Curing the bonsai trots

[WNC Bonsai]

Ok, this stuff with having to move all these trees that have leafed out early, in and out of the garage, is getting a little old. So what is the cure for this? In addition to those that have popped buds, I also have done a large amount of repotting this spring and I don’t want to leave them out and get those newly forming roots killed. Last night we hit 25F here so I put everyone to bed in the garage, even my big Austrian pine got wheeled in since it was root pruned and put into a grow box recently.

So first, let’s talk about which trees can actually take a mild freeze even after they have started budding out. I’m thinking conifers in general as long as they were not repotted. However what about bald cypress, how much can they take? All of mine have some amount of new foliage popping out.

Another one would be natives like hornbeam. How much can they take? Will they be OK as long as the roots don’t refreeze?

I’m going to assume that anything that was repotted needs protection. Does that protection mean no exposures to temps below 32F?

Finally what can we do to protect the trees short of hauling them in and out of the garage, etc? I have been looking at small temporary greenhouses for winter protection, but even those would need some amount of heat, right? I see some commercial operations with polytunnels to protect their trees, would that work as longs the ends could be closed off at night? I also have read of folks who winter their trees under their benches with just a piece of poly draped over them to form a mini greenhouse. The problem I see with these mini greenhouse “solutions” is thst they might have a tendency to overheat easily on warm sunny days and freeze on really cold nights.

I have even considered digging a root cellar in the bank behind the house and using it like @Leo in N E Illinois does with his well house. The earth should serve as good insulation and I could easily use 2” foamboard to insulate the roof. Seems like size would be the issue on that one. Ok, that’s my question, go at it with your experiences.

 

[Forsoothe!]

Nothing beats a pit, but that's a lot of commitment, money, time, & land. Most hardy trees are fine outdoors, but there's lots of arguing whether they should be in shade/protected or like mine in full sun. In full sun, on the ground, mulched over the rim of the pot, they stay the temperature of the ground, approximately, so they don't get ahead of themselves. When they leaf out there's no problem with sunburn, unlike trees in shade or buildings where the leaves get fried if you don't re-introduce them to the sun gently. I don't put them up on the bench until temps stabilize in late April or May ~1st~, and that does slow me down, but that's one trade-off. Another is ice damage. Not from ice storms which are unfriendly enough, but melting heavy snow is the worst. The problem being that a deep block of snow can melt from the sides, like in-between trees where the snow doesn't bridge as deeply, then when just a few lighter branches are left holding up a block of snow has has become more dense due to melting, freezing overnight, melting, freezing, the block of what's now mostly ice is heavier than the branches can hold cracking or outright breaking strategic branches. Proving once again, a pit and the accompanying mice are easier to deal with, sort of, but a pit big enough is a big deal to make. People with hilly land have an advantage. An end-loader can make a gouge in a hill and stack that soil to make the outside wall. For us on city lots, there isn't really enough room to devote to a pit. Nothing is easy.

I used to have an above ground enclosure for Carolinian trees (zone 7 & ^) but now I keep those in a greenhouse on the floor under the tables because I don't have a cement pad to put that structure on at this house. It was in a southwestern facing inside corner where the brick walls gained heat in the daytime and re-radiated it back at night modifying the depth of cold overnight much like a rock garden/mountainside works. The whole thing was in flat panels that spent the summer stored in my garage on a high shelf. I would probably still have it if that area was paved like the patio of my old house, but without a dead-flat surface to seal against, the system doesn't work.

 

[Anthony]

Look up the older Japanese practices, as Forsothe suggested.
Try to stay with natives or trees rated for your zone.

Down here trees from zone 7 and lower, that control their
dormancy requirements are grown in dappled light or bright
light ------ example the zone 7 Chinese hedge - The deciduous
Sageretia or the zone 9 Celts l [ uses a fridge at 9 to 10 deg.C ]
for two months ]
Good Day
Anthony

 

[Dav4]

The main keys are knowing your specific micro-climate and keeping your trees as cold/dormant as possible as late into the spring as possible. Once a tree starts to move in the late winter/spring, all bets are off as far as cold hardiness. In my yard, any tree that gets re-potted will receive some kind of protection if freezing weather is approaching, but that depends on the species in question AND the size of the pot. My nicest, smaller and more manageable trees will always get moved into the garage if I'm able, but the bigger and heavier ones will likely have stay out. My very cold hardy trees- mainly junipers- will get placed on the ground under the deck, maybe with a mulching of leaves. Same thing with the deciduous trees in large mica pots or wooden boxes, but they will get a heavier layer of mulch. Unless you have identifiable leaf edges, your goal is really to keep the soil in the pot from a hard freeze. There definitely is an inherent risk to leaving trees out in the freezing temps, but I have had many trees over the years that have frozen solid post re-pot and haven't lost any save a shohin goji berry which had already experience root trauma earlier in the year... and my bald cypress is too big to move and had buds swelling when it froze solid a few weeks ago- it's fine. As usual, you mileage may vary...

