Early Hard Freeze, Before Frosts?!

hemmy

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In NE KS, Zone 5, we have barely gotten below 40F. I’ve only brought the tropicals in twice, before they come in for the rest of the season this weekend.

But we are supposed to have 30F, 23F, and 24F lows early next week. I plan to have conifers and deciduous trees sheltered in the block cold frame, since my former SoCal trees haven’t seen any sub-40s to get acclimated yet this year.

How dangerous to a tree are early hard freezes without earlier frosts?

What does a hard freeze do to the leaves for color? I’d assume 23-24F would cause leaf drop pretty quick. I don’t really have any fall color and even the landscape is only just starting to turn. My Cedar Elm is dark green still, the tridents are a lighter green with some faint color on some leaves.


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ShadyStump

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This is a common thing around here, too. A couple years ago we saw 80s all the way into the first week of October, then 20s and several inches of snow on green leaves.

So long as your roots don't freeze, you'll see all your foliage chilblained and fall off without turning colors, but the trees should be safe. You may lose some of the new softwood growth from this summer on some trees, but not likely anything serious or that would require a restyle. They'll all go dormant after that.
If you can get them some protection from southwestern sun, that will help. The huge temp swings from hard freezes at night then to hot direct sun the next day can really shock the hell out of them, and cause lots of damage. The most reliable course of action is to protect against that bright sun so they stay cold and dormant.
 

Leo in N E Illinois

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Bring in or protect the So Cal trees for the 23 F and 24 F but keep as close to. 32 F on those nights as possible. Then put back out for the 27 F and above nights. A month of these 27 F to 39F nights will get the metabolism set for winter. One or two nights at 70 F can undo the adaptation, so don't over protect. Cold nights help the metabolism switch over to winter dormancy. It takes a month or two of steadily decreasing night temps to get full winter hardiness.
 

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I've had it happen here too when we really didn't have a cool fall and all of a sudden it was going to be below 30. Hate it :mad:

If I had that temperature fluctuation coming. I'd be moving all my azaleas and deciduous into the coldframe at least
 
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Colorado

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Personally I would be protecting pretty much all trees with that weather forecast. The trees don’t have full winter hardiness yet - not even close. 23F could easily kill a small tree that has not acclimated to winter yet. Small pots will freeze solid if it’s 23F for a few hours.

Of course, I wouldn’t blink an eye at 23F in December or January, but this is totally different.

Just my 2 cents…
 

hemmy

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Full freak out mode here. Barely had a 38F a week ago and now we are nose diving over 3 nights straight to 18F!

I understand the argument for not resetting the dormancy process. But it’s hitting 80F, 2 days later. I think I get my 1st taste of the massive shuffle, because everything is coming inside (especially the tomatoes!).

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ShadyStump

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Full freak out mode here. Barely had a 38F a week ago and now we are nose diving over 3 nights straight to 18F!

I understand the argument for not resetting the dormancy process. But it’s hitting 80F, 2 days later. I think I get my 1st taste of the massive shuffle, because everything is coming inside (especially the tomatoes!).

View attachment 459453
Good old bonsai two step.
A month of lows in the 40s will have started the process of going dormant. I would see about temporary space in the garage or something if at all possible.
 

Dav4

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Full freak out mode here. Barely had a 38F a week ago and now we are nose diving over 3 nights straight to 18F!

I understand the argument for not resetting the dormancy process. But it’s hitting 80F, 2 days later. I think I get my 1st taste of the massive shuffle, because everything is coming inside (especially the tomatoes!).

View attachment 459453
I had this happen in N GA a few years ago. No temps below upper 30's for the entire fall, then one night it fell straight down to 18 F in mid Novemeber. The trees were all on the ground with pots packed together... all was fine. Of course, last year, I moved my entire collection from 7b GA to 6A MI the week before Thanksgiving. The temps went from a low GA temp of 38 F in October to a low of 22 F 2 days after we arrived in MI. Again, all trees were fine, excluding a trident and water elm I'm convinced dried out and were dead before getting on the moving truck. Granted, my trees had an extra month of fall to improve their cold hardiness. If you're able, moving them to a somewhat protected area makes sense. Still, cold hardy trees are pretty resilient, even if they've been coddled in N GA or S CA their entire life!

