All Things Cold Hardy Citrus, news, thoughts and evaluations


#1

I know that there have been other threads about cold hardy citrus, but I decided to introduce this one with a more generic title so that it becomes a catch all for information about cold hardy citrus.

Above is a photo of my Lemon Frost lemon which of my citrus is doing the best so far. It has survived one winter here in SE Georgia with the help of Christmas lights. I cover my citrus trees in small incandescent Christmas lights, and so far here in Hardiness Zone 8B at least that seems to be enough with a painters tarp over the trees on cold nights.

Here are my thoughts on Lemon Frost so far. It’s about 1/4th lemon, 1/4th orange and 1/2 hardy tangerine. This year the lemons have generally had one or two seeds. They are tart but kind of sweet too. As they ripen they go from green to yellow to kind of gold / orange and to me look more like an orange than a lemon. They peel like a satsuma or tangerine. When they are orange ripe, they really are kind of sweet, sweeter than the Meyers lemons I’ve tried.

With the new government regulations on propagating and distributing citrus, the company that owns the rights to all the Texas A & M Frost Series Citrus has decided to get out of the citrus business, so this variety probably won’t be available for a while. The nursery where I got my Lemon Frost has heard a rumor that the rights to the Texas A & M Frost Series varieties have been bought by another nursery. I don’t have any information on this matter beyond that, and I don’t know when nursery stock of this variety will be available again commercially if ever. Thanks and God bless.


#2

Is this plastic or canvas?


#3

The canvas one goes over Lemon Frost because that’s the most frost tender variety. I have a new very light weight one made out of some fiberglass like material which will go over the most exposed Arctic Frost Satsuma. With lights this should be enough. The plastic tarp will go over the less exposed Arctic Frost which may or may not get lights depending on weather predictions. (Arctic Frost is supposedly cold tolerant to about 12 degrees, but I don’t trust that. At least I won’t until the trees get bigger, and I have more experience with them.) Orang Frost is fairly small and has some tender growth on it still, so it will get lights and probably an old bed sheet or something similar and some plastic over that even though it’s in a fairly protected spot. Owari and Browns Select both really hug the house, and neither have tender growth, so they will only get old bed sheets unless we get predictions of temps in the low 20s. Trees that don’t get lights also get a five gallon bucket full of water sitting next to the trunk. Water will not go below 32F unless it’s completely frozen, so a five gallon bucket can be effective at protecting the graft and the trunk below it. I pile up leaves over the root systems of the trees during winter. But they need to be raked away in spring.


#4

I will make this observation on the Texas A & M Frost Series trees. The nursery that distributed them propagated them as rooted cuttings. That means they are on their own roots. The nursery’s claim was they did that rather than grafting the trees onto C. trifoliate root stock, so that if the trunk was ever killed by cold, the trees could come back from stump growth. This is what I’m observing.

These “Frost” citrus are much more aggressive growers than the varieties on trifoliate rootstock. Arctic Frost is only supposed to be about 10’ tall at maturity. Both of my Arctic Frost trees just finished their second growing season. The more exposed one got yacked back a lot by frost in last Spring’s late freeze which hit right after it had put out a bunch of new growth. Even so both trees are now about 8’ tall. They better be cold tolerant because by next year they will be too big to protect if they grow like they did this past season. I don’t believe for a minute that Arctic Frost is going to want to be a ten foot tall tree given its fast growth.

Depending on how they do this winter, and if they act like they will require more protection that I can pull off once they reach mature size, I might try grafting them onto some C. trifoliate root stock to make sure that I have some slower growing trees that don’t get so big to replace these with. God bless.


#5

What is the parentage of this lemon frost?

I know arctic frost, bumper, orange frost are changsha vs satsuma hybrids.

I’ve never seen the history of this lemon frost plant though. Sounds like maybe meyer x changsha?


#6

It’s Meyer X Hardy Tangerine. I think Hardy Tangerine has Changsha in its genetics, but I’m not sure on that. Lemon Frost does not have as noticeable Changsha aftertaste as Arctic Frost. Lemon Frost has about the same level of cold tolerance as Meyer Lemon as best as I can tell from the literature. It’s sweeter than Meyer when orange ripe.


#7

I have 2 of the 3 new uga citrus varieties. We’ll see what they do next year. My citrangequats continue to truck along, producing every year with no issues other than insect damage.