 

[Forsoothe!]

Once a tree starts to move in the late winter/spring, all bets are off as far as cold hardiness.

Yes, winter doesn't kill trees. The false spring kills trees when we have a warm spell too early and then a period cold enough to stop growth. Some won't restart. A late hard frost is another kind of killer. We're better off not having a nice spring, or an early spring. What's nice for people is not so nice for trees.

 

[WNC Bonsai]

@Dav4 your comment about moving trees in as long as you are able is sort of what got me going on this. At 67 years old and with a bad back I am starting to look enviously at shohin as one option for the future (already registered for the Shohin Show in June in Kanapolis). I have a lot of trees transitioning from nursery pots to bonsai that are in grow boxes etc. and moving those around is a pain (literally). I am hoping that once I get that accomplished I can leave them outside all the time without worry. It is the tridents and J maps that concern me most. I also have a penchant for forests which also tend to be a little big and heavy. Plastic pots help with the weight on those. The other problem is I am running out of room in the garage and it stays too warm in there anyway. So it has to be either the temp greenhouse or the root cellar approach. I am just wondering whether in zone 7 that will keep these trees dormant long enough. While it may work in Michigan and N. Ill and other places north of the artcic circle I am not sure about it down here. Maybe I could combine warming matts with the temp greenhouse.

 

[Dav4]

I keep everything outside (except my olives... which honestly still spent most of this past winter outside). The deciduous trees are on the ground under the deck and covered in leaves, or under benches and mulched. The evergreens stay on the benches (in the sun) for most of the winter but get put on the ground for most of January as needed due to deeper cold. Evergreens are tough and can typically be re-potted later then D trees and can also tolerate more cold post re-pot. Even though having a cold greenhouse to protect recently re-potted trees would be fantastic, it isn't happening for me on the property I currently live on but might be something you could benefit from.

 

[Leo in N E Illinois]

I know a lot about wintering trees in zone 5b, but I think the ''rules'' change for zone 7.

1.) Repotted trees, trees that were repotted in autumn, winter or in the last few weeks - all should be stored so that the pot with the roots does not freeze. Frost on the branches, especially if they are not growing is not usually an issue, it is the roots. These are trees that need a spot like a well house, root cellar, or other area with controlled temperature.

2.) Natives, to your immediate area (same elevation, say within 100 miles, or 190 kilometers. These should be wintered outdoors, pots set on the ground, and a mulch, or windbreak applied if needed. These trees should be able to handle late frosts. They won't start growing until it is safe. Introduced species not native to your area, might sprout too early, but if they are used as regular parts of local landscape plantings they likely will bounce back from the late frosts. So again, these trees should not need to be stored inside anywhere. Just pots on the ground should do it. There is some debate about whether pots on the ground need to be set in a spot in the shade, protected from sun, especially late winter sun, or not. One of the Mirai videos says no. My experience say yes for some trees, no for others. I usually set most of mine in shade. A few like Amelanchier are just left where they grow in the sun. My crab apples also spend winter on the ground (these are larger pots, anderson flats and grow out boxes. My shohin apples are inside mostly because they would get lost. All my junipers are just set on the ground outside.

3.) Natives to areas significantly colder than your local area. These I tend to leave either on the bench, like my eastern hemlock, Tsuga canadensis, and jack pines, Pinus banksiana. These were left on the benches. We had -23 F for a night or two, (roughly -31 C ) So far they seem fine. Previous years they pulled through slightly milder weather still sitting on top of benches. So the gymnastics that I used to take to shelter every damn tree are clearly not needed.

4.) There are some species by species exceptions. For example. Ginkgo - no matter where, I must winter ginkgo in the well house with more tender & sub-tropical trees. Any ginkgo left on the ground, or on the bench will die. Even though Ginkgo is a common landscape tree in my area. Go figure? And the reverse situation. I happen to have a Taxus floridus - the Florida yew. It got forgotten one year, and now spends every winter just set on the ground. That's right, it survives zone 5b winters even though it is native to zone 8. It is only found in a handful of locations in northern Florida. Looks like an ordinary Taxus, nothing special,, not worth seeking out, I just happened to have one. So species by species you might find exceptions.

