Frozen soil.

It has been rather cold the last few days. So I have been moving my bonsai into a shed over night. The shed doesn't let in any light so I have been moving them out during the day. This morning when I got them out I noticed that the soil was frozen. Is this bad? This is my first winter of growing bonsai outside and have read that keeping them in sheds/ garages over night will help protect them from the cold but will keep them cold enough to stay dormant. I have 2 azaleas, 2 acer deshojo, 1 lonicera nitida, and 1 Chinese elm. Can anyone give me advice on the best techniques for over wintering bonsai of these species? I have a relatively small garden which is extremely sheltered from the wind and as I live 100 metres from the sea, temperatures rarely drop below -8 degrees centigrade. Any advice would be much appreciated!

Hello
A sheltered spot is good because freezing winds will dry out a tree quickly, you get frost burn.
You could cover the pots with something when it gets to cold.
The deciduous trees you can leave in the shed.
When a pot is frozen one should be careful not to place it in the sun because a repeated frost and thaw of a rootsystem
is not helpful.
Sunip

You need to know if the tree is suitable to the agricultural zone you live in. If it is then frozen soil is not a problem. As was mentioned before the wind is the problem as the frozen soil does not allow for water to move up the tree when the wind dries the top out. Here in the US where I live I put my trees in a cold dark place (no light is needed since they are dormant). Temps can get to -20F and my trees survive fine.

In many ways frozen soil for deciduous trees is a blessing in disguise as it means you don't have to water your dormant trees and it also insulates the roots as once the soil is frozen its temperature remains at 32F for a time even if the outside air temp may drop into the teens or below.

I have read warnings about Chinese Elm and Trident maples having very fleshy roots with a high water content and that freezing and thawing cycles can sometimes cause the water held in the root system to freeze thereby destroying the root tissue. I have never had this happen to me and I've had Tridents and Chinese Elms both have their soils freeze with no ill effects.

-Jay

drgonzo wrote:In many ways frozen soil for deciduous trees is a blessing in disguise as it means you don't have to water your dormant trees and it also insulates the roots as once the soil is frozen its temperature remains at 32F even if the outside air temp may drop into the teens or below.

I'm not sure if this is a typo...once all the water in the soil is frozen, the temperature of the soil will definitely drop! It won't drop as fast as the air temperature, but if you leave a frozen pot out in, say, 0 F cold long enough, the soil temperature will eventually get down to or near 0 F. It will just take a while.

Chris

i looked on a couple of science sights and ice can continue getting colder down to the maximum of absolute zero (-273 ? i think) Aparrently ice will drop with the ambient temp, otherwise it would all instantly melt the moment the temp rises a little bit.

i dont mind frozen soil with most things - over the last 20 years my chinese elm has always sat outside, uncovered, unprotected, so has my tridents, acers, white pines and most other stuff - i did not protect the satsuki last winter and the first flowers were deformed but the tree was fine. i keep black pines, and trees with black pine roots protected though. This year i have my first cuspidatta japanese yew but i cant fit it in a greenhouse or through a door so the pot is protected with several layers of foam carpet underlay but the foliage is exposed - i believe this is the best combination.

over the years i've concluded ice and frost is fine if the soil is not waterloggged. one year i put the trees in the garage - but they still froze solid in there. i have never had a single tree die in the winter and not break dormancy in spring - the ones that died in the early days were killed while learning about soils, repotting, root pruning etc

You know where that comes from is and old orchard trick I heard during one of my trips to the deep south.

If a freeze is imminent and a crop may be lost (usually its a fruit crop sometimes they do it up north for grapes that are pushing their buds too early) they turn on the irrigation lines and let the water freeze to protect the fruit. There are fruits or buds that can withstand 32F much better then say the teens overnight and this was meant to insulate them..

Might be an 'old wives' (farmers) tale that has stuck in my head.

-Jay

It's not an old wives tale. There are a couple of mechanisms at work. The water releases heat as it freezes, so if it's a borderline freeze (uppers 20s/low 30s) that can help protect the fruit (or flower buds in spring). And if the plants get encased in ice, the ice does act as an insulator...which can work as a shield for a few hours/overnight but if the air stays cold long enough, eventually the cold will penetrate the ice and damage the plant.

I agree with chris also. This will work. Oh and hello to you both hope all is well. Happy holidays.

Neil

Thank you for clarifying that Chris!

One of the issues I run into in my storage area is that my pots rarely freeze as the temps stays nearly steady at 38F so I have to keep a watchful eye on soil moisture and make sure nobody dries out. I lost some collected Beech seedlings due to that last year and have learned my lesson.

-Jay

Yep, I've had that problem in my mudroom (where I keep the less hardy plants) where temps stay between 35-40, especially with evergreens like my camellia. Haven't lost anything but had some close calls...

Nice hat, by the way!

Hey Neil, things are good, just waiting for winter to arrive so I can put the last of my trees away. Still got a few evergreens outside...haven't had a night get below 20 F yet. And almost no snow.

coh wrote:
Nice hat, by the way!

I make my own fun.

@ Neil, good to hear from you man. First Christmas in the new home if memory serves right? Make it a good one!

Best
-Jay

this was meant to insulate them..
might be an 'old wives' (farmers) tale that has stuck in my head.
-Jay[/quote]
Hello,
It is a routine thing here in agriculture but as Chris stated temperatures will get lower in the pot.
I lost some trees due to this.
Hello Marcus, i lost a yew as well due to this as they have very soft watery roots, my yews are in the greenhouse when it gets under a few degrees zero celsius, but then you live almost in the tropics outthere in Cornwall and below temperatures will be rare.
Sunip

drgonzo wrote:

coh wrote:
Nice hat, by the way!

I make my own fun.

@ Neil, good to hear from you man. First Christmas in the new home if memory serves right? Make it a good one!

Best
-Jay

Yes in the new home and thank you for the wishes. Hopefully we will all meet up soon at another event.

Neil

drgonzo wrote:
I have read warnings about Chinese Elm and Trident maples having very fleshy roots with a high water content and that freezing and thawing cycles can sometimes cause the water held in the root system to freeze thereby destroying the root tissue.

Watch out for this on Ginko as well....