#8

Do you have issues with the long thorns destroying your tarp?


#9

No. The long thorns have been mostly restricted to the vigorously growing main branches not the smaller branches where the fruit is formed. At least that’s been the case so far. The smaller thorns on the branches are still prickly though. This might make picking fruit in high branches a pain with Arctic Frost both figuratively and physically.


#10

I’ve been talking with the provider and hope to get a Pink Frost grapefruit and a Sweet Frost Tangerine this spring. The only thing is, I need to figure out a space for a 25 ft diameter tree which is what the nursery indicates Pink Frost will require. That’s a pretty big tree by fruit tree standards. Once again. Something that big has to be cold resistant to survive in my yard. There is no way that I can afford to cover a tree that big. God bless.

Marcus


#11

I’ve been thinking about this recently. I have a bunch of questions I’ve never gotten a straight answer to. I’m in a similar situation and have done much of what your doing, although I have no electricity.
Where I’m located, there is an impressive variety of grafted citrus trees available. But it’s difficult to know which ones will bear fruit to maturity outdoors in my zone.
For example, If I understand correctly, there are early, mid, and late bearing mandarins that range from September to January for harvest. This is not including the many hybrids available, some of which claim to ripen outside at this time.
We get frost starting around oct/nov. I just had my first big Mandarin harvest off of one of my trees (unknown variety), all ripened up by early nov, so no worries.
What of the citrus that ripens later?
Is there critical point where it must reach before the temperature drops to a certain level?
Do different citrus follow different rules in this regard?
Am I limited to citrus that lists a harvest time before November?
There doesn’t seem to be a clear guide in this regard. For example, my kumquat tree, while by far the hardyest and recommended for cold, never ripens most of the fruit due to cold. While my shikwasa , A subtropical, is reliably giving me my best harvests, every year in sept/October, and is able to pull through the winter with manageable damage.
Also some which are supposed to be ever bearing, such as my Eureka lemon, only seem to put out flowers in September.

On a related note, it’s common to harvest some of my citrus varieties while they are still green (kabose, sudachi, shikwasa, yuzu, etc). This makes it easier to harvest them before the winter, and some taste great as a lemon/lime like sour juice. but I’m wondering when this is a bad idea. For example, I tried this with some Mikan mandarins, and they tasted too acidic and harsh.
What exactly are the qualities of citrus, and what affects them? Sour and sweet doesn’t seem to cover all of the aspects.


#12

You are growing a lot more citrus and more different types than I am, and it sounds like you have been at it longer than me. My basic understanding is that 26 F is the temperature where fruit gets damaged for most varieties. It hasn’t gotten that cold here in Statesboro, Georgia before Christmas in a long time. My guess is that ripening time will be the big issue with Pink Frost Grapefruit since Grapefruits tend to ripen fruit all through the winter. I imagine I will loose some fruit some winters. But maybe Christmas lights even without a tarp over a big tree will help preserve the fruit that more inside the tree. I for one am learning as I go. For the UGA and Texas A & M Frost varieties we are all learning together.


#13

My Browns Select satsuma seems to be every bit if not hardier than my Arctic Frost. I think the only reason they list AF as hardy to 10 degrees is because it is on its own roots, meaning the roots will survive at 10 degrees.


#14

I’d love to see a picture of the whole tree!


#15

It is very subjective., Citrus are chemical factories with so many flavors that originate from particular lineages. The flavor of a fruit could differ because fruit A has α-Pinene and fruit B has (neg)α-Pinene . (neg)α-Pinene is common in European Pine and (pos)α-Pinene is common America Pine. That difference in flavor might make one fruit more appealing to one market then another. α-Pinene is also present in rosemary which might explain why lemon and rosemary pare well togather. β-pinene is common in hops and cannabis, coriander is rich in α-Pinene. the combination could explain why summer wheat beers which are seasoned with coriander and citrus peal paired with Orange and taste so good. But what if you used Kaffir lime which is rich in β-pinene, could be great could be terrible, I dont know just theories.