5. ) My tender trees, from zones 6 and warmer, are all in the well house. Fortunately, even though we have had several daytime highs in the 50's and 60's F, and the well house, being below grade has stayed cool. It is now about 45 F. There is a little evidence of flowering quince, and other trees starting to wake up, but they are not moving yet. So I have left everything in the well house, even though the next 7 days are forecasted to be above freezing, day and night. This warm week is supposed to be followed by a freeze, I'll wait until after the freeze to pull plants out of the well house. Satsuki azalea, JBP, bamboo, persimmon, and others are the species in the well house. Key is, I keep the door closed, so it stays cool, and don't pull out anything early, unless I see etiolated (elongated and pale) foliage growing.

 

[WNC Bonsai]

Thanks @Leo in N E Illinois , I knew I could count on you for a comprehensive response. I am surprised to hear that your well house temp has come up to 45F. Is the above ground portion insulated? I have a bank out back that I could dig into to create an insulated root cellar but I am afraid it would heat up mid-winter when we hit daytime temps in the 60s for a week or two and I’d be right back where I started. I think I’ll start investigating the idea of the poly hoop house as a potential area where I can stash the sensitives and those that wake up too early. I have a flat spot behind my wife’s pottery shed so I could can even tap into the electrical outlets if I need supplemental heat. I’ll abe to see what other folks innthis area are doing too.

 

[Leo in N E Illinois]

I think the take home I'd like others to take is:

Try to set up your winter storage to stay as cool or cold as possible as long as possible. If you can keep your winter storage cool, below 40 F, right up to the time of average last frost date for your location, then you do not have to invest in greenhouses, hoop houses, and other structures. Greenhouses and hoop houses all have the flaw that they can get very hot and very dry quickly on a sunny day. Many a tree has been killed by such a structure.

Idea - for those wintering in garages - a garage can heat up during the day. Try what a carnivorous plant grower in my area does. Styrofoam coolers, the cheap styrofoam beer coolers. All trees get set in a cooler. In each cooler 3/4 full with water 2 liter bottle of water. The water is to provide thermal mass, help keep things frozen if they freeze, and help keep cold if it gets warm. All coolers are taped shut, but no effort made to make totally air tight. The coolers are all set on the floor of the garage. This way warmer zone plants are kept cold enough that they don't start to grow before freeze danger has passed. The key principal is to protect your tree from the high temps of the mid-winter thaws, and early spring warm weeks before last frost. This method works.

The styrofoam cooler, with a water bottle for thermal mass also works for those that have to winter trees on balconies and patios, because they are in an urban situation.

The second idea is to really focus on trees that are native to your area or areas that are colder than your area. Nobody in North America should ever have to put a mugo pine in a heated structure for the winter. Out of the wind, yes, out of the cold, never. They are hardy into zone 3, so should not need temperature protection. Look north my friends and embrace the botanical diversity of the northern climates. Amelanchier are incredibly hardy, lovely blooms before the leaves. Ideal for shohin and medium sizes. Explore the possibilities.

I think too many of us protect trees from cold that do not need protection. But, like with my ginkgo example, there are exceptions that vary from location to location. You will have to experiment. I leave my larger crab apples outside all winter in zone 5b, how many of you in warmer areas have your crab apples in some sort of warm shelter? By doing so you have created problems for yourselves. I absolutely hate the ''in and out'' dance, and have lost a few trees experimenting with how to avoid it. I also have limited room in my near ideal well house, so I try to keep the number of trees I have to move around to a minimum.

My evergreen azaleas, mostly Satsuki types, are all in the well house, dark and cool, and seem fine for the rest. I won't bring them out until frost danger is passed. They do fine that way, as does pomegranate. But again the reminder, it works only if the storage area stays cold. One BNut, who I haven't heard his progress on this was wiring a thermostat into an air conditioner that would allow him to set it to 36 F. He planned to install the air conditioner into his winter storage shed, to keep the shed cool the last couple weeks before it is safe to put trees outside. An air conditioner and thermostat is cheaper than putting in a hoop house or greenhouse.

Well those are my further thoughts.

 

[Shibui]

I think the solution is real easy. Move to a more reasonable climate!
No need to move trees or elaborate overwintering over this side. Excepting tropical, they all stay put on the benches all year.

