Author Topic: Citrus Cold Hardiness Questions - new forum member  (Read 468 times)

Falcon1547

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Citrus Cold Hardiness Questions - new forum member
« on: March 17, 2022, 08:43:35 PM »
Hello, just joined!

I live on the west coast of British Columbia, Canada. Technically zone 9, but I'll get into that in a sec. I've been growing mostly from seed, as I enjoy it, but also have a meyer and a sudachi. Living where I do, cold tolerance is a concern, especially because there is a high likelihood I will be moving to a zone 7 location in a few years.

In past winters, all my trees and seedlings have come inside in the winter, but I've gradually started leaving them outside longer...and then this winter decided to test them entirely outside. Of course this winter we had the coldest temperatures I have ever experienced in this location. It went down to -12 Celsius (10F), possibly a bit colder. In preparation for this, I moved my trees into an unheated garage and shed. They still definitely all experienced at least -5 (23F), the shed probably went colder. The most extreme was a Eureka lemon seedling and a rooted cutting, which were left wrapped outside the first night of the cold snap where it wasn't supposed to go below -5 (which I know it can take from experience), yet I woke up to -9. Presumably it was colder overnight. The pots were frozen completely solid. Fortunately, despite losing every leaf on the original tree, and all but 2 leaves on the rooted cutting, along with most of their branches, 2.5 months later both are putting on new growth. I lost a few seedlings, which I expected. The worst was a well-established potted meyer lemon which now has severe bark splitting. I sort of expect it to slowly die at this point. Compared to my seedlings it has always struggled. Do not know why.

What I am wondering is:

1. How do daytime highs impact citrus hardiness? A lot of zones are rated higher around here than most people think, partly because this is Canada, and partly because we tend to spend more time near the low end of our zones in the winter. Specifically I am looking ahead to my likely future, and wondering if poncirus is viable outdoors where it will experience cold snaps where temperatures do not come above freezing for days at a time.

2. My seed grown trees have been very impressive with their vigor, and now ability to withstand cold. What I am concerned about is their natural roots. Should I be acquiring poncirus for rootstock and grafting? Or are they likely ok if healthy so far? Does rootstock have any impact on cold tolerance?

3. My first store bought tree was the meyer lemon previously mentioned, and at the time I understood them to be hardy. Yet this plant has constantly struggled. No net growth over four years, constantly losing leaves, and now the bark splitting. Are there any reasons why this tree would struggle more so than others I have that are supposed to be less hardy?

Thanks in advance for any information that may help me better understand how citrus handle cold. Most of my learning so far has been my own from experience. Very little information about growing in this location.

I've included a pre-disaster photo of my "Shrimp-Ring Lemon". It is the Eureka lemon seedling I spoke about above. I call it that because I saved a single seed from a lemon wedge in a shrimp ring while preparing a batch of grapefruit seeds. It was an afterthought "why not" at the time, but is now one of my favorites, and fastest growing citrus trees. And apparently it can survive a pretty severe freeze.



kumin

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Re: Citrus Cold Hardiness Questions - new forum member
« Reply #1 on: March 18, 2022, 06:16:57 AM »
You have the advantage of the proximity to the Pacific Ocean giving you mild Winters. The disadvantage is the lack of heat during Summer. Hot Summers help mature and harden tissues, which in turn can better withstand cold temperatures, provided there's a period of gradual cooling.

Meyer lemon's cold hardiness is relative to subtropical Citrus, certainly not Poncirus. A Meyer lemon seedling in my cold frame got severely beat up, while Poncirus hybrids were unaffected. At -6C (21F)Meyer showed severe damage.
In regards to Poncirus hardiness, the fruiting buds of Poncirus often set full crops, during the same Winters that peaches fail to do so. Peach and Poncirus hardiness does differ, however. -30C is considered lethal to exposed Poncirus  branches. I find Poncirus hardier than Asian persimmons, less hardy than American persimmons. Zone 7 Winters should not be lethal to dormant Poncirus.

Poncirus hybrids are variable, with the hardiest selections beginning to approach Poncirus hardiness, although generally less palatable, even inedible.


Comparison of Meyer lemon seedling cold resistance and 5* Citrumelo cold resistance in a poly covered cold frame. Cold frame low temperature was -6C(21F).

Outdoor 5* Citrumelo withstood -15C  (5F).

A deciduous Poncirus hybrid (Conestoga segentrange #128)unaffected by repeated low temperature exposures of -15C (5F).


1. Daytime highs do factor into Citrus hardiness and survival. In one sense all subfreezing temperatures are stressful to Citrus. An additional issue is excessive daytime temperatures can lessen dormancy and cold hardiness.

2. Grafting unto Poncirus rootstock will deepen dormancy, as well as increase cold hardiness by a few degrees.

3 Regarding lack of Meyer hardiness, state of dormancy, any exposure to sun(or heat vents) while frozen could affect survival. Meyer is not really tolerant of frozen tissue for an extended period.

« Last Edit: March 19, 2022, 06:06:22 AM by kumin »

Falcon1547

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Re: Citrus Cold Hardiness Questions - new forum member
« Reply #2 on: March 18, 2022, 01:44:50 PM »
Thanks so much for the reply kumin. That is extremely helpful. The ocean is indeed why it is so mild here. The only exception is the extreme weather that pulls arctic air down - something that has gotten worse in the past few years. Warmer on average with the occasional temperature dive.

That makes sense in regard to meyer hardiness, but I am still a little confused why seed grown trees from grapefruit, eureka lemon, and a variety of oranges are less bothered. Unless I either got lucky or living their whole lives here helped somehow.

The explanation of daytime temperatures makes sense, but is the opposite of what I've heard said elsewhere. I'll definitely be watching out for warm spells from now on before a freeze.

Just need to figure out where I can get some poncirus and hybrids in Canada. Most places only carry Calamondin, Meyer, and some type of lime.

kumin

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Re: Citrus Cold Hardiness Questions - new forum member
« Reply #3 on: March 22, 2022, 07:16:39 AM »
One potential source of Poncirus hybrids is the rootstock used for conventional Citrus, provided the labelling is accurate. Most of these would rank rather low on the palatability scale. Cultivars such as Thomasville should be better in regards to palatability, provided they can withstand your Winters. Most Citrus benefits from hotter Summers, Poncirus appears to be slow growing in central Europe despite being Winter hardy. Having a open ended (during Summer)  poly tunnel on the East Coast has allowed 2 of 5 Poncirus+ seedlings to flower at 3 years of age. In an outdoor setting it normally takes 5-6 years.
« Last Edit: March 22, 2022, 07:18:42 AM by kumin »

Falcon1547

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Re: Citrus Cold Hardiness Questions - new forum member
« Reply #4 on: March 23, 2022, 02:24:46 PM »
Thanks, I think I will try and source a variety, but flying dragon may be the best I can do.

 

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