Overwintering - A Discussion

[Deep Sea Diver]

Of course, all of us would love to have the resources to utilize the “Gold Standard.” For most of us, that is not an option due to financial and/or space constraints.

If I had a greenhouse like Mirai, I’d put most/all of my trees in there!

Fair point, one has to work with what they have available.

Yet it seems important imho to have a wintering over technique benchmark for folks in colder areas to think about each winter while making preparations.

More importantly the concept might provoke folks to think about working to improve their wintering over processes each year. Just like one works each year to improve their processes and timing on working each of their trees. Especially on wintering over as the trees reach the refinement phase.

(Of course at some point one might reach what they consider their personal gold standard for their microclimate, space and or financial situation.)

Anyways, just a thought. Each year we have set aside a bit more financial resources to devote to our wintering over processes. This has resulted in better storage, more confidence in the wintering over process and trees that are ready to work on come spring.

cheers
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[IzzyG]

Decent summary, although I got somewhat lost in #1 and 2 each of which are complex subjects. However it seems you are pretty much on track.

Methods: Comparing professionals is interesting, yet may not be of much value unless one knows the species kept, age and work/goals for each tree and these and their microclimate matches one’s own.

Most professionals generally work with large specimens more aged to get the best return on their money. In contrast many bonsai hobbyists have a plethora of specimens, generally much smaller and younger.

I believe over the years Ryan Neal has become more and more a member of the, “I’d rather be safe then sorry camp“ vs the “My trees survived the winter“ camp. Money talks.

For an example of a place that is perhaps the gold standard on wintering over trees safely, I do know at PAC Bonsai Museum the trees in display are in open front boxes, that are closed/heated during the winter if temperatures are forecast to dip below freezing for longer then overnight, or if drastic dips below freezing are forecast. All the rest of the trees are kept in inside storage… cold or hothouse. The Curator was the assistant at the National, wonder it they do the same there? Anyone privy to this information?

Timing: In our case, everything gets an appropriate winter home pretty much at the same time, mainly as we don’t like running forth hither and yon with trees in freezing weather. Things are more susceptible to damage, being brittle and freezing hands and ground make for accidents. Been there, done that!

cheers
DSD sends

Points 1 and 2 were basically covering the initial idea; factors that dictate over wintering decisions. Ability to maintain temperature(within the desired range) with the least amount of temperature fluctuations while still giving wind protection is one of the main factors. Some of the discussions on other threads touched on this(and other discussions elsewhere) and hence why I listed it as a factor. For example the decision of a greenhouse might allow one to protect against harsh winter winds but unless properly kitted out, the temperature fluctuations are a major deterrent. Same as point 2; just another factor in our over wintering decisions of what options to use, how quickly to provide protection, etc. Definitely varied and complex but depending on where one lands on the spectrum of these variables, it starts to lead towards an over wintering decision.

I actually believe that keeping the trees cold enough is going to be a bigger challenge when we get random warm streaks here of 50-70 out of nowhere during winter.

 

[Deep Sea Diver]

Sounds like you are developing some interesting ideas.

My position on key factors for overwintering, as it applies to all temperate trees, with an azalea focus, are outlined in this resource I posted recently.

Please me know if you think there are additional factors to be considered. After all, it is only ver 1.01!

cheers
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[Shogun610]

I’m improvising, temperature around here is going to 19 tonight I did bring my persimmon , recently wired and money trees into the unheated garage for the night , most of my stuff is behind the house near the steps , enclosed with wire fencing . It also protects against the wind. Other stuff is grouped together on the ground ,luckily I’m working with all hardy trees(except 2 persimmon) well into zone 5 , I’m in 6b. Dormancy spray is also key with storing everything so close .. and keeping critters out . Tomorrow I’m raking leaves to put around all the trees. Long term I want to atleast lay some gravel on the ground but may not be necessary

 

[Deep Sea Diver]

Nice!

Bedding down final steps here. Tomorrow is first round for copper spray and top mulching. All ready for a long winters night.

Just in time for an awesome dive trip to the Philippines after Thanksgiving!



cheers
DSD sends

 

[yashu]

I

Nice!

Bedding down final steps here. Tomorrow is first round for copper spray and top mulching. All ready for a long winters night.

Just in time for an awesome dive trip to the Philippines after Thanksgiving!

View attachment 463597

cheers
DSD sends

Hey DSD, do you copper spray your azaleas?

 

[sorce]

Stick em on the ground.

