N°3 Yuzu : Low vigor but healthy, probably because it wasn’t expecting that much winter cold
• Seneca Sudachi : Good vigor, but was yellowed by the summer sun
• N°30 Yuzandarin : Medium vigor, slightly yellowed and chlorotic but recovered somewhat
• N°1 Tri-Voss : It bloomed ! No fruits though, and barely any new growth.
• Yuzumelo (Yuzu x Citrumelo) : Good vigor, very healthy plant, stayed green all summer
• Dunstan Citrumelo : It grew one short stem with two green leaves. It refuses to die !

WINTER 2024-2025
As of January 23rd 2025, everything is doing well. Despite this winter being rather frosty, it hasn’t been that cold, with only a few nights between -6°C (21°F) and -8°C (17°F) and only one five day long freeze. Even my potted sweet citrus remained outside without protection, including my seedling Nagami kumquats which pot was frozen for a few days, although all of my potted plants are close to the house and get some protection from it.

• Morton Assel Citrange : Undamaged
• Prague Chimera (old) : Undamaged, kept the same three leaves from the previous winter
• Prague Chimera (new) : Defoliated, otherwise undamaged
• Five Stars Citrumelo : Undamaged
• IVIA-358 Ichang Papeda : Undamaged
• Tokushima Yuzu : Undamaged
• Hanayu : Undamaged
• "False Sudachi" Hanayu : Undamaged
• N°3 Yuzu : Undamaged
• Seneca Sudachi : Undamaged
• N°30 Yuzandarin : Very light defoliation. It’s the only in-ground citrus that suffered from cold.
• N°1 Tri-Voss : Undamaged
• Yuzumelo (Yuzu x Citrumelo) : Undamaged
• Dunstan Citrumelo : Undamaged

My plans for spring 2025 are to plant a HRS-899K citrandarin and a healthy Dunstan Citrumelo replacement. I’m not going to pull out the one I have, it’s still trying to live, even though it’s basically been a very badly damaged stick for years. I might add a few more trees, it depends on what I manage to get my hands on until planting season. I recently got a Kabosu, a Thomasville Citrangequat and a 11C Ichangquat, but I think they’re a bit too small to go in the ground yet. By the way, I’d be interested in getting some varieties from forum members, such as N°82 Citrumelo, Poncirus+, HRS-899A citrandarin, or Ichangquat 6-7-2. Some of Ilya’s selections also seem really interesting, and are very inspiring. I’m eager to start pollinating flowers !

Thanks a lot for reading ! I’ll post some pictures in a few days, as the weather warms up a bit and I dare go outside again. 

[Wahl]

Looks like you are doing some great stuff. It seems like your weather is a lot like mine.

[Skandiberg]

Hello Rei,

Welcome to the forum!

Thanks for the detailed report. I am especially interested in the development of your N30 and Tokushima yuzu.

From the weather details you shared, your climate is quite close to mine so if anything grows well there, it will be indicative for me, too. Good luck with your plants!

[Ilya11]

"By the way, I’d be interested in getting some varieties from forum members, such as N°82 Citrumelo, Poncirus+, HRS-899A citrandarin, or Ichangquat 6-7-2. Some of Ilya’s selections also seem really interesting, and are very inspiring."

Just ask me when ready to graft and welcome to the forum.

[Till]

Welcome to the Forum, Rei! And thank you for the detailed report. It seems that our climate is quite similar. I live near Aachen (Aix-la-Chapelle) but around 500m above sea level. Your winter seems similar but summer are probably warmer. How does pure Poncirus do in your climate?

[Rei]

Looks like you are doing some great stuff. It seems like your weather is a lot like mine.

Thank you ! It is similar yes, but I believe you get a lot more heat and a longer growing season in Alabama, if I'm not mistaken ? I've only started watching your YouTube channel recently, so I don't know enough to compare !

Thanks for the detailed report. I am especially interested in the development of your N30 and Tokushima yuzu.
From the weather details you shared, your climate is quite close to mine so if anything grows well there, it will be indicative for me, too. Good luck with your plants!

My pleasure. I'm going to post updates about their development in the future, but so far the Tokushima Yuzu has been a very good performer. It remains to be seen if it really is early ripening ; hopefully it will bloom in a year or two. N30 Yuzandarin isn't doing the best right now, but once it's established I'm hopeful it's going to do well.

Just ask me when ready to graft and welcome to the forum.

