Overwintering grow beds

wvbonsai

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I know that trees being developed in the ground for bonsai have greater cold hardiness than those being developed in containers. My question is what about those being developed in grow beds? I have several black pines as well as some japanese and trident maples being grown out in above ground grow beds. Do I need to afford these trees extra winter protection?
 

Tachigi

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JC,
You and I are not that far apart. I'm a zone colder than you and my in ground trees don't "need" extra protection.

However, you will find a quicker response to your tridents in the spring if you hoop them...also it should protect them from critters that nibble ... deer are my biggest problem. Also if you put up a wind barrier on in ground trees you will find that you will have little to no twiggy die back on deciduous trees and on conifers it helps with color. You can wind barrier a couple different ways hay bails, stakes driven into the ground with ground cloth stapled to them ...this is actually an old landscapers trick used to protect low hedges. Really your imagination is the only limit and the size of your grow bed.
 

rockm

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Ditto what Tom said.

Also, the rule of thumb for overwintering--the more soil volume around the roots, the more protection the roots have. That applies from in-ground, bed grown and containerized trees. It doesn't really have anything to do with the roots' proximity to the ground. It has to do with how much soil is around the roots.

For instance, I have a big live oak bonsai in a 15 gallon or so pot. I have another smaller one in a pot that holds maybe 2 gallons. The big tree is entirely winter hardy and has shown little, if any, problems with overwintering in temps down to zero or so in a cold frame. The smaller one, however, consistently dies back to the trunk every year. The difference is simple soil volume--larger mass retains more heat for longer than a smaller mass...

That means, how big are your growing beds? If they hold hundreds of gallons of soil and the trees are in the middle of that mass, you probably don't have to worry.
 

wvbonsai

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Thanks for the input folks! I have attached a couple pics of the grow beds. The first shows some 3 yr old JBP and Shimpaku just planted out this Spring. The other is much deeper and contains some chinese elm, japanese green and trident maples. I will most likely build a wind break as suggested for the JBP because they are in much less soil and I can utilize the existing chain link fence as support to anchor the windbreak.
 

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rockm

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That should work.

I did notice that you've got a plastic container buried halfway up in one of the beds--note that this could be a very real problem, as drainage in the container is probably blocked--which can lead to problems in the wintertime with excessive rain and snow. Root rot is a real possibility with buried pots.
 

wvbonsai

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i just buried tht last week as I noticed that roots were escaping through the bottom. The tree is an eastern white pine I have been toying with. It is planted in 80% Turface 20% pine bark and seems to still drain fine even buried in the grow bed. I have no problem removing it though if you think it would fare better.
 

Tachigi

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I think Marc was referring to the daming effect the ground might have with the pot buried
 

wvbonsai

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Ok I follow now! I'm a bit slow at times! I will pull that pine out of there.
 

rockm

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Tom is correct. Burying a pot shuts up the drain holes, or severely impedes them, even if the soil inside them is pure gravel :) When you bury them and the drain holes get stopped up, you might as well store them at the bottom of a pond 24/7 for four months.

I bury my pots in mulch every winter, but I make sure to place them on a couple of bricks before piling on the mulch. The brick supporting surface between the pot bottom and the soil allows an air space that keeps ground soil and mulch from blocking the drain holes--also make sure pots are relatively level when storing them for the winter. Some pots collect water in corners which can kill roots.
 

wvbonsai

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Tom and Rock thanks loads for the prompt replies and insightful advice!
 
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