 

[Anthony]

Well Leo,

if technology helps. The Celtis l, just came out of the fridge after
2 months [ since 1980 doing this ] and the measured temperature
was 6 deg.C for the start and as the covered patio heated up
the last two weeks were 8 to 9 deg.c.

Trees were watered weekly, and plastic bags tied around the pots.

Leaves fell off after 2 weeks of cold.

Now we wait a week or two for buds.

Old fridge set on 1 or low.
Good Day
Anthony

Old idea adopted from the Canadians who grow Maples from zone 7.

 

[sorce]

Everything can work...OR NOT..
Everything has worked....AND HASN'T.

There is only 2 good ways to go about it,(unless you need VC protection but that doesnt change much)

1. Fully Regulated Working Climate Control.
(See JudyB setup)

2. On the Ground Right Where they Live.

As always....it is about reducing confusion.

A tree that spent the entire year reading light in its position isn't going to correctly read the light in a new position.

Remember trees don't move.

It's like you navigating by shadows alone...
But in 2 different seasons.
You can't get to the same place!

Your tree is equally confused. Hence early or late budding, regardless of what we think they think the light and temerapture is, we fucking changed it on them! We shouldn't!

(Don't mean you you.) (I mean you!)

I've been able to survey everything well now this year.....
My little English box that is in a 3x1/2in pot with as much soil as a mediocre Cowboy Chew lost some leaves.....but buds are intact and no design lost.

My twiggyest twigs on the @VAFisher winged elm are fine.

-23F we hit.

So much Bullshit surrounding winter/wintering.

Sorce

 

[VAFisher]

I winter my deciduous in the garage and they wake up early. So I do a fair amount of moving them in and out. They inevitably spend time in the garage after they leaf out because it's too cold to move them out at 7am when I leave. I worry that they'll get leggy because of that but it hasn't been too bad. That's the bad. The good is that I can keep a close eye on them all winter because I walk through the garage at least twice a day. And I haven't lost a tree to winter in about 4 years. So I figure if it ain't broke, don't fix it

 

[VAFisher]

Everything can work...OR NOT..
Everything has worked....AND HASN'T.

There is only 2 good ways to go about it,(unless you need VC protection but that doesnt change much)

1. Fully Regulated Working Climate Control.
(See JudyB setup)

2. On the Ground Right Where they Live.

As always....it is about reducing confusion.

A tree that spent the entire year reading light in its position isn't going to correctly read the light in a new position.

Remember trees don't move.

It's like you navigating by shadows alone...
But in 2 different seasons.
You can't get to the same place!

Your tree is equally confused. Hence early or late budding, regardless of what we think they think the light and temerapture is, we fucking changed it on them! We shouldn't!

(Don't mean you you.) (I mean you!)

I've been able to survey everything well now this year.....
My little English box that is in a 3x1/2in pot with as much soil as a mediocre Cowboy Chew lost some leaves.....but buds are intact and no design lost.

My twiggyest twigs on the @VAFisher winged elm are fine.

-23F we hit.

So much Bullshit surrounding winter/wintering.

Sorce

Glad to hear that winged elm is alive and kickin. I'm growing trunks out on the 2 brothers to yours. And I put the parent tree in a bonsai pot this year. I think it's 3 years from yanking the seedling out of my flower bed.

 

[0soyoung]

One possible answer is to keep your trees warmer after leaf drop or give them some warm periods in storage.

Trees don't just get cold and then break bud the first time the temperature rises above 40F. A number of hours below 40F must be accumulated before warming will cause bud break. This chilling time is something like 1000 hours for many temperate species. It varies across species and even cultivars.

In a 'really cold climate' temperatures fall and stay below 40F day and night. Here it would only take about 6 weeks to accumulate the chilling hours. Buds will then break the first time it is warm and you've got the 'false spring' problem. In a cool climate like mine, it is below 40F only overnight (call it 8 hours a day), so it takes three times longer, 18 weeks, to accumulate the chilling hours.

 

[leatherback]

I am not in such a cold zone; It is very cold here if we hit 0F in a winter. We do get loads of irregular frosts through. We hit the low 70-ies a week or so ago, and the temps dropped to night time frost with all deciduous growing. I lost just the tips of a few leaves.

MOST plants local to your zone will know how to deal with frost, or can regrow if they loose that years' foliage.

Exception repotted olives, pomegranates and mumes. They went into the greenhouse for the night. But my maples, junipers, pine, yews, beech, larch, lonicera stay outside.