Frank:

You are in mid winter so the hardiness potential of the trees is near peak. The most important factor at this point is your weather over the last month. Every day that it stays continuously below freezing, the hardiness of the fruit buds increases by 1F until maximum hardiness for the current dormancy state. Every day where it gets above freezing, hardiness decreases by 1F. So look at your weather the last month.

My weather data says you have only had 3 days where it got above 32F since Dec 1, yikes!!!! No wonder I moved south!!!! Anyway your trees are as hardy as they can possibly achieve.

Amazingly fruit buds near bloom also react much the same to prior weather. I've read this to be true and have seen unusual hardiness around bloom if the weather has been in 33-45F range for several days prior to a freeze.

The probable mechanism for these changes is that the tree reacts by lowering it's water content and/or increasing soluable solids in the buds.

Its been nasty here. Just non stop cold and snow. I really wish I lived right next to Lake Michigan... Milwaukee hasn't been below 0F in over 400 days or something like that (last winter they didn't go below 0F...I sit at roughly the same latitude and i've been below 0F 20x last winter and 8x so far this winter).

Hopefully we don't drop much below -20F so I can eat apricots this spring :)

The lakes do help. They moderate the extreme cold air as it passes over them AND they generate a lot of cloud cover that traps the heat. A couple of nights ago, it fell to about -5 to -8 air temps over s. central lower Michigan (Jackson, Coldwater, Hillsdale, that area) under clear skies. I had lake effect clouds streaming off Saginaw Bay to my north, and it only fell to about +7 or +8 here in Oakland County.

Yup. A online friend lives just north of Milwaukee...basically directly east of me about 200 miles or so. Most clear nights, it seems he is 15F+ warmer then me. The lake is an amazing source of winter heat (and a reason why Door County can grow sweet cherries/Michigan can grow peaches/etc).

I'm most worried about the 3 Tomcot trees. I'd hate to lose the buds on those trees. From reading its suggested that some 'cots can handle -30F... We'll find out i guess.

Newest model run still showing -26F for here, although that does usually have a cold bias.

Some people have suggested Christmas lights or a light bulb under plastic sheeting. I've never tried it. Just to traipse through all the snow to get to my trees would be an undertaking, so they have to tough it out on their own till spring now. Northwoodswis

Wow Frank, suddenly Sheboygan doesn't seem so bad! I'm starting to rethink my plans to move over to your side of the state. Well not really, I'll make it over there someday.....when I have a greenhouse ready to go!

Hang in there,
Little John

Newest/freshest model run shows -30F here.............. Not good.

Tomcot will be toast at that, or so I would assume.

The warmest areas over here would be to the south around Prairie Du Chien...especially in spring/summer. The crappy thing about lake areas is spring. Any lake wind and its game over, while we can bask in warmth over here (given the snow is GONE!). I believe looking at the charts, that late Feb is when La Crosse starts running WARMER then Milwaukee in averages...that lasts until July (until the lake warms).

I know it's too late to do much about the situation NOW, but I wonder, if you want to continue to try to push the limits, in future years, could you do something with some of your fruit trees like this man does in Utah, where he grows large palms outdoors with winter protection? It would probably work. It requires a foamboard box and some CFC lightbulbs, plus some work, of course.

Here is a link that might be useful: Palms in Utah:

Most fruit varieties come with advice on what zone they are hardy to. That will give you a pretty good idea of what their lowest winter temperature might be.

Apricots can be quite hardy. It's the blossoms that are the problem. They bloom really early and are frost tender. 26 F is about their bottom tolerance, although, I had 21 F last spring and still got a few cots on the tree that was in bloom at that time. I do have lights in my trees in the spring, but still, 21F is too low for the apricot blossoms.

My apricots, peaches, and nectarine trees have survived temps like you are getting. My only freeze damage has been on Stella cherry, when it got into single digits before the trees were dormant. Apricot trees weren't damaged by that.

It's dry cold here. I don't know if that makes any difference. Lots of wind, though.

Den-

I've thought about covering them with tarps just for wind protection (kind of like what people do with arborvitae)...Sometimes I think the drying effects of winter winds can be what kills fruit buds, but i'm not sure.

I'm not too sure what else can be done other then growing in large pots.

What will be interesting is that i have 3 apricots out back that are seed grown California fruits. I'll be interested in seeing if they even leaf out.

