Satsuki Azaleas in Winter

[Paradox]

So I would like to hear from others that are keeping Satsuki azaleas about how much cold exposure do you let them have?
I know they are less cold hardy than the Karume so I was wondering what is the best practice for them.

Where I am in zone 7 they are supposedly hardy in the ground but ones in pots will need to be protected.
Are freezing temperatures safe for Satsuki azaleas in pots?

Thanks

 

[JudyB]

I would not let Satsuki freeze. Mine go in after the first good frost.

 

[Harunobu]

I used to have them potted and moved them inside an unheated shed. But quite a few of them died, I think because of lack of water during cold periods.
Currently, I have all my satsuki in the full ground. I only had frost damage when they woke up too early and mid april frost hit them.

There was one very serious period of -12C frost with strong eastern winds. I remember ice skating on the outskirts of the Rhine during that frost period, but it was so windy my hands were getting so cold, I was really worried about frostbite (too stubborn to use gloves and thinking I can just toughen it out). Pretty sure their roots froze solid. But that frost didn't seem to have harmed any of the buds. But that type of frost might kill weaker internal branches. But you don't notice that on garden shrubs.

In pots, they should behave one zone less hardy. So in that respect it suggests satsuki can survive fine in pots in zone 8.

I intend to keep all my seedlings potted outside at all times. Probably, the first year I will try to do some protection. But after that, I will keep them unprotected to 1) see what happens 2) let the less cold hardy ones die.

 

[Carol 83]

I used to have them potted and moved them inside an unheated shed

That's where I am keeping my one and only along with my crapes and Mulberry. I think I may get a bit colder weather than you? It already has some buds set for spring, will it be OK in there do you think?

 

[Brian Van Fleet]

I leave mine outside year-round. The Kinsai comes in when it gets below 20f, but only because I‘d rather not chance it.

 

[Harunobu]

That's where I am keeping my one and only along with my crapes and Mulberry. I think I may get a bit colder weather than you? It already has some buds set for spring, will it be OK in there do you think?

Most buds set 3 months ago, maybe the slower ones 1.5 months ago.

You didn't set your hardiness zone. IL should be colder than zone 7, right? But US states are large and many of them differ in hardiness internally because of mountains/great lakes/deserts/coastlines/being stretched north to south.

If I bought a bonsai, I would probably put it inside. My problem may have been that I had many plants inside without anything to catch the water. So I rarely watered them. And when they are inside and it starts freezing at 6PM and ends freezing at 8AM, the time they spend outside is quite little. And I have this phobia about watering an azalea, then having the water I just put in their freezing. Not sure if that is a realistic concern. But if I had one bonsai, I could use a tray underneath and just water it properly.

The biggest risk factors seem to be wind drying out the plant once it has the roots frozen. So when it gets windy when a cold front rolls in from the continental north. And very late or very early frost.

 

[jimib]

I only have 1...it’s in a greenhouse between 32/34 degrees..in the winter

 

[Paradox]

Thanks for the responses.
My one and only Satuski is still on the bench outside.
When I went to bed last night, it was 30 deg F and I was like "it shouldnt get colder than that, so it should be ok"
Well the dog woke me up at 3AM and it was 26 degrees F.... I was not happy to see that.
Hopefully it will be ok

I think its still too warm in the garage during the day to keep it in there full time.

 

[jimib]

FWIW mine hit the mid 20’s a time or two before I put it away and it doesn’t seem to have any damage

 

[Harunobu]

26F at this point in the year should be fine. The problem occurs when it gets quite cold in climates that have poor summers. When the frost is really early or really late. Or if you have a really strong frost spell in your zone 7 climates. Most winters, your satsuki bonsai will very likely be fine. But if you have the coldest winter in 5 or 10 years, it can get damaged or potentially die. Or maybe it will be fine. Also depends on your type of zone 7, and the cultivar. Most satsuki are in the range of -5 to 5F as garden plants. And the hardiness usually indicates damage or no blooms, not the entire plant dying. So that may mean 5F could potentially kill your bonsai.

If you get early frost, one should check if it has signs of dormancy already. But I bet yours has. If you have 50F night temperatures all of October and November, and then it suddenly drops to 20F, then that is trouble. Stopping with fertilizer past September also helps it go dormant. But then it needs some colder nights to trigger dormancy fully. Once it is dormant, it can take quite some frost. In zone 8, it can go down to 10F/-12C, and that is likely in the ballpart for what they can take safely when dormant.

My biggest issue with frost has been in spring. Once it has new growth, a single degree below 0C will destroy the new growth, potentially defoliating the plant. Had this happen to my Haru no Sono. But it recovered fine, as if it was pruned completely. That did have me scared a bit though.

 

[Carol 83]

Most buds set 3 months ago, maybe the slower ones 1.5 months ago.

You didn't set your hardiness zone. IL should be colder than zone 7, right? But US states are large and many of them differ in hardiness internally because of mountains/great lakes/deserts/coastlines/being stretched north to south.

If I bought a bonsai, I would probably put it inside. My problem may have been that I had many plants inside without anything to catch the water. So I rarely watered them. And when they are inside and it starts freezing at 6PM and ends freezing at 8AM, the time they spend outside is quite little. And I have this phobia about watering an azalea, then having the water I just put in their freezing. Not sure if that is a realistic concern. But if I had one bonsai, I could use a tray underneath and just water it properly.