Getting the trees on the ground and packed together will keep the pot soil from freezing all the way through, even with temps that low. Don't forget that it'll only be that cold for an hour or two in the AM and the ground isn't frozen yet so it'll serve as a nice heat source... and if you think this is stressful, wait until spring when this happens ansd half your collection has already broken dormancy and has been re-potted!
 

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Yep. The move from So Cal is a bit more drastic in this case.

For the first concern is protecting the roots through the winter, not being as well adapted to harsh and below freezing as the trunk and branches. Watering just before an expected freeze can hold the root temperature around 32F. Also after for hydration. Grounding and huddling the trees is a great first step.

Second, moderate temperature fluctuations. Freezing in fall and early warm snaps in spring. These are the times most short term damage occurs. Nowadays unseasonal warm snaps breaking dormancy seem to cause more visible damage.

Finally protect the trees from the prevailing wind (especially that KS wind!) and direct sunlight.

Drilling down, assess each individual tree species in the collection and set up a rough level of priority on which species will need the most protection etc. These would be the first to shuffle. (Using the ”huddle method” these should be in the middle of the lot.)

Good luck!
DSD sends
 

hemmy

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Thanks for the words of encouragement for this winter neophyte!

I’m working on 2 cold frames for when “real” winter starts. Concrete block and the other a block and insulated wood box. Both on the north sides in full shade. I’m going overkill and putting in a heating cable floor. Just for those infrequent sub-zero artic blasts and then in Spring to get a head start on root growth and conifer repotting.
 

ShadyStump

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Thanks for the words of encouragement for this winter neophyte!

I’m working on 2 cold frames for when “real” winter starts. Concrete block and the other a block and insulated wood box. Both on the north sides in full shade. I’m going overkill and putting in a heating cable floor. Just for those infrequent sub-zero artic blasts and then in Spring to get a head start on root growth and conifer repotting.
That heating cable will help you get a jump on root growth, but also add to the potential for breaking dormancy early. If you see anything waking up before late March, you'll definitely need to be shuffling them around probably through May.
I think your best bet is to use it only in the sun zero circumstances, then remove the mulch around the pots about March. You'll be out of the extreme danger season, and the warmer weather will start warming up the roots on its own, but very slowly. You'll only have to two step in May that way, and only a few times.
 

Deep Sea Diver

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Yeah... I'm askance about using heating cables. They can be ineffective. Two issues

First of all the system needs a weather resistant thermostat so you can dial in the temperature max to about 40F and minimum of 32F. Placement of the thermister probe will be a challenge.

One might check with @JudyB thread on her cold greenhouse thread. She might have used a max/min thermostat. All mine are minimum threshold only.

Another key is to properly construct the media surrounding the pots and position the cables so the cables actually provide an effective heat source... and that's no easy feat. For example using bark will just insulate the cables.

Using smaller pumice in an insulated box (Ryan Neil idea) might work, but it likely would have to be moist.... and the other measures used to keep the bonsai protected from the element might work to concentrate the moisture on the trees.

Finally, even with the temperature low with a thermostat might partially unfreeze the bottom roots in the pots and not the entire media within the pot, causing possible freeze thaw issues when the outside temperatures get extreme one way or the other.

You might PM @August44 about his experiences with these items and find that Ryan Neil video.

cheers
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hemmy

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That heating cable will help you get a jump on root growth, but also add to the potential for breaking dormancy early. If you see anything waking up before late March, you'll definitely need to be shuffling them around probably through May.
I think your best bet is to use it only in the sun zero circumstances, then remove the mulch around the pots about March. You'll be out of the extreme danger season, and the warmer weather will start warming up the roots on its own, but very slowly. You'll only have to two step in May that way, and only a few times.
Thanks. I think I would only use the cables in extreme circumstances. For the early repotting, I figured it would only be for the pines. Plus one cold frame might not get the cables, as I just discovered that the only outdoor outlet nearby isn't powered.


Yeah... I'm askance about using heating cables. They can be ineffective. Two issues

First of all the system needs a weather resistant thermostat so you can dial in the temperature max to about 40F and minimum of 32F. Placement of the thermister probe will be a challenge.

One might check with @JudyB thread on her cold greenhouse thread. She might have used a max/min thermostat. All mine are minimum threshold only.

Another key is to properly construct the media surrounding the pots and position the cables so the cables actually provide an effective heat source... and that's no easy feat. For example using bark will just insulate the cables.

