Man, That's Cold

I received an e-mail from a new friend of mine named Claudia. She also writes a good Blog, Gardening Naturally with Claudia. You can check her blog out at:
http://gardeningnaturallywithclaudia.blogspot.com
She asked me a question that I never really gave much thought to, So I figured it would be a good subject for today's posting. She lives in Zone 5b (-10 to -15 Fahrenheit) Man, That's Cold!! She wanted to know what Citrus would be hardy in her climate. There is not much, BUT, there are some!
With that being said, let me give a few insights. Factors affecting hardiness are of course, minimum temperatures, how long it is, weather before the freeze, soil moisture and wind protection.
I have touched on some of this in other postings, but will revisit them here. Minimum temperature goes without saying, -10 to -15 is pretty cold.


As you can see from the above map, that kind of temperature and colder covers about one fourth of the country. So most of the ones I will list can be grown even further South.
How long the freeze is: One night of freeze may not hurt a plant too much, a week (or longer) could be another story.
The weather before the event: If you have had very cool temperatures and it has been rather consistent, that is a lot better than warm for a few days then a wicked cold spell.
Soil Moisture: Make sure plants are well watered before the event, the wind also falls under here. Cold and wind dry plants out. A dry plant is much more apt to be hurt by a freeze than a well watered one.

Now, as for Citrus that can handle that kind of cold. There is really only one for a Zone 5b. Poncirus trifoliata. It is hardy to about -15F There are two cultivars, a straight one with straight thorns and branches and ones with curved branches and thorns called 'Flying Dragon'.
This is one of the few actual deciduous (loses it leaves) Citrus. The best way to describe the fruit from this tree? I got this from the book 'Hardy Citrus for the Southeast' By Tom McClendon. He writes, "The fruit are edible, meaning that you won't die from eating them". That pretty much is the best description I can come up with other than, if you don't mind the taste of kerosene, this fruit is great! Tom also has uses listed for the Trifoliates: Hybridization, Ornamental and TARGET PRACTICE.
If you are willing to provide a little protection, maybe plant on the South side of your house and very close to a building or wall, you could grow some of these: Hardy to about 5F.
Citrandin (Poncirus X Citrus reticulata)
Citrange (Poncirus X Citrus sinensis)
Citrumelo ( Poncirus X Citrus paradisi)
Nansho Daidai Sour Orange (Citrus taiwanica)
Some of these may be palatable to you. I have actually had a decent Nansho Daidai. I also enjoy Sour Gummy Worms, so take that into consideration.

If you can protect down to about 10 degrees the list gets much better:
Bloomsweet Grapefruit
Yuzu (as seen on Martha Stewart)
Yuzu Hybrids
Nippon Orangequat
Changsha Mandarin
Juanita Tangerine
And actually there are many others.

Down to about 15 degrees and you are getting into the:
Kumquats and their Hybrids (Sunquat, Procimequat, etc.)
Calamandarin
Sour Oranges

Your Satsumas are in the upper teens, I don't recommend pushing these there though. I try to keep them no lower than mid to upper 20's along with:
Sweet Oranges
Meyer Lemon
Grapefruits

Like I said in the beginning, there are a LOT of factors that will effect cold hardiness. There are other steps that you can take to protect them.
Build a mini greenhouse over them. Grow them in Containers. I actually could go on for hours talking about this subject alone. Hopefully this gives you some ideas to try. Finding many of these varieties may prove to be difficult. There are some websites that you might be able to find some of them. Pick a couple and do a Google search. Later, I will do a post on finding some Citrus online, I have some great friends and will give you their websites. That my friends will be for later, for now you have to wait and come back often! LOL
Happy Growing!
Darren