When To Remove Conifers/Evergreens from Unheated Garage as Winter Closes (?)

Bonsai Forest · Feb 5, 2024

The daily temps here in Charlottesville VA are consistently 50s to low-60s with overnight and twilight temps reaching the low-to-mid 30s.

As a cautious approach, I’ve kept my trees grouped on the floor in the unheated garage with low levels of natural sunlight passing through in the mornings and afternoons. But I’m curious as to when is the safe/optimal time to remove them from the garage to remain outside for 2024.

Is it generally unsafe for the trees to “exit dormancy,” have exposure to warm daily temps but then experience low 30s F overnight? Would this be a serious detriment to their health and set them up poorly for 2024 growing cycles?

horibonsai · Feb 5, 2024

The answer is you cannot be sure, but check the last date frost in your area. Having said that, my area is April 1st, and I emptied my cold frame in preparation for repotting, cutting, and grafting trees. I'm going to rely on a strong back and the bonsai shuffle.

Natty Bumppo · Feb 5, 2024

If the trees do fine in Virginia's weather and are still dormant, I wouldn't worry about freezes. If you think the really severe cold is done for the season, I'd say you could take them out anytime. If some break dormancy and begin to open up while it's still winter, you may have to move them back inside if it's going to freeze overnight.
I took my trees into the garage before the deep freeze here a few weeks ago (I live in MO) and have put them back outside in the last week. If my Japanese maple leafs out early again, I'll just move it back and forth if a freeze is expected.

Bonsai Forest · Feb 5, 2024

horibonsai said:
The answer is you cannot be sure, but check the last date frost in your area. Having said that, my area is April 1st, and I emptied my cold frame in preparation for repotting, cutting, and grafting trees. I'm going to rely on a strong back and the bonsai shuffle.

Consulting local weather now. Much appreciated. The Bonsai Shuffle, lol, I understand what this is now.

Bonsai Forest · Feb 5, 2024

Natty Bumppo said:
If the trees do fine in Virginia's weather and are still dormant, I wouldn't worry about freezes. If you think the really severe cold is done for the season, I'd say you could take them out anytime. If some break dormancy and begin to open up while it's still winter, you may have to move them back inside if it's going to freeze overnight.
I took my trees into the garage before the deep freeze here a few weeks ago (I live in MO) and have put them back outside in the last week. If my Japanese maple leafs out early again, I'll just move it back and forth if a freeze is expected.

Much appreciated!

Bonsai Forest · Feb 5, 2024

Interesting, from garden dot org (similar to Almanac):

Frost Dates: First and last frost dates for Charlottesville, VA

As the growing season approaches, the days get longer, the weather begins to warm up, and the nights start being less cold. You're still getting frost, but the chance of nightly frosts gets less and less with each passing day. Eventually, the frost stops, and this is when your tender plants are fully safe. So, how do you plan for this? The probabilities on this page help you assess your risk of frost on any given day.

What's a safe temperature for tender plants? When the nightly temperature falls, frost can form, even above 32°, because the air is colder high above the ground and the frost can form up there and then fall onto your garden and do some damage, even if it's 36° on the ground. So many factors come into play, including wind, concrete, houses, trees, and other structures, etc. Because of all this, you might want to consider 36° as "the danger zone".

In your average springtime, you have a 90% chance that there will be no 36° nights by April 28. In other words, you can pretty much count on being safe from frost by that day. But we want to get those tomatoes in the ground as soon as possible, right? We see that there's still an 80% chance of 36° on April 8, so we don't dare plant that early. We wait a few days and by April 16 we are at the 50/50 point. At this point, we are close and we can start watching the weather forecast. If the upcoming week's forecast doesn't show below 40°, then it's probably okay to risk planting out your plants. If conditions change and a surprise frost does threaten, there are always things you can do to protect plants from frost.