Using smaller pumice in an insulated box (Ryan Neil idea) might work, but it likely would have to be moist.... and the other measures used to keep the bonsai protected from the element might work to concentrate the moisture on the trees.

Finally, even with the temperature low with a thermostat might partially unfreeze the bottom roots in the pots and not the entire media within the pot, causing possible freeze thaw issues when the outside temperatures get extreme one way or the other.

You might PM @August44 about his experiences with these items and find that Ryan Neil video.

cheers
DSD sends
Thank you. I've watched the video, their heat bed is also in a greenhouse. So they have greater control over the ambient temps also. I'm sure not using my precious supply of pumice that I brought from California on a heat bed! lol.

I have access to expanded shale 1/4" minus, but it doesn't hold water like pumice. It seems like most bulk sand is pretty fine and might trap too much moisture. The only other time I overwintered trees, I dug down 2 feet next to a foundation and built up concrete blocks covered with plastic and used a regular 100W(?) bulb on those coldest nights. I don't think it ever froze. I was also reading about putting coldframes on manure piles, but I don't think the family would appreciate a pile of manure on the patio.

Thx
 

hemmy

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So long as your roots don't freeze, you'll see all your foliage chilblained and fall off without turning colors, but the trees should be safe.
I did the shuffle last year and got some ok Fall colors. Well, I didn’t do the shuffle this year and it looks like freeze damage on the tridents instead of Fall color! But the Chinese Elms, Cedar Elms, and deciduous oaks didn’t appear to have any damage. The cork bark oak also stayed out with overnight lows of 25-29F. My thermometer was off the ground but under the bench so I suspect the air temp dropped a little below 29F. The Gingko was starting to get there but froze also.
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Deep Sea Diver

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Looks like your set up really helped the trees make it through last winter!

Last week our area had four early morning freeze cycles in a row. Just a nudge towards the wintry weather soon to come.

Luckily we had the greenhouses cleaned and shelves ready and the cold frame up. Now it’s just one torrential rain event after another. So the top of the cold frame is off and the trees in the greenhouse are taking shifts to go in out in the rain. At this point we‘d rather have the plants get natural rain water, but mostly stay inside and extend the growing season (for those that can).

Can see your azalea in the background of the gingko image also got a bit of a nudge towards dropping their inner leaves with this event.

Azaleas can take losing their inner leaves….after all, these spring leaves drop anyways. It’s when the tips get frozen that the buds get blasted and the plants themselves begin to get damaged.

Cheers
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ShadyStump

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@hemmy your trees will likely be fine. You'd have done better to have them on the ground, but you haven't hit anything extreme for any of those species.
We had a good snow storm a week ago, and all the trees in town look like that. It's common around here, and even the "barely within their zone" trees survive decently.
 

hemmy

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You'd have done better to have them on the ground,
I don’t have a spot to go directly on the ground that is safe from rabbits. But that would have only protected the roots? The rest of the frost susceptible plants in the ground all died back.

I’d like to get a nice ponderosa pine bonsai. My overwintering for the JBPs would probably be too much for the Pondo. I’m running out of space directly against the house on the north side. But I do have benches on the north side that are shaded in the winter with the lower sun angle. I was thinking I could just stack concrete blocks in a rectangle to limit the rodents and mulch the trees on the ground. Would that protect against a couple days of -5 to -10F? Or would they need additional protection for the “polar vortexes”?

My outdoor insulated winter storages stayed 20-25F during the last sub-zero event. But they were also wrapped in blankets and thick plastic.
 

Deep Sea Diver

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Not sure about this as concrete has a low R value. Likely need to add insulating material on the outside walls to keep the air temperature up during really cold spells. Of course, the best bet would be to create a below surface cold frame, similar to your other set up.

Looking for ponderosa, Andy Smith is a good bet.

cheers
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ShadyStump

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When it gets like that you're mostly just crossing your fingers, but overhead protection goes a long way. It'll help trap the heat radiating from the ground.

Your idea of the concrete blocks would only do so much for the likes of rabbits. They can dig under, and jump over. Unless of course you make the wall high enough or have a top on it.

I would set them on the ground under the benches, mulch them in, then wrap the benches in plastic on three sides, or lean pallets or something up around them.
On the ground, mulched in, overhead cover, and break the air from the outside. That's the important part. It could be temporary just for the extreme nights.
 
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