Frost in autumn question

[Tieball]

I understand the problem of frost in the spring and resulting damage to some, perhaps most, trees. How about autumn...the time when trees are still in green leaves but are headed for colder temperatures and finally dormancy. My daytimes are in the upper 60 degree range to a possible low 70s. Nights are beginning to drop to the upper 30s. Frost warning are beginning to drift low in Michigan and could be in my vicinity any week or day.

Does frost present a problem at this time of the year?
Is frost at this time of the year more of a natural state of turning the trees to a dormant direction?

 

[Dav4]

Does frost present a problem at this time of the year?
Is frost at this time of the year more of a natural state of turning the trees to a dormant direction?

#1- No.
#2- Yes.

Temperate trees are expecting and ready for light frosts and freezes in early fall, and this cold exposure does, in fact, increase their tolerance for the more extreme cold coming in winter. I really don't worry about temps this time of year.....at all.

 

[october]

Dave gave you great information. Depriving trees of this first couple of frosts can be a bad thing. I assume we are talking about healthy conifers and deciduous (maples etc.), correct?

Rob

 

[GrimLore]

Our tropicals went in last night for the remainder of the winter as evenings are getting rather chilly. All of the rest of the trees can and will stay out again this winter and go through a natural wintering EXCEPT the plants will get buried in pure pine chip to form an insulation barrier that stops the pots and roots from freezing solid. In addition Many trees in pots will get a decent wind barrier after first frost. It depends on species size, pot size, as well as climate. Also if the weather starts to go up and down all of the plants outside full sun will go to a shaded area preventing them from pushing prior to going dormant. There is a LOT of "if" but it is necessary to know each species and YOUR climate and monitor them daily.

Grimmy

 

[Tieball]

Correct...Decidious

Dave gave you great information. Depriving trees of this first couple of frosts can be a bad thing. I assume we are talking about healthy conifers and deciduous (maples etc.), correct?

Rob

American Elm, Hornbeam, Hackberry, Hawthorn mostly. No tropical. Just outdoor hardy trees. Michigan weather trees.

 

[lordy]

I have a different view of what is supposed to happen during the winter. I was taught, and still practice with very good results, to allow the trees to freeze and then mulch the pots/roots. I keep mine in the shade from about Thanksgiving until St. Patrick's day. After they get a good freeze I mulch to insulate so that the roots dont thaw, then refreeze, and so on. Temperate trees can take being frozen but are averse to thawing, freezing, thawing, freezing, and so on. So it is not the freezing that is the problem, it is the freeze-thaw cycle that is the problem.
Frost may do away with this season's foliage, but if the new growth has had time to harden off, next spring should bring a new crop of buds. This is another reason to use 0-10-10 fertilizer from about mid-Sept so that new growth isnt encouraged by Nitrogen in the fert.

 

[Wee]

This is the next thing I have to worry about...Only been doing bonsai for about 3 months...I live in the North Ga area....Freeze/thaw would seem to be unavoidable unless I brought them all inside.....Our winters can go from the teens a couple on nights in a row to 70 4 days later.

Time to do some research.

Brian

 

[Dav4]

Brian, you and I are practically neighbors, so let me tell you what I've learned about the effect of freeze-thaw on my trees during the last 4 winters here in GA..............it's a non issue.......at least for me. My trees 1) are all in 100% inorganic soil, 2) are all hardy to zone 6 or lower, and 3) they all stay on the benches through the winter, except when temps are falling into the teens or lower- they get placed on the ground if temps will fall into the teens for multiple nights in a row. During the winters 3 and 4 years ago, my trees would do the freeze thaw cycle at least 30 times without any issues. If you are worried about it, place the trees in the shade so they'll stay cold, though maybe not "frozen".....but don't worry about "frozen" if your trees are cold hardy.

...and fwiw....I always heavily mulched my pots when I lived in MA. The mulch was NOT to keep the soil/roots from freezing...it was to reduce the extremes of cold AND warmth that the potted root zone might be exposed to during a typical winter. I wanted my pots to freeze without experiencing severe cold, and stay frozen despite the occasional days in January and February where the temps would reach the 60's.....so they'd stay dormant as long as possible.

 

[Wee]

Dave thank you very much for the advice....I was planning on putting them on the ground and mulching over the winter....Sounds like I can just leave them be till the weather gets in the teen's and then only protect them during that time...Now if I can just keep my dog out of them I'll be all set.

How about watering during the winter....?

Brian

 

[GrimLore]

Snow is water... What I am really trying to say is let nature worry about that - honest.