Showing -27F on the models, NWS thinks -16F... Quite a bit of difference. I think the NWS thinks the winds will hold up (that causes mixing, which keeps it warmer).

Just for the record, we had temps as cold as -37F here back in 1951...so the chance is always there to kill about everything!

Frank: I had a Blackgold cherry put out a couple blooms 2 years ago after -28 over the winter. I'd only had it a couple years and only saw a few buds on the tree over the winter that looked like they could be flower buds. So, the buds can survive that much cold. However, last winter after a week below freezing in early Oct. with a low of 12, we also bottomed out in Dec. and again in January at -28, and I lost the entire above ground portion of the tree, from what I presume was vascular damage as everything looked alive in spring, but then just slowly dried out and never grew.

I guess you can pick the year to decide what the maximum low to damage the tree will be.

Fruitnut, where did you find the data about every day above freezing decreases hardening by 1 degree. That seems very suspicious to me as plenty of areas have winter days that mostly rise above freezing all winter long. Are you sure you're not talking about when lowest temps of the day exceed freezing?

Harvestman:

It was written up in The Good Fruit Grower some time back. I'm quite sure they were talking about the daily Max having this effect. What I don't remember, and what matters quite a bit, is over what range this happens. It's not an endless increase in hardiness. I would suspect that it's a matter of 10-15 maybe 20F at most. So fruit buds in WI with temperatures continuously below freezing might achieve a maximum hardiness 10-15F lower than down here with nearly every day above freezing but below freezing at night.

The maximum hardiness that fruit buds can achieve increases rapidly in fall and peaks in mid winter. Then it decreases through bloom.

Hi Frank,

What source do you use for the models? Is it online?

-Larry

Fruitnut, I've read a lot about the hardening off process over the years, just somehow missed the info I asked you about. If it was published in the last few years I will probably be able to find the article on line. It's seems kind of counter intuitive to me so I'd really like to find the source.

Well I may have escaped one. Ended up at -19.7F in my backyard. That should be borderline for my peach trees. Hopefully this is the coldest reading for the year.

harvestman:

I found an article that discusses this issue. Like most things it is way more complicated than I stated. It looks like 18-40F is best to induce hardiness, with 28F optimum. This cold induced hardiness is only possible during certain physiological stages of the rest cycle. Perhaps you will read it and get it right for us. I'm too busy today, gotta run.

Search on: good fruit grower tree condition and cold tolerance delmer ketchie. I think you will find it.

Thanks Fruitnut. I think you already got it "right enough for us" for all practical purposes but I'll read it this evening to see if I can get it straight in my own head. I'm sure you realize that you're a great contributor here and your contributions to our understanding is unsurpassed on this forum, IMO.

One reason to grow fruit along Lake Michigan:

Milwaukee's Mitchell Field ended a 733 day stretch (more than 2 years) since the temperatures dropped to zero or below. This was the record longest stretch of days above zero for the city. The next longest streak was 422 days ending in March of 2002.

Milwaukee dropped to -5F. International Falls, MN dropped to -46F, which is a new record.

I once applied for a job up in International Falls. This is one of the days I am extremely grateful that I didn't get it. Madison didn't get that cold, I can't find the exact number but it looks like it was around -10F.

Yup, here in NY it's forecast in my area to get down to-8 which is low as it's been for several years. 10 years ago that wouldn't be considered unusual here, however, and between -10 and -15 was a common lowest winter temp.

It is easy when reading the catalogs to get caught up with the glowing descriptions of a certain fruit and want to chance it on hardiness, but I find it gives one a more relaxing winter to pick varieties a zone or two hardier than the zone in which one lives. Anything else should just be considered experimental or a bonus when it produces fruit, but don't get attached to it. Then one can sit inside and not fret on those -20ðF. nights like last night was here. It's easy to imagine when purchasing the nursery stock that you will do all sorts of elaborate protective care, but then things can come up in the fall that prevent you from getting around to it some years. I was going to shovel snow over my tenderer varieties of blueberries again this year (which worked wonderfully the previous winter), but it turned out I was out-of-state for several months in the late fall, and when I returned, the snow was already too deep to get to the ridgetop garden very easily, so they will have to tough it out on their own. At least the lower 18 inches are protected, so the bushes should survive, even if they bear no fruit on the upper branches. I once imagined I would cover my young Sugar Pearl and Westcot apricot trees with tarps and use Christmas lights in the spring, but fat chance there, too! Northwoodswis