The biggest risk factors seem to be wind drying out the plant once it has the roots frozen. So when it gets windy when a cold front rolls in from the continental north. And very late or very early frost.

Hardiness zone 6a. It's a Chinzan, still in a nursery pot. It appears to be fine so far. We have had some hard freezes, but no really cold weather as of yet. Winter is kind of a crapshoot here, some are mild and some are not.

 

[Harunobu]

'Chinzan' should be among the more hardy satsuki. It might be hardy in zone 6 as a garden plant. Probably borderline. (But with climate change your hardiness zone might not be 6 anymore.) As a bonsai or as a potted plant, you are probably wise to protect it during a truly hard winter worthy of zone 6.

If you have a once in a decade winter that is killing plants in your local gardens, many evergreen rhododendron, including azaleas, will be among the victims.

And as a bonsai or potted plant, it will be more vulnerable. But there is quite a difference between a few degrees of frost and a very cold zone 6 winter day. Once it is really cold during the daytime for several days straight, then satsuki will be among the first evergreen azaleas to get damaged. But apparently often through wind drying them out.

 

[Cadillactaste]

I have two satsuki. The one from @Don Blackmond if that's a correct spelling of his name. Tried to tag him to check spelling. And nothing came up under his name. *sorry for the rabbit hole. The one that came from him can have an occasional dip into the teens. The satsuki with the neagari from Scott Lee. I'm to keep it around 35F. So...cultivar plays a huge part in it. If unsure...I would be focused on better safe than sorry. But with having one which can see teens. I wouldn't worry just yet on yours

 

[August44]

I have recently purchased 3 ChinZan Satsuki and am considering a 14" Nikko. Are the Nikko's good bonsai material? I know nothing about Azalais, but sure like what I see so far and the flowers are a great bonus.

 

[Dav4]

My understanding with Satsuki is that they all can take a frost but the more cold hardy varieties will have smaller leaves and be ok with freezes but would prefer to be kept above freezing. I coveted them when I first began my bonsai journey but didn't buy one until my family decided to relocate south as I didn't want the headaches associated with overwintering one in zone 6 MA. Any way, the ones I've kept here in 7b have frozen solid every year but would only stay that way for a day or two as a rule, though sometimes for a week or longer during longer cold stretches- they'd be on the ground and probably mulched with leaves at that point- and they would break dormancy without issue every spring.

 

[johng]

I am in a warmer region than you are but I pack my satsuki on the ground into an area that is wind protected..I do add the 4th wall. I leave them exposed unless temperatures drop into the low 20's and then I cover with blankets. We've already had several low temps this season...5 nights in 20's and lowest was 24 and I have yet to cover and everybody is good.

 

[bwaynef]

Quoting Peter Warren:
"Basically the sap which is just below the paper thin bark will freeze when temps hit -5 and below if not well protected." (For that to make sense of what he's saying, I'm pretty sure he's referring to Celsius.)

Mine have been subjected to 23ºF so far this year. I have one that's weak and brought it into the unheated garage that night. But its back out in ~28ºF temps this past week. (Luckily, for the foreseeable future we're heading back to the low-mid 30s for overnight lows.)

 

[Harunobu]

Nikko and Chinzan are both very good for bonsai, both on the hardy size of satsuki.

Also, Peter Warren is very wrong about that. In fact, a comment like that make me wonder how he finished his physics BSc because if you have one, you should know bark cannot affect temperature like that and you must realize plant cells don't become filled with sharp ice crystals the moment temperatures drop below 0C. If that is how it worked, all plants would die during all winters, until you reach zone 10.
Sap in plants doesn't freeze in winter. That is not how plants die when it gets too cold. That is only how tropical plants die in a freeze. Or plants way outside their hardiness zones. And bark has very little to do with winter hardiness. Why are deciduous azaleas so much hardier than evergreen ones? Because they have thicker bark? No. Plants don't survive winter through insulation.

That said, I think the -5C as an average temperature is a good cutoff point for what you should expose your satsuki bonsai to. And maybe -10C as a minimum temperature. But better to be safe than sorry, of course.

The biggest question to me is the role of soil insulating the roots and keeping temperatures higher than the outside air. How large a difference does this make? Haru no Sono can survive -20C as a garden plant. But what if it is a bonsai in a relatively small pot?
And to what level can you reintroduce this insulating effect by adding insulating material around the pots. Or the way JohnG does it. And his method also helps against desiccating winds when the soil does freeze.

 

[JudyB]

I am in a warmer region than you are but I pack my satsuki on the ground into an area that is wind protected..I do add the 4th wall. I leave them exposed unless temperatures drop into the low 20's and then I cover with blankets. We've already had several low temps this season...5 nights in 20's and lowest was 24 and I have yet to cover and everybody is good.

View attachment 343705

Whoa! And I thought I was azalea obsessed...

 

[johng]

Whoa! And I thought I was azalea obsessed...

That is mostly just the chinzan and wakaebisu. There are a fair number of others. Crazy thing is that I don't even really like azalea accept for accents on rock plantings.