Author Topic: Winter Hardening?  (Read 3499 times)

Josh

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Winter Hardening?
« on: October 07, 2012, 09:51 PM »
All,

I live in zone 4b. 

I keep my bonsai in a heated poly tunnel during the winter, and the trees have done quite well, min temps kept in the 40s.  About this time, I put the trees down for the winter in the poly tunnel, yet I find that the deciduous trees have not all dropped their leaves. 

I would like to consider leaving them out longer, so they drop their leaves (cuts down on the mess), and I could give them a dormant spray.  At this time of year, night time lows are bouncing around, but may go below 30, with a hard freeze.

I think the evergreens will be fine.  But am I taking a risk with the deciduous trees?   I have japanese maple, tridents, chinese elm (I worry about these the most), hornbeam, beech, crabs, plum, hawthorne.  Is it silly to try to harden these trees, just to cut down on greenhouse mess and dormant spray?

Thanks, Josh
 

Jay

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Re: Winter Hardening?
« Reply #1 on: October 08, 2012, 07:35 AM »
Josh, I am in a similar situation. I try and give my trees as much outdoor time as possible. I enjoy the fall color display and am willing to tolerate the "two step" of bring them in at cold nights and out again in the AM .  But, when I feel it time, I take a few hours and cut off the leaves that remain, then place them in my cold room for the winter.

This works for me....

Jay
 

Owen Reich

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Re: Winter Hardening?
« Reply #2 on: October 08, 2012, 07:58 AM »
We cut leaves on many deciduous trees here in Osaka (and we have a lot of them too).  If they are turning it is no big deal to remove them.  You will lose a little energy the tree is in the process of recycling, but nothing serious.

While on the subject, cutting leaves off strong branches of deciduous trees just before the leaves start to turn can help balance spring flushes.  This is especially true on one of my favorites Prunus mume.  Our Fall seems really early this year.  Saw Fall color on an Acer palmatum 3 weeks ago on my last day off while in the mountains north of Kyoto. 
 

Josh

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Re: Winter Hardening?
« Reply #3 on: October 14, 2012, 05:31 PM »
Thanks for the replies...

This year i started using akadama, pumice, lava soil, in the general 'Boon mix' tradition.  Me thinks the akadama is getting a bit soft with the recent freeze/thaw. Any thoughts from the peanut gallery?
 

cbobgo

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Re: Winter Hardening?
« Reply #4 on: October 14, 2012, 05:52 PM »
According to Brent's species info at evergreengardenworks.com, all of those trees can survive dips below 0.  It's generally repeated freezes and thaws, and late spring freezes that do the most damage.  They should all be able to tolerate fall freezes OK.

- bob
 

John Kirby

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Re: Winter Hardening?
« Reply #5 on: October 14, 2012, 09:24 PM »
Bob, Has Brent ever had his trees survive below zero in a bonsai pot? John
 

Josh

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Re: Winter Hardening?
« Reply #6 on: October 15, 2012, 10:33 AM »
Although I live in 4b, I wish to give the trees a bit of TLC.  I don't want to take the winter hardening too far.  It would be idea if I could expose the trees to a couple hard frosts, let them defoiliate, and use dormant spray before they go into poly tunnel for the winter. So, I really don't want 0 degree exposure, particularly maples, tridents, etc.

John Kirby, as a SOB (I use that term in the positive), have you experienced trouble with akadama breakdown with freezing?  I potted up many trees this year with my own Boon mix (after an intensive) using AA akadama, pumice and lava.  The akadama was intact until this fall, when I started to observe breakdown after some frosts.  Pots still drain well. I recognize akadama will break down, but this seems a bit fast.  In future, look for different akadama, substitute this component for something stable with freezing (Turface), move to LA?

Thanks, Josh
 

cbobgo

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Re: Winter Hardening?
« Reply #7 on: October 15, 2012, 01:36 PM »
John, I don't think it gets below zero where Brent lives.

- bob
 

dre

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Re: Winter Hardening?
« Reply #8 on: October 15, 2012, 03:24 PM »
for this reason i grow only thing that can handle the cold with no re special protection. like i leave all my larches on the bench all year round winter and all one of my big yamadori yew stays out during the winter everything else from jbp to junipers and potted yews go in the unheated garage
 

coh

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Re: Winter Hardening?
« Reply #9 on: October 15, 2012, 05:26 PM »
All,

I live in zone 4b. 