Grimmy

 

[Dav4]

Dave thank you very much for the advice....I was planning on putting them on the ground and mulching over the winter....Sounds like I can just leave them be till the weather gets in the teen's and then only protect them during that time...Now if I can just keep my dog out of them I'll be all set.

How about watering during the winter....?

Brian

Yeah, if forecasted lows are going into the low 20's F, I'll put the smaller pots on the ground even though they probably would be fine. The ground temp is almost always warmer then the air temps and will slow the pot's cooling. A few other things to consider...it takes a long time for the water in bonsai soil to freeze completely, the bigger the pot the longer the time to complete freeze, and until ALL the water in the soil is frozen, the soil temps will stay at or just below 32F, which will not harm the roots of temperate trees. Also, roots have sugars and other molecules dissolved in the sap that acts as antifreeze...the soil in the pot may be completely frozen, but the roots are not and will not freeze unless soil temps fall much below freezing and stay there for a long time.

As far as watering goes, I've found that trees in dormancy really don't use much water, and natural precipitation is more then enough to keep the soil moist. I think I only watered once last November and not again until some time in March.

 

[Tieball]

Winterwater

As far as watering goes, I've found that trees in dormancy really don't use much water, and natural precipitation is more then enough to keep the soil moist. I think I only watered once last November and not again until some time in March.

I have several Celtis Sinensis. They are each in a plastic squat pot -- about 10" in nheight and 15" in diameter. I live in Michigan and winters are cold, generally with a lot of snow cover....mostly from mid December to sometime in March usually. The trees are still growing for trunk development (currently the trunks are 1.5" to 2.25" diameter...still a lot of growth to go).

My questions are around the plastic pots and winter water.

1) Is it better to remove the trees from their pots and put them in the ground with care once all the leaves have fallen and dormancy in settling in?

2) Does it not really make a great difference and the trees can be left in their plastic pots and still planted in the ground for winter? (Ground for me equals a lot of sand...like sand-dune sand)

3) The sand area in the midst of tall pines seldom freezes. The pines tend to shield the wind. The area of planting has a clear overhead for falling snow or rain over the months.

Celtis Sinensis specs say good to 20 degrees F.

Thoughts?

 

[Dav4]

I think everything is fine as far as the pots and location go, except for the winter hardiness of your trees. I can only assume that your location in MI means that you are usda zone 6 or lower...that means winter lows down to -10 f or lower. If your Celtis is only rated to survive cold down to 20 F (zone 9), you would need a location that provides significantly more winter protection then what you've described...like a greenhouse.

edit- I just did a search on C. sinensis and MOST sources rate it to zone 5...if you live in zone 5 or warmer, your plan (putting potted trees into the ground) should work just fine.

 

[Tieball]

I'm a 5B

I just did a search on C. sinensis and MOST sources rate it to zone 5...if you live in zone 5 or warmer, your plan (putting potted trees into the ground) should work just fine.

Thanks Dav4...What I could locate for my climate is that I am a 5B. The only other option I have for the trees is in my attached and unheated garage. In the garage the pots turn solid as if frozen I believe. My thinking, related to putting the pots in the ground, was that the soil area might not go solid. The snow cover would insulate the roots and the natural outdoor moisture would help care.

 

[Dav4]

Any chance you could mulch them in up against the foundation of your house? The slow but steady heat that escapes from your house will provide a slightly warmer micro environment for the trees....they'll still freeze if it gets cold enough without ample snow insulation, but that's ok for temperate trees. In zone 6 MA, my trees would freeze solid (in my unattached garage, and outside, mulched into my veggie garden) in late December and stay frozen until the next March or April....never had a casualty.

 

[Tieball]

Watering the frozen

In zone 6 MA, my trees would freeze solid (in my unattached garage, and outside, mulched into my veggie garden) in late December and stay frozen until the next March or April....never had a casualty.

Dav4
Once frozen as you mention...do you water the trees or just leave them alone at that time until warmth returns in the later part of winter or in early spring?

 

[Dav4]

Dav4
Once frozen as you mention...do you water the trees or just leave them alone at that time until warmth returns in the later part of winter or in early spring?

Once the soil is frozen, the water is unavailable to the trees, so watering is unnecessary and potentially counter productive- picture a block of ice and mulch with your potted tree in the middle of it. The only water I typically applied after the initial watering when the trees were mulched in would be in the form of newly fallen snow. I would pack it in on top of the pots...if it warmed up the snow would melt and water the trees for me.

 

[coppice]

How about watering during the winter....?

This is why providence gave you a finger to check soil with. Or a chopstick if you prefer.

 

[Bill S]

Just don't press real hard with your finger if it is frozen, it might break.