do not wrap the trees. They are evergreen and do not go dormant. There are varieties that can go down below 20 F/-6 C. The problem you face is all of them ripen in November through march and -1 C destroys the fruit. Your best chance is to get the tree to flower and grow very early in a greenhouse when the sun is getting higher. and the days are lengthening with extra light so that the fruit ripens in September/October when the sun is high. Trying to extend the year in November/December is futile because there is no sun to work with in the fall

That's very interesting. I got some nice fruit off them last year, but they were all just bought from the garden center, so who knows how they were treated to get that? This year should be decisive.

Hmmm, green housing them means back into pots, which I can't do now.

I've heard of some citrus growing outdoors ok here, one person used a sheet to stop frost?

They need the leaves to produce the energy to make the flavor. The same thing happens with other fruit, like blueberries - sometimes something goes wrong and the leaves fall off while the plant blooms and makes berries. Without leaves the berries rarely ripen and even if they do they have no flavor.

I would look for the type of citrus with the earliest ripening schedule - probably some sort of Satsuma. Then try and plant them with a wall nearby for winter wind protection. My Owari Satsuma ripens around October, sometimes September and they are pretty hardy. I'm in zone 7b. We've had severe winters the last two years so I dug my trees up and keep them in pots now (they are small).

I have to add that I spent my childhood living in Japan. My parents were from small towns here and dreamed of living in a large city/foreign country so back in the 60's we moved to the suburbs of Tokyo where I lived until high school. We weren't military but because of my dad's job we were allowed to go to school at the nearby Air Force Base. I loved living there and even now I consider Japan my "second" homeland.

You can raise the soil temperature by up to 10 Celsius by covering the ground with double layer plastic and watering with warm water 50 Celsius when last frost safety. The trees will start out much faster in spring and should carry over to fall.

In Cincinnati our useful growing ends mate September but my citrus fruit would often survive till late November for safe picking. We may get several frost just below freezing that would not hurt the fruit or tree.

Interesting concepts guys I'll have to try. Currently I have a couple of mikan varieties, yuzu, ureka lemon, navel orange, shikwasa, sudachi, kabosu. These last 2 are native to the coast not far away, although the colder winters here I'm sure will affect. These 2 and the lemons would be great to thrive if they can.

Trianglejohn, I'd love to hear all your experiences some time. Feel free to drop me a line anytime. I've lived here most of the time since 1999.

I know its possible if you bring the plants indoors. I'm not sure if you have them in the ground or not but it seems like you might be right on the edge of where Citrus can be cultivated exclusively outdoors. Otherwise producing fruit that appears and Tate is a good can be done in the far north but cultivars that will do so without requiring more heat than can be provided is something to watch for. Otherwise, Mobile man when the average low gets around 55 and regardless of ambient light it's getting through windows augment enough metal halide raise and you will be producing fruit regardless of where you're at. Or I should say how far north you are or how short your growing season is.

One other thing I forgot to mention is that if you do move plants indoors, citrus trees specifically will drop leaves and fruit if the difference between the conditions indoors not match closely what it is currently experiencing outside. So if you have trees with fruit that is already set moving them in early enough before bills implement changes occur will ensure the city continuation of any fruit maturation you might be experiencing. Despite a arid nature or characteristic of many Citrus, they will drop leaves if you move them indoors a humidifier. It just gets so dry inside in the North that some leaf drop is expected anyway, dependent upon the variety. Radiators or any indoor heating element , bass hitting anything, will promote leave drop in Citrus.

niceguy, when do you actually get your freezing nights? I'm guessing they don't typically come until late winter? I lived in Osaka for a time, and remember how nice the weather was right up through November. There were lots of satsumas grown in the area, but I think they ripened before the coldest weather hit.

Of course, it sounds like since you are in the mountains you probably get colder than Osaka, but maybe the timing of it would allow you to be successful?

I gave up on the indoor/outdoor citrus thing. Too much work and trouble with scale insects for a few citrus that were already cheap in the market. But if I could grow even the most cold hardy types in the ground where I live, I totally would.

You only need a tiny bit of protection to get the trees through it.

Instead of wrapping them, make a frame to hold a frost cover cloth above the foliage and put the cover on when you need it. Then put a few incandescent bulbs or strings of incandescent (not LED) fairy lights under the tree during the predicted freeze nights.

The problem with freezing damage is not only that the fruits that should be ripening are killed, but if it's too severe you also lose the next year's flower buds.