Quercus Suber winter protection

I picked up a cork bark oak this past spring, and it's grown well and quickly this year. It was repotted early spring, and is currently wired for the second time this year. (it grows that fast!) I was planning on overwintering this tree in my cold greenhouse, temps between 28-40, but with heat mats as well for root protection. Heat mats under the less hardy trees are kept warm enough so the pots don't freeze solid. I wonder if anyone growing these in colder climates can tell me if this is going to be enough protection.
I have experience keeping my EU. olive inside to overwinter, and am wondering if that might be the better option.
Do these trees need to have a dormant period? If not, I may go with the inside option, it works very well for the olive.
Thanks for any input!

This makes for more than one Ohioan looking for the best way to overwinter these. Mines too has grown well this year. Besides heat mats.....would an unheated garage work with heat mats?

Cork oak (Q suber) grows in the same climates as olive (Olea) so the same treatment would likely work.

In 2012 I bought 2 seedling Q. suber, cork oak. I left it out until a light frost, but did not let it get cold enough to defoliate it. I think I brought it in before dropping to +27 F (wamer than -4 C) then ran it under lights as a tropical. Seemed to work out ok. Not much growth at all in winter. A trial of one year does not make me an experienced grower of cork oak. But that is what worked for me.

I suspect the cork oak can take a little more cold than what I allowed it to experience, but I have no clue as to how much more cold it will take.

Middle of July I chopped one of the seedlings down to 3 inches tall, and was rewarded with a burst of new growth about 3 weeks later. I was amazed at how well it back budded. I think I will use the grow out and hard chop back for the next decade, or until the trunk is thick enough. Looks to work well.

Thanks Leo, I'd already made that choice as we are already at 25 at night here. I think that I may defoliate too.
I don't think that they need dormancy, and I'd rather be safe....

Mitch and Judy, glad your trees are doing well.

- bob

JudyB wrote:Thanks Leo, I'd already made that choice as we are already at 25 at night here.  I think that I may defoliate too.
I don't think that they need dormancy, and I'd rather be safe....

I am just curious where this 'defoliate for freeze tolerance' thinking comes from. Do you pluck all the needles off your pines/spruce/fir to get them through the winter? Cork oaks are broad leafed evergreens.

I'd read that (defoliating for dormancy) a few places, but since asked the question, and now seems like a bad idea to defoliate.
I'm also still debating on keeping this like a tropical. Bob, do you have any suggestions for Mitch and I? It's been a pretty even split - some saying temps under 40 will kill it, and some saying keeping like a tropical will do it in...
Although Leo has actual experience to back up the inside idea.

I'm not sure that defoliating is something that would be helpful as far as winter care goes. I think trees are pretty good at knowing whether they should drop their leaves or not. And I believe that trees do pull resources out of the leaves before they drop, so cutting them before that process would deprive the tree a bit.

Obviously my winter experience is quite different from yours, so I can not give you any advice from personal experience. My teacher Brent has some of these, and it gets colder at his place - he can get freezes into the 20s. As far as I am aware, he does not give them any extra protection over and above his other trees, but I will send him a note and see if he has any specific advice.

- bob

Judy,

my own came from Florence. It slowly faded, I should have used a refrigerator, miss it, memories.
I think Anthony may have mentioned that to you.
Later.
Khaimraj

Yes Anthony did tell me of your sad loss of the oak. I don't wish to suffer the same fate, so I'm trying to find a happy medium. I am hoping that the greenhouse temps I can keep will be sufficient. I will find out this winter if it's possible, as I've decided to go with the outside plan.

Bob, if you do speak with Brent, that would be great! Does he get sustained lows for any length of time where he is?

Thanks for all the responses, maybe once I guinea pig this winter, this tree can become more widely used, as it's a really wonderful tree to work with. I'll be looking for other oaks to work with as well.

I heard back from Brent. He says that cork oaks can handle temps down to 15-20 degrees F, but will likely defoliate at those lower temps. So if you can have some sort of cold frame that can keep temps above that zone, you should be OK

- bob

Then it sounds positive about my setup inside my garage. It is situated near but not at the window among other more hardy trees. I have this small space insulated with panels all along where the cold can get in what used to be a dog cage inside. The space heater kept the area no lower than 20 last winter and the coldest outside I recall was down to 3 degrees F. Also, its on a heat bed so that should definitely help the tree?? Reading this info, I think I can feel more comfortable on its survival.

cbobgo wrote:I heard back from Brent.  He says that cork oaks can handle temps down to 15-20 degrees F, but will likely defoliate at those lower temps.  So if you can have some sort of cold frame that can keep temps above that zone, you should be OK

- bob

In my limited experience, cork oak, Q. suber and one of the shrubby live (evergreen) oaks from seed from south of Las Vegas, Nevada. They do not do well in my climate, (zone 5) if it gets so cold they are defoliated. Lost my Las Vegas area live oaks over a cold winter. I think it might be a combination of the actual cold and duration of the cold up this far north. Winter is a lot shorter along the Mediterranean, and in California. I'm running them as "sub-tropicals' for the winter. They are in the light garden with the orchids. Mostly because that is what is easiest for me. I did let them get a couple light frosts.