I don't have tomatoes or produce; I have small trees, but perhaps this is the broad threshold across the board for everything. I don't mind doing the 'bonsai shuffle,' so I plan to bring them out before the end of February and begin fertilizing this month (as opposed to March, like last year, knowing now that nutrient uptake begins roughly 3 weeks to a month after application).

But then I plan to do repots, so repot in February???

Source: https://garden.org/apps/frost-dates/Charlottesville,+VA/

Bonsai Nut · Feb 5, 2024

I have left all my conifers outside, every winter since arriving here in NC. Last year we had a cold snap where temps dropped to 5F. Though I lost many decidious, I did not lose a single pine, juniper, cypress, etc.

Bonsai Forest · Feb 5, 2024

Bonsai Nut said:
I have left all my conifers outside, every winter since arriving here in NC. Last year we had a cold snap where temps dropped to 5F. Though I lost many decidious, I did not lose a single pine, juniper, cypress, etc.

I understand. Is it okay, then, to perform repots on my trees toward the end of February here? Whether I "shuffle" them or not?

snowman04 · Feb 5, 2024

Bonsai Nut said:
I have left all my conifers outside, every winter since arriving here in NC. Last year we had a cold snap where temps dropped to 5F. Though I lost many decidious, I did not lose a single pine, juniper, cypress, etc.

This is really good information for us in the colder climates. I will be leaving my conifers outside (ala Walter Pall) next year...

TrevorLarsen · Feb 5, 2024

Bonsai Forest said:
I understand. Is it okay, then, to perform repots on my trees toward the end of February here? Whether I "shuffle" them or not?

If you repot you definitely don’t want it to freeze after since it could kill the newly exposed and stressed roots.

Adamski77 · Feb 5, 2024

Bonsai Nut said:
I have left all my conifers outside, every winter since arriving here in NC. Last year we had a cold snap where temps dropped to 5F. Though I lost many decidious, I did not lose a single pine, juniper, cypress, etc.

I second that... though winters here are not that tough... all conifers out all winter... they are really tough. The only ones that I protect are trees on which I made some bigger work late autumn or during winter.

Hartinez · Feb 5, 2024

I understand the desire to protect and partake in the shuffle. But with conifers and many evergreens, it’s just not necessary in most climates. Even in the coldest conditions. Most can take sub zero temps without batting an eye. I really think the sooner you get to know their thresholds a bit more the less the shuffle becomes a thing you even consider. With that said, delaying repot until the tree tells you it’s ready is best.

Kievnstavick · Feb 5, 2024

People in your locale area could probably give you more specific windows for repotting. The biggest factor will be your aftercare of the trees.

Issues with frost is referring to tender new shoots and leaves that are not adapted to such tempatures. This would mostly fall into the deciduous category or seedlings sprouting. Some deciduous like my blueberries can take a few frosts while putting out new growth without damage since it is slowly coming out of dormancy and is an early bloomer. New shoots on cold-hardy conifers should be fine. Especially opportunistic conifers that tend to get short windows to grow.

When it comes to winter protection, I really only start paying attention to when the tempatures approach 15F. I then just place the trees I am worried about on the ground close to the house to protect it from wind. All of my conifers were left on their benches in 10F weather.

Just remember, these trees were around well before there were unheated garages to store them in

Edit: As it was noted in the previous post. The tree will tell you when it is time to repot if you have the time to read its "body" language.

WNC Bonsai · Feb 5, 2024

One reason I plan to invest in a greenhouse this spring is the vagaries of spring weather these days. We have consistently been seeing earlier warm spells which induce trees to break dormancy followed inevitably by a polar vortex or plain old freeze which brings tmeps down in to the 20s. This has resutled in loss of apple crops down here for the last couple of years. This wreaks havoc with trees that have broken dormancy as well as trees that I have been repotted. My approach has been to put the most sensitive trees in the back of my pickup and back them out of the garage each morning once temps come up above freezing the leave the out all day and back into the garage at sundown. However I can’t keep doing that forever so a greenhouse seems to be the best option to protect the trees until spring arrives for sure. I doubt that Charlottesville is much different from us down here.

