High winter temps

[tstrum]

Besides a few random days of 20 degree weather, we are having a warm winter. Looking at the forecast we are projected to have 5 days in a row of highs above 50 degrees and lows between 30-40 degrees. I am concerned about my trees prematurely ending dormancy with more freezing weather likely during January and even into February. My questions and concerns are:
1) what are the actual conditions necessary for a tree to break dormancy? (I've heard it something like 72 hours about 50 degrees, but is that condition not met if lows are well below 50?)
2) What steps should be taken to protect a tree should it break dormancy too early?
3) knowing the expected temps may induce early growth, is there anything I can do to keep the trees breaking dormancy?

 

[Zach Smith]

Your best bet is to create a ground bed that's cut below grade and filled with bedding soil or something similar, that will stay cooler than your benches do when the temps get too warm. Heat on the roots is worse than heat on the above-ground parts of your trees.

Zach

 

[Dav4]

Different species have varying chilling requirements that need to be met before breaking dormancy, so it's different from one to another and I wouldn't worry too much about that. Also, a tree that breaks dormancy is expecting temps above freezing and spring-like sunshine, which you will be needing to provide regardless of the time of year... fwiw, I doubt your trees are at risk of breaking dormancy right now, but in 4-6 weeks all bets are off. The bottom line is that from now until your trees actually start to grow, you want to keep them as cold as possible. If the trees are being kept in an outdoor enclosure, I'd want all the doors and windows wide open at night so as much cool air gets inside. If the enclosure is in shade or the skies are cloudy or rainy, I'd actually keep them shut during the day to trap the cool air inside. If you're keep the trees outside, you've hopefully sited them appropriately in a place out of the sun and wind, and mulched over the pots. If you haven't, that's where I'd start.

 

[namnhi]

This first week of winter has been summer like for us. We celebrate X-mas in short and AC has to be on again. Has been consistently above 80 for the last few days as well as the next few days. Long range forecast has the highs in the mid 70s and the lows in the mid 50s. I don't remember it has been this warm for a little while.

 

[c54fun]

Besides a few random days of 20 degree weather, we are having a warm winter. Looking at the forecast we are projected to have 5 days in a row of highs above 50 degrees and lows between 30-40 degrees. I am concerned about my trees prematurely ending dormancy with more freezing weather likely during January and even into February. My questions and concerns are:
1) what are the actual conditions necessary for a tree to break dormancy? (I've heard it something like 72 hours about 50 degrees, but is that condition not met if lows are well below 50?)
2) What steps should be taken to protect a tree should it break dormancy too early?
3) knowing the expected temps may induce early growth, is there anything I can do to keep the trees breaking dormancy?

I'm going by a rule of thumb 40 days at 40 degrees. This comes from a seller and a collector of a lot of nice bonsai. Many different numbers if you look around.

I'm in Dallas and we are having warm weather also. I have a couple of trees I want to stay as cold as possible so I did this with them (don't laugh). Helps keep them cold on warmer days. I keep them off the ground and out of the direct sun and also away from the house. This may or may not help. Its just what I'm doing. Cant say I would recommend this. Best to have trees that fit your weather patterns.

 

[sorce]

Best to have trees that fit your weather patterns.

Agreed.

That is a wicked rig!

Sorce

 

[c54fun]

It was 75 today. Nice and cold in the cooler.

 

[Leo in N E Illinois]

ON the ground, or pots buried in the ground, in the shade as Zach recommends, would be my advice too. It is important to keep them out of the sun.

Once they start growing, there is no stopping them, though some species will bounce back well from late frosts. This is a species by species trait. Junipers handle late frosts reasonably well. You may loose some of your deciduous with a late frost. Flowers may die, but often the tree will produce a second round of vegetative buds. It is species by species in terms of response.

Once they start growing, you have to do the "in and out dance". Bring them into a protected area, or indoors for frosty nights.

 

[miker]

C54 fun, what a fantastic idea and less extreme(and more workable for conifers) than the fridge. Do you fill the coolers with ice every few days and have a drain in the bottom?

That method takes some continuous work, but I wonder if keeping the roots near freezing for a couple months this way would enable many temperate bonsai to thrive in a place like Central Fl( or JWP in Dallas)?