They don't die and you don't have to think about them for 4 months.

Time and headache fully saved.

Sorce

 

[Deep Sea Diver]

Wow @sorce ! I admire your Darwinistic approach to wintering over!

But on the ground? What ever happened your ole "Just stick them out on the balcony technique?"

Humbly, yet regretfully, not my style.

Hey DSD, do you copper spray your azaleas?

Yes I do. Usually 1/2 strength in the greenhouse (Also spray the leaves periodically with H2O2 solution) and full bore in the cold frame.

jfi: It really helped me to knock down the fungus by stripping all the inner branch leaves while leaving the 6-8 leaves on the terminal and side rosettes on my azaleas. They'll fall off eventually and are fungus traps either on the trees or on the ground underneath. Learned this lesson the hard way a couple years back. Took me 1.5 days in the winter to police all the bonsai, pre bonsai, whips and surface of the media of all the fungus ridden leaves.

Doesn't help with the @!!%**^!! rabbits though!

Cheers
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[dbonsaiw]

and top mulching.

Just want to make sure I understand - You will be placing mulch on top of the pots (not just around)? I was debating covering my mulch pile with more mulch to cover the bonsai soil itself. Thoughts?

 

[Cajunrider]

Right now it is pretty simple. I put all my tender trees that are suitable for the grow zone in a big grow box and mulch around the bottom and a thin layer on top to protect the young roots. All my tropical trees are under the overhang for protection from frost. On very low temp days, I will provide some heat to keep them from freezing.

When I move up north I will have to up my game. I will refer back to this thread for more information when the time comes.

 

[rockm]

Just want to make sure I understand - You will be placing mulch on top of the pots (not just around)? I was debating covering my mulch pile with more mulch to cover the bonsai soil itself. Thoughts?

I mulch over the top of the pot at least two inches. That is important, as the mulch traps heat and prevents moisture loss from the soil surface. Not mulching the surface exposes top roots to the worst cold and allows winter dry air to dry soil out.

 

[hemmy]

Doesn't help with the @!!%**^!! rabbits though!

I don’t understand how anyone can keep trees on the ground without a fence for the the rabbits. This summer was my first experience with them and they tasted several trunks before I got trees up on benches.

 

[Cajunrider]

I don’t understand how anyone can keep trees on the ground without a fence for the the rabbits. This summer was my first experience with them and they tasted several trunks before I got trees up on benches.

My experience with wabbits have not been fun either.

 

[rockm]

I don’t understand how anyone can keep trees on the ground without a fence for the the rabbits. This summer was my first experience with them and they tasted several trunks before I got trees up on benches.

I've been overwintering trees on the ground for two decades now. Have never had an issue with rabbits. We have a large population of foxes, coyotes, hawks and owls who keep the rabbit population pretty thin. I haven't really even seen a rabbit in the last five years. I have had issues with chipmunks though. They will bite trunks and chew stuff. THey're a pain in the ass, but really a minor annoyance since I have larger trees that aren't harmed as much as smaller trees might be.

 

[Deep Sea Diver]

Just want to make sure I understand - You will be placing mulch on top of the pots (not just around)? I was debating covering my mulch pile with more mulch to cover the bonsai soil itself. Thoughts?

That is correct, we use small bark nuggets on top of the media. For big jobs I usually shake the bag repeatedly, so all the dust settles to the bottom of the bag. For fine jobs I sift it.

Also water the bonsai first, then wet the media. Strangely enough the bark can get wet in and the media could be dry if this isn’t done.

I mulch over the top of the pot at least two inches. That is important, as the mulch traps heat and prevents moisture loss from the soil surface. Not mulching the surface exposes top roots to the worst cold and allows winter dry air to dry soil out.

Yes. 2” seems about the sweet spot. Anymore might be cumbersome.

During the winter media temperature studies last year covering the media didn’t reveal itself as preventing a lower temperature over time, for longer term events. But showed as a moderation of the time it takes to achieve a low or high temperature change.

For short term freeze thaw events (24-48 hrs) the temperature data revealed a more marked moderation of the high and low temperatures the media achieved. Especially during morning freeze daytime thaws. The amount of moderation was, as one would expect, more marked during the warming part of the cycle.

Bark wetness: I didn’t measure this directly as it’s hard to do in the PacNW (too persistently wet). Yet it seemed to me if the media was dry vs wet more rapid changes occurred. Likely a good test for someone in a different environment.