Thanks a lot for your support ! I brought in some potted Poncirus last week to try and do some early grafting, I'll make sure to contact you once ready. I'm still a beginner at grafting though, I don't have a great success rate yet.

Welcome to the Forum, Rei! And thank you for the detailed report. It seems that our climate is quite similar. I live near Aachen (Aix-la-Chapelle) but around 500m above sea level. Your winter seems similar but summer are probably warmer. How does pure Poncirus do in your climate?

Thanks ! I'm directly south of you, between Metz and the Luxemburgish border, at about 200m elevation. I never had any issues with pure Poncirus, in fact they do well even when neglected, although they don't grow as much. With full wind exposure I've never seen any damage on them. I only have a few years of experience with them though ! I have acquaintances at higher elevations close to where I live (400m), and for them Poncirus does get damaged. They have a lot more wind than I do and very harsh late frosts though (-8°C in april isn't uncommon for them).

[Mulberry0126]

Thank you for sharing all of this. One variety that caught my eye is Yuzumelo. If I am unable to obtain seed of this variety, I may attempt my own cross. Perhaps 5star x Yuzu. I hope you can get your hands on N°82, it looks like an exceptional citrumelo. The Iva Swingle citrumelo that we have in the US looks similar and tastes quite good.

[Rei]

I know some people have already had fruits from it, but I'm willing to send some to you once I get fruit in a few years, if you're still interested by then. I'm planning on using it to cross with sweet citrus (my main goal is to create various types of sweet citrus hardy to 7b). It's a really beautiful plant too, it would work well as an ornamental.

5Star x Yuzu seems promising for a hardy lemon, Ilya got some good results from this cross I believe.

Yeah, what I've read about N°82 is really encouraging, I don't know how hardy it is though. Hopefully it's similar to 5Star, it would be a great parent for further breeding if that's the case.

[Peep]

Thank you for sharing all of this. One variety that caught my eye is Yuzumelo. If I am unable to obtain seed of this variety, I may attempt my own cross. Perhaps 5star x Yuzu. I hope you can get your hands on N°82, it looks like an exceptional citrumelo. The Iva Swingle citrumelo that we have in the US looks similar and tastes quite good.

Here in Europe there is a Yuzumelo (Yuzu x Citrumelo) that has been around for quite some time, and availalble at a fair amount of nurseries. However the reports on it's fruit seem a bit sparse. It gets both negative and positive taste reviews. The hardiness hower always seems to get positive comments, so that's good.

The other interesting one is Staruzu (5Star x Yuzu) from Ilya, which some forum members seem to have grafted now and hopefully we get some reviews from different people soon.

Personally I expect that Ilya's hybrid might have better taste, but the hardiness is less proven at this time. I have both to compare, but my Yuzumelo has dropped it's flowers/fruits so far (also due to wet spring last year), and my Staruzu graft is still quite small (I will see if I'm able to cut a piece and regraft it on larger and more vigorous C4475 this year).

[mikkel]

Hello Rei, thank you for your report and welcome to the forum. You've already gained a lot of experience, that's great! haven't you been active in any forums yet?

Concerning the Yuzu Citrumelo discussion:
In my opinion, Staruzu is the better choice than Yuzmelo from Zdenek (which you can get from e.g. Adavo, for example)
Yuzmelo Zdenek is quite hardy, Staruzu should be similar, but there is hardly any experience yet. Yuzmelo has already survived frost while in pot, not very deep frost but sufficient. The leaves also turn slightly reddish in winter temperatures, as if hinting at autumn coloration. However, the coloration disappears completely in spring. There is no real leaf litter as with Poncirus.
I've had one fruit on Yuzmelo (Zdenek) that wasn't fully ripe and tasted distinctly of Poncirus hybrids, not good in my eyes, perhaps they are different when they are fully ripe.

These were my notes, (but it wasn`t fully ripe):

Initially, immediately after cutting, the taste is typical of Poncirushybrids, a coniferous aroma can be clearly tasted, but no bitterness. The fruit is simply sour with secondary aromas.
After half a day it only tastes sour and like unripe grapefruit.
Definitely not a fruit for eating raw.

Staruzu was a fruit that I found quite similar to a lemon, with a pleasant lemon scent, but no secondary aromas, not even resin, just a slight bitterness that didn't bother me. My children simply called it a lemon.

