I’m in 7b, but have not tried. I know Steve here pushes a bit with his greenhouse.

I am going to try it. MacKenzie farms has 3gal bearing size trees for a good price. This link makes it seem not too tough: https://www.naturehills.com/blog/post/protecting-in-ground-citrus-and-avocados-zones-7-8-and-9b/ plus we may build a greenhouse in the next year.

I grow Satsumas on the 8b / 9a line in Louisiana (5 varieties including Owari, 6 if you count the one I bought last week) , last month we had one night with a low of 14F (lowest temperature here since the 1980's), I had all of my inground Citrus covered and each had at least 220 watts of either christmas lights or heat lamps on them. The largest tree is about 15 ft tall and 20 ft wide and around 20 years old, the smallest was about 4 ft tall and its second year in the ground. All trees suffered some leaf loss ranging from 30-90%+ and as it stands now I am worried one of the small ones will not make it, it currently has 4 healthy looking leaves on it just above the graft line.

Take that as you will when it comes to required protection in your zone, particularly on near record cold nights. Remember zone numbers are based on average lows not those once in 30-50 year events.

p.s. in your zone I would consider one of the new cold hardy hybrids, perhaps Arctic Frost which is a Satsuma cross released a few years ago by Texas A&M, a Mature Owari may survive a 14F night, unprotected under ideal conditions, but in the real world 14F is a dice roll unprotected, for that matter so is 17F. see https://today.agrilife.org/2015/06/10/arctic-frost-satsuma-mandarin-hybrid-named-new-texas-superstar/

I am adding a Miho Satsuma this year and plan to add an Arctic Frost Satsuma hybrid when they become available here (ACP/HLB quarantine state) next year, as an insurance against one of those 100-500 year freezes.

I'm going to go on the fact that we have a pretty warm microclimate in my yard, and back it up with at least a pop-up greenhouse and covers/heaters/lights as needed. I feel like I should be able to provide temps above the minimum, though I realize that repeated or extended polar vortices might be trouble. It'll be an experiment but I'm willing to try! Supposedly there are people doing it in my area. Thanks everyone for your input! We shall see how it goes.

There is a guy in southern Delaware who covers his in-ground plants with several layers of frost cloth + a layer of heavy clear plastic. He strings C7 or maybe C9 Christmas lights within each plant. Lights are on a Thermocube and turn on around 30 degrees or so. I think he's growing grapefruit, Meyer lemons and satsumas this way.

Whoa! That's amazing. Meyers can't take much colder than 28ish, right? Owari supposedly can go down to 12 or so (briefly, etc.).

So they say, but mine which has been in the ground for 2 years survived 14F with cover and christmas lights with few leaves lost.

The cold hardening process of a citrus tree starts at 55-F or lower. Cold hardening is a time delayed process, so the actual hardening occurs about 2 to 3 weeks after the cold event. Colder temperatures down to, but not including freezing increases the amount of hardening per each cold event, but not the speed with which the hardiness will appear. The tree may be processing several cold events at once. As an example, a tree with no developed hardiness (tender to 32-F) may experience 50 degrees on Nov. 1st., 45 degrees on Nov. 5th., and 45 degrees on Nov. 15, we would expect to see it start to harden, maybe hardy to 29 degrees around November 21, then be hardy perhaps to 25 degrees on Nov. 25, and hardy to 23 degrees on Dec. 1st. The exact number of days between the trigger event and the actual hardening varies a bit with variety and the season. The number of degrees of hardening gained per event will also vary, but that's the pattern. It is critical that the tree be completely dormant, in rest, not growing when the trigger event occurs, or it doesn't work. That is thought to be the reason lemons and limes don't become hardy -- they are almost never completely dormant. (Notes taken from discussion with M. Manners 2012)

Silica, I have read some information that suggest cold hardening in citrus may be related to root temperatures dropping below about 57F

I'm (trying to) grow one in Olympia, WA, zone 8a. Because of the Northern latitude and short growing season (outside temperatures don't really start warming up to citrus temperatures here until mid-May) it's surrounded by an enclosure of transparent plastic sheeting, which I only plan to keep on for half the year. I also have several large gallon water containers within the enclosure as passive protection against freezing.

Unlike everywhere else in the country, the West coast has been unusually mild this Winter. I don't think there has even been a freeze here since a freak light snow event in early November.