To continue with my brewing analogy, you do not brew with juice. I would want a Citrus with my favorite flavor component concentrated in the peel or leaf. So that means you want citron heritage crossed with something else. Say I am going for that β-pinene that means crossing Citron (Citrus Medica) with Citrus Papeda (kaffir,kabose, sudachi, shikwasa, yuzu) and hoping you find a hybrid that produces β-pinene not α-Pinene and also does not produce neoeriocitrin the primary flavor in bergamot ie Earl Gray Tea. Finally when my beer is served you want it to be with the citrus juice that complements it. So that means when you brew you want less of the flavor components that are common in retail lemons and limes so when combined it enhances your product. There has to be at least 2 dozen major and many more minor flavor components and other chemical in citrus that create the all the complex tastes.

ps: the pepeda citrus you mention just there juice as they ripen so you have to pick them “green” in to get any juice.

Commercially whats important ripening time, storage hardiness, percentage of juice, easy to peel.

so at the end of the day what makes a good citrus is either what you like, what you can sell or what you can grow.


#16

The only citrus in my yard that got hurt bad by the late frost was Arctic Frost. Brown’s Select sailed through without any damage at all.


#17


The photo above is of my Lemon Frost which I just covered in incandescent Christmas lights which I got from our Local Habitat for Humanity ReStore. They were $1:00 a string. You can’t beat the price! Yes the white string is tacky on the green tree. But it’s functional. LOL! I also need to tidy up my yard soon.

I now have a new appreciation for just how thorny these Texas A & M Frost Series citrus are after this exercise of putting Christmas lights on them.


The citrus tree that I kind of worry about the most for this upcoming freeze event is the small Orange Frost satsuma above. It’s small but most worrisome is that it still has lots of tender growth on it from a recent flush. Hopefully the lights and a covering will do the trick to protect it. My big hope is that cold snap will convince it to hurry up and harden off before we get some temps in the low 20s. At last peak at the weather forecast, the coldest it’s supposed to get this weekend is around 30F. That really should not bother any of my citrus except this one with the young growth even if I did not provide protection. God bless.


#18

I’m not sure I’m actually a 9B. I’m sure drops below those temperatures you’re mentioning. I know other factors affect situation, and that’s where I get very foggy on this. I read quite a bit on this, but there still critical info gaps about what I can and cannot grow. I don’t want to be several years into a tree just to find out it misses some critical mass point, and I’ll never get edible fruit off it.
I’m sure for each tree the fruit must reach a certain stage before it drops to certain temperature, or you’re never going to get fruit. To make it more complicated though, I’ve heard it’s common for Mandarin here to ripen in the snow, Or after you’ve picked it, to leave it and it will sweeten on the shelf. I have a hard time believing the quality of even ripe fruit on the tree would be unaffected below a certain temperature for a certain amount of time. I’m guessing you would get some kind of damage or drying out of the pulp etc.


#19

That’s interesting information, but I’m primarily interested in the main factors. I’m guessing for most citrus there is a critical point for ripening, where triggers a change in the sugars. Kind of like how KIwai convert starch into sugar. If you go before that you’re never going to get fruit.

Through experience, I figured out I’m safe if the fruit ripens by October. However I’m trying to extend the season, and wondering how I can do that other than growing a variety of trees for a few years.
As I mentioned, Locally I’ve only seen Mandarin and Yuzu grown. However, I successfully grow Sudachi, kabos, and shikwasa in ground, so I know there are other possibilities that people don’t grow here.
I also wasted a lot of time and effort on varieties it’s obvious are never going to produce well for me here, like navel oranges or lemons.
There are a huge variety of hybrids available locally, and it’s impossible for me to plant them all. It would help to have some general guidelines like I’ve mentioned above so I can find out my best options.


#20

If you are in Zone 9 at all, you have more rope than I do in Zone 8. For some of these things you may have to experiment unless you can find local people growing or who have attempted to grow what you want to grow. People have successfully grown grapefruit in the Statesboro area, so that’s why I’m trying it. My guess is that the fruit ripens late enough in winter that I won’t get a great crop every year. I’m not attempting a commercial operation and don’t need hundreds of pounds of citrus every year, and we miss twenty six degrees often enough that lowquats are worth growing for some people. What I can say is that the little bit of fresh citrus I’ve gotten so far has been better than what I can buy.

As for comquates I have one year’s experience. In reading about it my understanding was that they will be like lowquats, blooming in fall and ripening in spring. I have the sweet one. I’m forgetting its name right now. But this season it bloomed in the spring and ripened fruit in the fall. The comquats are just getting ripe enough and juicy enough where they are really delicious. We will find out today what effect 30F has on the fruit because that’s how cold it is this morning. God bless.

Marcus