Citrus > Cold Hardy Citrus

Low protection Citrus experiment in zone 7b France

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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. :o 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.  ;D

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?

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