I keep my bonsai in a heated poly tunnel during the winter, and the trees have done quite well, min temps kept in the 40s.  About this time, I put the trees down for the winter in the poly tunnel, yet I find that the deciduous trees have not all dropped their leaves. 


You keep your trees in the 40s all winter?  I know everyone has their own way of doing things, but that just seems unnecessary. Here in Rochester (zone 6a) Bill Valavanis keeps the vast majority of his trees in a garage heated to about 28 F during the winter. I would think in zone 4b you'd want to take advantage of the cold as much as possible to keep the trees dormant. Please don't take this as a criticism, I'm just curious why you keep them that warm?

Chris
 

Josh

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Re: Winter Hardening?
« Reply #10 on: October 15, 2012, 10:41 PM »
Chris,

Thank you for your thoughts...

Regarding over winter temps of roughly 40 degrees, it started where I started in bonsai, Seattle.  All of my trees at the time were local, and stayed outside year round. Occasional frost and snow, but never severe cold.  I moved to the Midwest 13 years ago, and took these northwest native trees with me.  I was concerned (maybe over concerned) that the cold would be too much. At my former house, I had a temp controlled greenhouse, and for the last 3 years a poly tunnel. With the poly tunnel, I have less control of the temps, and have choosen (maybe incorrectly) to keep the trees at temps which approximate the northwest (Seattle).  I may be going too early to the poly tunnel.  As the thread started, I was looking for others' experiences with winter hardening to encourage dormancy. 

At present, trees remain outside, in attemp to get exposure to some frost, and encourage dormancy. Hoping to get leaf drop, but not harm the more tender trees, Japanese and trident maples. 

 

coh

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Re: Winter Hardening?
« Reply #11 on: October 17, 2012, 09:51 PM »
OK, got it! I do think you could keep them colder through the winter, but if it's working...do you have any issues with trees coming out of dormancy too early?

I don't know where you are in the midwest. Here, most keep their trees outside until around or just after Thanksgiving. The Rochester area temperatures are moderated quite a bit by the Great Lakes, especially early in the season. Average daily lows by the end of November are around 30 deg or slightly below. So the trees experience many sub-freezing nights in November, but only rarely do temps get down to 20 or below. At the next club meeting I will ask about how members handle their maples during this time.

Chris
 

Owen Reich

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Re: Winter Hardening?
« Reply #12 on: October 18, 2012, 10:19 AM »
Keeping the trees in a poly tunnel at or just above freezing should be just fine.  Drying winds do a lot of damage to some species.  A dormant oil spray helps the trees too.  Both Acer palmatum and Acer buergerainum are really tough species of trees.  They can take a lot more abuse than you might think.
Seems like a few cold nights to set dormancy and lowering the poly tunnel temp to say 32-35 would work.  40 does seem a bit high and potentially expensive.  I always kept my trees in a poly tunnel that I vented with some slits in the roof (in Nashville) where it gets into the low teens, sometimes zero.
 

Tao

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Re: Winter Hardening?
« Reply #13 on: October 26, 2012, 11:48 AM »
I have a few question after reading the posts since I'm still trying to figure out the whole " don't kill your trees during winter" gig: I've got a juniper and a Trident maple

1. Where can I get this poly tunnel you're talking about? I live in Zone 6 with some characteristics of Zone 5 at times (iowa) so this item may be helpful since I don't have a garage.

2. how often do you still water during the winter, especially in the tunnel?

3. What is the dormancy spray you're talking about and where can I get it? What purpose does it serve?
 

Judy

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Re: Winter Hardening?
« Reply #14 on: October 28, 2012, 08:21 AM »
To find the poly tunnel material, just google "poly greenhouse tunnel", or look at greenhouse suppliers.  You could do the same with a cold frame, just be sure to open it in the warmer days.  And remember that you don't want to site it in a sunny location...

You check your trees to see if they need water just like always - I check mine weekly.  It depends on how warm/cold it is.  Don't water a frozen rootball, but packing snow on them is good if you have snow.

You could get neem oil, it's readily available.  It helps with overwintering pests on your trees.
« Last Edit: October 28, 2012, 08:24 AM by Judy »