I did test bonsai with overhead protection (large rhododendron canopy 4’ overhead and without. This form of protection moderated rapid temperature changes. Again more marked for short term changes, but confirms the prevailing wisdom.

I don’t understand how anyone can keep trees on the ground without a fence for the the rabbits. This summer was my first experience with them and they tasted several trunks before I got trees up on benches.

A couple resident of rabbits here every year. Especially like small trees….maples, azaleas, hornbeams etc, but rarely conifers. There are certain areas in the yard they don’t like and others they do. Mostly those on the edge of the yard.

Quick rabbit fence made out of netting (poly deer netting?). We stick tomato trellises and pole around the periphery and roll the netting around them, tying the netting off against the ground and up to 30” high. Stake down lower edges as needed. Double up as needed. Netting is cheap. (7’x100’ = 21.00 this year)

Big trees on outside, smaller ones inside.

cheers
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[Wood]

...The Curator was the assistant at the National, wonder it they do the same there? Anyone privy to this information?...

Volunteer at the NBPM here for about a year. The Chinese Collection pavilion has a roof put on it and functions as a cold frame for trees on display, and is kept open to the public. There's a behind-the-scenes greenhouse that's kept about 50 degrees, I think, for sensitive species and anything that's been recently worked on. There is an outdoors grow-out area, but I think they try to minimize the number of trees there

 

[rockm]

Volunteer at the NBPM here for about a year. The Chinese Collection pavilion has a roof put on it and functions as a cold frame for trees on display, and is kept open to the public. There's a behind-the-scenes greenhouse that's kept about 50 degrees, I think, for sensitive species and anything that's been recently worked on. There is an outdoors grow-out area, but I think they try to minimize the number of trees there

Yep. The National Bonsai and Penjing Museum has a number of options to store trees for the winter. I took a tour a while ago of the entire facility. The Chinese pavilion is one place trees are overwintered. It is used for most of the trees on display. It has solid walls and a grid system roof that allows panels to be moved around to cover the trees if I remember. There is also a smaller (although smaller is relative, as it is pretty large), dedicated space "off stage" for trees. It is minimally heated, but has benches etc. It was built with the specified intention of keeping trees that weren't being displayed, recovery, overwintering, etc. Open-faced boxes on display benches aren't adequate protection here.

 

[WNC Bonsai]

In the past I have bunched mine together in a windbreak with mulching and they did fine. However lately fungal issues have been more and more of a problem each year. I tend to feel it is related to the mulching so this year I decided to bunch half on the north side of my porch and see how they do next summer. I used to do it this way until the mulching gods sprang up so its back to my old ways. Here in zone 7a we never get long periods of freezing temps, just cold outbreaks and it is almost impossible to avoid freeze thaw cycles even with mulching. We also get regular enough rains to keep the soil moist and I rarely have to do any watering. Hopefully this and a late winter dose of lime sulfur will help with the fungal issues.

 

[Deep Sea Diver]

. Open-faced boxes on display benches aren't adequate protection here.

One would think so. Only the most winter hardy trees are displayed in winter at PBM. The only tree I recall offhand that isn’t boxed in a heated cube is the subalpine fir, and of course the enormous Domoto Maple.



This the box set up.


If one looks on the lower right side of this photo, the front covers are visible.


cheers
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[Cmd5235]

Due to my ongoing battle with various small animals destroying my trees, I'm trying something new this year. I replaced the substrate in my grow beds with 2 inches of gravel, hopefully to inhibit mice making nests under my pots, from which they launch their tree-eating raids. I'm spacing out my trees, but applying chopped leaves to the tops of the pots only, just to hold in a bit of moisture, with traps placed between pots. These are my bonsai and pre-bonsai in shallow Anderson flats, so the pot depth shouldn't be deep enough to attract nest-making mice.

My one bench that was hit hardest has all of my remaining pre-bonsai, most of which are in 1, 3, and 5-gallon pots. I'm keeping these on low benches as long as possible. These are the trees where the mice chewed holes in the sides of the pots and ate the roots from the bottom up. I'm hoping that by keeping them elevated slightly, it will reduce their attractiveness for a nest. Granted, I may lose a few trees in the process due to the cold, but I fear I will lose them either way.

As a side note, the kill count now is 23 mice, 3 voles, and 1 massive rat, all within the last month or so. It seems the squirrels have found how to disarm my outdoor snap traps without being caught, but I haven't seen chew damage in over a week, a first for me.