how do you control the heat in there come summer?
We get temps of up to 38C in the summer, I have a fan and both top ends of the greenhouse can be opened up. The sides also roll up to about 4 feet. It is hot but not hot enough to bother the trees.
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It can creep down around 8ft where I am located [z3], and there is plenty of province north of me that eventually turns into permafrost.
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If your greenhouse is closed all winter, just being out of the wind and avoiding dessication will also be a factor. Especially if you are planting in an area where sublimation commonly occurs during the winter months.
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Does your greenhouse moderate the low winter minimums at all, even by a degree or two?
I havenāt kept that close of track during winter but I would guess not, especially at night. I have a remote thermometer in there in the spring and the temperature readings are the same as outside when the sun goes down.
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In SE AB I had westcot apricots, they did well but only produced about every 4th yr. There chinooks were the enemy. When they Did produce you could hardly see the tree for the apricots.
Now in east central Saskatchewan, have both westcot and debbies gold. Nothing yet, they, āsurviveā and I sometimes see a few flowers, but donāt think theyāll do well here. Frankly Iāve about given up on them, only reason I havenāt dug them out is wife still has hope.
Mordon 604 may be worth trying, I couldnāt get any this yr or last but will try if see them. Have read of some being developed in ND that look really promising, but we canāt get them here.
3 var have been developed NW of Regina, donāt know anything about them though, can get them here, if your quick on the button, they sell out Fast: Products ā Prairie Hardy Nursery
Have the siberian c peaches, theyāre tough as nails and grow like weeds. Our 2 yr olds (from the treetime seedlings) are just under 6ā tall. Apparently very late ripening though so not sure if weāll ever get ripe fruit, but figure worth a shot.
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I have Sugar Pearls and Tlor planted. If/when they set fruit, I am willing to share pits with anyone who wants to cull them for cold hardiness by natural selection.
I am technically zone 6b, but more conservatively, zone 6a.
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Any details on who in North Dakota was working on hardy apricots?
i have brookcot, hoyt montrose , harcot and westcot grafted on my black ice plum. all are growing well. ill post how they do once they start fruiting. also have waneta, toka and canadian plum on there. canadian plum has flowers so hoping to see how the fruit is. going to be a interesting tree once everything is producing. wont be long as its been fruiting since its 1st year.
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Believe it is the State of North Dakota.
Could look on St Lawrence nurseries? Or maybe check here: https://www.montanafruittrees.com/
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Your theory about daytime heat in winter inside the greenhouse moderating damage to the trees is interesting. But how much heat is too much? Pulling them out of dormancy too early would be a bad thing. We put a greenhose cover over the roof when we removed the insulation panels in late April. With minimum winter lows of -9C, everything inside looked fantastic. Lapins cherry, apricots, plums and apples were all loaded with fruit buds. Then some warm days in late April and early May got the trees pushing too much. Apricots were at calyx red and cherry also quite advanced.
After a fairly warm day, we had a cold clear night. They were forecasting -4C.
The actual low out at the orchard was -6C. Here is the crazy part. We had several cheap min/max thermometers in the low tunnel that read between about -8C and -10C. Colder than outside? Is that remotely possible?
Due to a health issue, we were unable to put heat on inside which had a lot to do with that severe low. After that, Lapins fruit buds were toast and the tree may be dead to boot. Pears look dead. Lots of dead looking branches on the apricots, plums and apples. It is a lot harder to manage the temps than we bargained on.
What are you using to heat your greenhouse and how large is it?
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thatās why i gave up on a unheated greenhouse here in n. Maine. the sun would heat it up enough to take the plants out of dormancy enough that a cold night would kill / damage them. why anyone that has tried greenhouses in the past here have given up on them. my father made it work years ago with a old trailer furnace to kick in on the cold nights but was pretty expensive just to get a couple more months of grow time.
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@steveb4 Thanks for sharing your experience. There are people who do it successfully but it seems everything has to be executed perfectly to avoid killing not only fruit buds but also the trees themselves. Serious heating requirements, but also ventilation challenges especially for us because our ālow tunnelā has a high ratio of surface area (which is related to heat gain where the sun is shining) to inside volume. We have seen temps up to 120F when the fans didnāt come on. We were unprepared for that. The erratic weather we had in late April and early May didnāt help. Donāt think that I can ever remember having days in early May at 97, 98F here in Winnipeg. Anyway, looks like we have completely lost several pears, Lapins cherry, one apple (Holstein) and lost 3/4 of the branches on one apricot (Haroblush) that is not very hardy. One the other hand, Debbies Gold apricot seemed unphased, other than no fruit set despite flowering profusely. And a Westcot apricot seedling was much less damaged than Haroblush despite the seedling fruit buds having been much more advanced than Haroblush at the time or the freeze. Live and learn.
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the university here has one of those automated, temperature controlled greenhouses and it grows great but its 20ā x 40 at a cost of $25000 . but the power goes out and your plants are toast. places like Finland grow alot of their veggies in greenhouses , like the one i mentioned here, and are a substantial investment that most cant afford. being northern growers , we cant help fantasizing though . 
i think it would also be beneficial to grow less hardy fruits in a greenhouse as it takes more heat to take the trees out of dormancy compared to the more cold hardy ones. but then you would have to make sure they dont get too cold when it hits -40.
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I have never had a year yet that pulled my trees in the greenhouse out of dormancy too early. Here in Zone 2 the daytime warming in the winter is not high. Our sun is so low on the horizon and so weak that it doesnāt seem to pose a problem. By the time I start my greenhouse up the beginning of April we still can have -20C weather. Once I decide that it is time they came out of dormancy I fire up the radiant heat and after that it never goes below zero.
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I know, I know, Iām in 5B.
But for what itās worth, Iām trialing the following:
Tilton & Harcot apricots
Harko nectarine
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Try plums. Black Ice, Toka and Superior are good to zone 3
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Ordered a Toka and Lavina both on Myrobalan.
Weāll see how they do!
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Hello Fellow Manitoban. Could you tell me were you got your scions for Zard, Precious and Montrose and rest? Also would you sell me a stick of each this march? Thanks
I have a Casino, Capilano, Morden 604, Westcot, Open pollinated Seedling of Bakers Gold (cling stone) also Will have a Debbies Gold in spring and a Artic Dusk. Few Manchurian seedling(s) from seed, unknown prairie variety.