Adamski77 · Feb 5, 2024

WNC Bonsai said:
My approach has been to put the most sensitive trees in the back of my pickup and back them out of the garage each morning once temps come up above freezing the leave the out all day and back into the garage at sundown.

I need to get a pickup

Bonsai Forest · Feb 5, 2024

Hartinez said:
I understand the desire to protect and partake in the shuffle. But with conifers and many evergreens, it’s just not necessary in most climates. Even in the coldest conditions. Most can take sub zero temps without batting an eye. I really think the sooner you get to know their thresholds a bit more the less the shuffle becomes a thing you even consider. With that said, delaying repot until the tree tells you it’s ready is best.

The reason I brought them into the unheated garage was the day of 70F and week of high 60s. I thought I understood it as dangerous to health/life to go from 30s to Summer temps then back to 30s overnight. They’ve been consistently at around 40ish thus far since the sudden heat. Perhaps I misunderstood how they’re supposed to transition from winter to spring.

I’m happy to bring them and leave them out if it’s safe and overnight frost or freeze is not a risk while days are warm.

Bonsai Forest · Feb 5, 2024

WNC Bonsai said:
One reason I plan to invest in a greenhouse this spring is the vagaries of spring weather these days. We have consistently been seeing earlier warm spells which induce trees to break dormancy followed inevitably by a polar vortex or plain old freeze which brings tmeps down in to the 20s. This has resutled in loss of apple crops down here for the last couple of years. This wreaks havoc with trees that have broken dormancy as well as trees that I have been repotted. My approach has been to put the most sensitive trees in the back of my pickup and back them out of the garage each morning once temps come up above freezing the leave the out all day and back into the garage at sundown. However I can’t keep doing that forever so a greenhouse seems to be the best option to protect the trees until spring arrives for sure. I doubt that Charlottesville is much different from us down here.

You have accurately described the experience up here, yes. I just checked overnight for the next couple nights and temps will hit 20s. It makes me uneasy to think I can leave them out during the day of 60s and 70 and then overnight in the low 30s and 20s.

Hartinez · Feb 5, 2024

Bonsai Forest said:
The reason I brought them into the unheated garage was the day of 70F and week of high 60s. I thought I understood it as dangerous to health/life to go from 30s to Summer temps then back to 30s overnight. They’ve been consistently at around 40ish thus far since the sudden heat. Perhaps I misunderstood how they’re supposed to transition from winter to spring.

I’m happy to bring them and leave them out if it’s safe and overnight frost or freeze is not a risk while days are warm.

You’re not wrong. But something important to remember with how our plants transition through the seasons is that temperature is not the only factor that decides when it’s time for a tree to wake up. It’s also day length that helps determine wether the tree decides its time or not. If it’s 70 degrees but the suns angle and time in the sky is still the same as the week prior, I would think the tree knows good and well that the high temps are fools gold.

Hartinez · Feb 5, 2024

Bonsai Forest said:
You have accurately described the experience up here, yes. I just checked overnight for the next couple nights and temps will hit 20s. It makes me uneasy to think I can leave them out during the day of 60s and 70 and then overnight in the low 30s and 20s.

During the spring when we routinely get up to the 60s and 70s but still drop below freezing I leave my conifers out and just leave them on the ground. Especially if I haven’t repotted them. Also because of this, I like to delay repotting of my conifers. Deciduous I base almost solely on bud and leaf break, while most conifers I delay till after average last frost and even till end of may.

Deep Sea Diver · Feb 5, 2024

Ours are generally kept outside.

There is one important exception. If a conifer or other tree has been recently been worked on substantially, wiring, big bends… the tree either goes in the cold frame if freezing temperatures are moderate… or If hard freezes into the cold greenhouse. We have four presently residing in one or another location.

cheers
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When To Remove Conifers/Evergreens from Unheated Garage as Winter Closes (?)

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