Parker Turtle, do you keep up with soil temperature there, Citrus seems to stop growing at soil temperature below about 60F and ideally like soil temperatures in the 80's

see http://www.crec.ifas.ufl.edu/extension/trade_journals/2011/2011_Nov_root_temp.pdf

It’s been a pretty bad winter here for my citrus too. It looks like I’m losing a lot of leaves across the board. We are getting long spells down to -7 or more at night, not warming up much in the day. Aloe Vera in a pot turned to jello last month, and the Meyer lemon next to it has crispy leaves , LOL . Of more concern is my best mandarin, which looks to have lost most of its leaves, ironically perhaps the frost cover is too tightly woven keeping too much heat in during sunny days.

Big challenge for me with winter protection is we get typhoons, which rip off anything not either semi passive or rock solid.

I need to sort out better ways to protect my trees rather than just frost cloth wrapped around like a balloon and a few water bottles around the trunk.

One good thing I figured out this year to recover from winter damage is massive doses of ammonia nitrate crystals sprinkled directly (20-0-0). I was able to recover all of the lost growth and put on new growth. Bad point was that blossoms tend to drop off with such high nitrogen levels, so it needs to be timed well. Not perfect, but better than a near stump all year.

Ike, although, it might be true that cold hardiness can develop in citrus trees, plus tree growth stops when root temperatures reach a low of 59-F, this temperature almost never occurs in subtropical areas such a Florida. Florida soil temperature rarely ever goes more than a degree or two below 70-,

Silica, the research on it that I have seen coming out of Florida centers on the nurseries there that thanks to ACP/HLB are now growing in containers in enclosed structures vs the traditional in ground approach. Being in containers the root temperatures tend to track the air temperature more than traditional in ground citrus.

im growing Meyer lemon and Armstrong Satsuma in ground here in bixby ok. 7a. My technique is similar and based off of the guy Dave mentioned above. 25 C9 lights come on at 38F. I added a small heater that I only use when outside is below 15. The lights can maintain about 15 degrees above outside on their own. So far we have had several nights below 10. Covering is 2 layers of white frost cloth when its below 38 but above 20. Below 20 I add 1 plastic tarp and one green frost cloth. Water bottles are there to just help buffer the temps and add a little heat. Meyer is in full bloom right now.

I plan to graft Miho and Dekopon/Sumo to the armstrong.

mksmth that's awesome! Looks great! I love the info about what you do at various temperatures, that'll be super useful info for next winter.

Wow nice to see the determination to help those citrus take to the ground! I might try it but first I would take a cutting and root it just as a backup before planting it in my backyard. I have a satsuma, but don't remember the type. The local nursery here in Pineville, NC did say it was zone tolerant. Its in my garage under lights during winters for the last 2+ years and just noticed it has like lot of flower buds!

Most citrus is not normally grown on their own roots, though there are some exceptions, such as Meyers lemons where I have read that nearly half the plants sold are on their own roots vs being grafted to some type of root stock.

mksmth

How did your st up work out this year. I would imagine that both your tree got a real bust this spring.

Steve

mksmith The word 'bust' above was supposed to be boost. I really am interested because You and I are the only 2 that are using a removable greenhouse for citrus growing far north of the mandarin dekopon line

Does anyone have any advice for growing Arctic Frost, Tville Cintranquat, and Yuzu in Zone 5B? I plan on growing them in pots and placing them in our large high tunnel. I would then have to wrap them in a frost cloth and put Christmas light on them. How much do those Christmas lights give off in heat usually? Are we talking a few degrees or more than 10? I am trying to see if this is even viable, or if Ill need to do some minimal space heating.

Thanks

Today's Xmas lights are mostly led so they don't really give off any heat. You have to find the old school incandescent lights for them to give off any heat. If they are potted why not just bring them inside for winter? Not sure exactly what your tunnel is, how cold does it get in there?

The tunnel is a greenhouse made of plastic material. It is just a metal framing with plastic pulled over the top. Basically, it'll make my 5b climate feel like 6b or 7a inside. i dont have room in the house for as many citrus as I would like to grow.

Daytime solar heat gain with clear greenhouse film can be excessive, therefore white overwintering film is preferred. Nighttime heat loss is dramatic, covering lower trees with frost cloth is helpful, but the cloth needs cover the tops of the trees, not be tied to the trunks. The idea is to allow warmth to continue rising from the soil and use the frost cloth as a barrier to trap the warmth within the space the trees located. The cloth can surround the top of the trees, but not the bottom.