Staruzu , top center

[Till]

Ilya has just recently sent a fruit of Staruzu (5 Star x Yuzu) to me. It was as big as a big Clementine or small orange. It contained only a few seeds. Taste was sour and aromatic with a good proportion of bitterness, the kind of bitterness you know from grapefruits or Ichang Papeda. No internal oils. Very juicy. I am not a real friend of bitter fruits, yet I found it pretty good for lemonade or as a spice for cooking.

[Rei]

Here in Europe there is a Yuzumelo (Yuzu x Citrumelo) that has been around for quite some time, and availalble at a fair amount of nurseries. However the reports on it's fruit seem a bit sparse. It gets both negative and positive taste reviews. The hardiness hower always seems to get positive comments, so that's good.

That's the one I have. I got it from a small belgian nursery in 2023.

Hello Rei, thank you for your report and welcome to the forum. You've already gained a lot of experience, that's great! haven't you been active in any forums yet?

I've had one fruit on Yuzmelo (Zdenek) that wasn't fully ripe and tasted distinctly of Poncirus hybrids, not good in my eyes, perhaps they are different when they are fully ripe.

Thanks ! No, it's the first forum I joined, I was just reading posts before, never posting. I did leave comments on some members' YouTube videos though.
Thanks for sharing your experience with it! I was told it was quite good, juicy and without poncirus influence... I guess I was lied to, or maybe it depends on ripeness or growing conditions. At least it's not bitter, which is a plus. I'll definitely write about it once I get fruit. Staruzu seems quite good, I hope it's hardy too!

[Mulberry0126]

Great...looks like Staruzu is on my list now! Haha, it seemed like a good cross considering 5star's lemon-like flavors mixed with citrumelo. I don't mind a touch of bitterness, if it's free from strange resinous flavors that is most important.

[Wahl]

Sounds great. I wonder what the cold limit will be on it.

[Ilya11]

The lowest temperature it experienced was -11.5C, no damage at all.
It is now  around 4 m high, never protected.

[Florian]

Ilya kindly sent me Staruzu budwood in 2022 and my two plants have grown very well but they haven't flowered yet. I can't wait to taste the fruit.

[Rei]

Here are the pictures I promised:


N°1 Tri-Voss. It lost some leaves due to slugs, but it's very healthy. A bit covered in dry mint though. It's planted in a rather exposed spot, but the mint might help somewhat with wind for now. Once the tree is bigger, it won't have any protection.


This one is the N°30 Yuzandarin. The lower (older) leaves were discolored by frost and most have dropped. These were somewhat chlorotic when I got the tree, it got worse in spring then better in summer. The new growth is fine though. The newer leaves are a bit curled up, I don't know why, but they grew like that.


This is my youngest Prague Chimera. It dropped all its leaves, I'm not sure if it's because it's young or if this strain is fully deciduous.


This is the Yuzumelo Zdenek, its new growth is red but it doesn't seem to have much red visible at this time. It grew very densely and vigorously though, it was very small when I first got it. I planted it away from the wall, as it shouldn't need it for survival or fruit ripening, since it's hardier than yuzu. It doesn't get a lot of wind thankfully, as there's plenty of deciduous shrubs around to shelter it.


This one is my older Prague Chimera. When trying to get a good picture I moved some rosemary branches and saw it had a lot more leaves than I thought. It must have had some growth later during the growing season. As you can see it looks very green and mostly monofoliate ; I've only seen misshapen leaves on this strain, never bifoliate or trifoliate leaves. If only it was more vigorous...


Tokushima Yuzu, growing fast and branching well. If it has good hardiness and is really early fruiting (that's its selling point) then I'm going to use it for breeding for sure.


N°3 Yuzu. It looks greener in person than in the picture. It has a clear leader, its lower branches don't grow as much, even though I'd like them to.


This one's the Hanayu I planted last spring. It's not been enjoying the sun, but it's just not hardened enough to withstand it yet. If you're curious, the small shrub at the bottom of the picture is a Tasmanian Pepper. I'm trying to acclimate them as well, they seem to do okay with the cold, but I've lost several in summer as young plants seem very vulnerable to droughts.


This is the Hanayu that was sold to me as a Sudachi. It looks greener in person. I've never seen any cold damage on it, not even defoliation. Hopefully it'll stay that way.


This is the Seneca Sudachi I planted last spring. It's quite yellow due to the sun, and unfortunately doesn't grow very densely. Hopefully that'll change before there's another cold winter.


This one's the Morton Assel Citrange. It branched out nicely, it was just a stick when I planted it. I don't know what's different exactly compared to the regular Morton, when I asked the nursery they told me its flavor is similar to mango. I've never had the opportunity to try Morton, so we'll see. It has been yellowed by the sun, but has partly recovered since then.