Is the root zone temperature enough to satisfy chilling requirements or do the above ground dormant buds have to be exposed to the same, or at least some chill as well? I suspect the latter, but this could certainly help fully satisfy a tree's requirements when the roots are cold enough but the rest of the plant stays marginally too warm.

 

[c54fun]

C54 fun, what a fantastic idea and less extreme(and more workable for conifers) than the fridge. Do you fill the coolers with ice every few days and have a drain in the bottom?

That method takes some continuous work, but I wonder if keeping the roots near freezing for a couple months this way would enable many temperate bonsai to thrive in a place like Central Fl( or JWP in Dallas)?

Is the root zone temperature enough to satisfy chilling requirements or do the above ground dormant buds have to be exposed to the same, or at least some chill as well? I suspect the latter, but this could certainly help fully satisfy a tree's requirements when the roots are cold enough but the rest of the plant stays marginally too warm.

I use freezable gel packs. Works great. Gives me a chance to also look at the tree to make sure all is good with it when I swap out the packs. This is my first year trying this and I hope it is enough to allow the trees to grow well and not slowly die. I guess time will tell if just keeping the roots cold will work.

Larch is one of my favorite trees but they need lots of cold and not lots of heat. No good for Texas. I bought a small one and I'm using this method on it also.

The couple months that's super hot in Dallas I will have the trees in a small air conditioned greenhouse. If I can keep them cold in the winter and also keep from baking them in the summer maybe they will grow well??? If not, lesson learned.

 

[tstrum]

I'm going by a rule of thumb 40 days at 40 degrees. This comes from a seller and a collector of a lot of nice bonsai. Many different numbers if you look around.

I'm in Dallas and we are having warm weather also. I have a couple of trees I want to stay as cold as possible so I did this with them (don't laugh). Helps keep them cold on warmer days. I keep them off the ground and out of the direct sun and also away from the house. This may or may not help. Its just what I'm doing. Cant say I would recommend this. Best to have trees that fit your weather patterns.

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Just to confirm: when you say 40 for 40 days are you referring to the chill time or that's the general rule of thumb for breaking dormancy?

 

[tstrum]

Thank you all for the great advice and tips!

 

[c54fun]

Just to confirm: when you say 40 for 40 days are you referring to the chill time or that's the general rule of thumb for breaking dormancy?

Chill time. I'm hoping to get 75 days of less than 40 degrees. Half of December, Jan and Feb.

 

[M. Frary]

I'm loving it.
No below zero temps yet.
We got a little over a foot of snow that's melted and frozen and is now ice with a little fresh snow on top.
My trees are encased in it.
Good to go for the rest of winter.

 

[tstrum]

I apologize if I am misunderstanding something but I'm still not quite sure what the conditions are that will cause a tree to break dormancy. "X" number of days with lows above "y" will likely lead to starting to grow.

 

[Dav4]

I apologize if I am misunderstanding something but I'm still not quite sure what the conditions are that will cause a tree to break dormancy. "X" number of days with lows above "y" will likely lead to starting to grow.

More or less- Once the chill requirements are met, and the temperature warms for a bit (in my experience, any ambient air temp over 40 F for a few days may start things rolling for a tree in a pot, though soil temps seem more important in the breaking of dormancy, btw) a tree may begin it's spring push.

 

[tstrum]

Oh gotcha! I took chill time to mean an ideal dormancy period for a tree to have a good spring, not as an out and out requirement that had to be met. My concern with our warm weather was breaking dormancy before hitting the chill requirement and therefore having a poor growing season.

I follow now. Thank you!

 

[just.wing.it]

70℉ here today!

 

[namnhi]

My potted Japanese Maple is about to push leaves. We have had so many days in the high 70s and low in the 60s. We have a mild winter this year.

 

[Dav4]

Oh gotcha! I took chill time to mean an ideal dormancy period for a tree to have a good spring, not as an out and out requirement that had to be met. My concern with our warm weather was breaking dormancy before hitting the chill requirement and therefore having a poor growing season.

I follow now. Thank you!

Heh heh, I should tell you that, early in my bonsai experience, I tried to overwinter some trees in a cold basement where the temps were above 40 F and the trees started to push leaves after 3-4 weeks, which was in early January. I would suggest that the chill requirements hadn't been completely met, but the extended warmth pushed the tree to start growing.