This 5Star Citrumelo is very yellow, my watering system wasn't working as it should've last summer and it barely had any water. Still, it currently is my tallest citrus, and had very good vigor for such a young plant. It's fully exposed to the wind, so it may be deciduous some years, but I don't think it should be a problem for its survival.


This Dunstan Citrumelo is, as you can see, severely damaged. It used to look like the 5Star, with two main leaders and some side branches, but now it only has one leader, with several large dead spots, and it's been girdled below graft. It is a bit exposed to the wind, as there's just some deciduous shrubs close to it (a peach and an autumn olive). I think I'll plant my replacement Dunstan close to the wall, to help it a bit... It should help with fruit ripening too.


And finally, the IVIA-358 Ichang Papeda. It's very yellow too, it has been rather sensitive to the sun last summer. The greenest leaves are the ones in the shade, north of the tree. This one also is away from the wall, but not in a very exposed spot ; there's plenty of deciduous shrubs all around it.

[mikkel]

just a short note, my small citrus also suffered greatly from the slugs last year. I  then had very good success with nematodes to decimate the slugs. just 1 week later almost all the slugs had disappeared. I only found new slug offspring again in the fall. whether the effect lasts this year remains to be seen.

[Rei]

Great...looks like Staruzu is on my list now! Haha, it seemed like a good cross considering 5star's lemon-like flavors mixed with citrumelo. I don't mind a touch of bitterness, if it's free from strange resinous flavors that is most important.

It's on mine too! I'm also interested in Ichangstars (5Star x Ichang Papeda), as they should be very hardy, Ichangstar70 in particular seems to have rather nice fruits. Ilya also made a Staraji cross (5Star x Keraji), one of them has sweet fruits and is hardier than Keraji. Ilya also made 5Star x Morton hybrids. I'm not aware of everything he did, but it's really impressive. You should add some more to your list! 

Here's where I read about Ichangstar and Staraji :
https://tropicalfruitforum.com/index.php?topic=32108.0
https://tropicalfruitforum.com/index.php?topic=57270.0

just a short note, my small citrus also suffered greatly from the slugs last year. I  then had very good success with nematodes to decimate the slugs. just 1 week later almost all the slugs had disappeared. I only found new slug offspring again in the fall. whether the effect lasts this year remains to be seen.

Thanks, I'll look into it! I've been killing them by hand so far, their numbers have gotten down but they're not entirely gone.

[Skandiberg]

Rei,

Thank you for the photo report! It will be very useful to see how your plants grow through the years.

[Ilya11]

Rei,
Your plants are underfed and probably your soil is too alkaline.

[Rei]

Yes, my soil is alcaline. I'm adding a lot of compost every winter to improve it. That's the only fertilizer I've been using.
This spot used to be the garbage spot of the house's previous owners, the soil is a mix of clay and sand, and there's a lot of pieces of plastic, glass, and metal buried everywhere (I've done my best to remove them). But it's also one of the most sheltered spots of the garden. I'm doing what I can with it. Once established I don't see any discoloration on my trees, but the first two years are rough for them.

[a_Vivaldi]

Compost is a soil builder, not a fertilizer. Its NPK values are very low. It's good for making soil healthier, but for hungry plants like citrus, you'd need to apply crazy amounts of compost to give them the fertilizer they need to do their best.

[Zitrusgaertner]

Yes, my soil is alcaline. I'm adding a lot of compost every winter to improve it. That's the only fertilizer I've been using.
This spot used to be the garbage spot of the house's previous owners, the soil is a mix of clay and sand, and there's a lot of pieces of plastic, glass, and metal buried everywhere (I've done my best to remove them). But it's also one of the most sheltered spots of the garden. I'm doing what I can with it. Once established I don't see any discoloration on my trees, but the first two years are rough for them.

Ripe compost does not react sour. The only way to lower high PH is to mix your compost with powdered sulphur and let this mixture ripen for 3 or 4 Months.
If you try 7gS for 1l of compost  you will get a rather sour compost that you can use for lowering the PH of your soil. For a good start of the season use horse manure as fertilizer.

[poncirsguy]

I have a large non producing Fukushu kumquat low grafted to Flying dragon that I did some cold testing on outside.  I covered the pot as
 well as the first 12 inches of trunk with leaves.  My goal is to get a strong single growth trunk that might produce fruit.