Satsuki Azalea Dormancy

mister_project

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I am a novice and just got through my first spring/summer with my young Satsuki azalea. It almost doubled in size, and it seems to have been a pretty successful growing season in terms of letting it get established in the pot. The tree has been outside on my patio for the whole season, so it got AM sun and was shaded in the PM. Now that fall has hit here I'm wondering about how to properly transition to dormancy. I have had a lot of issues with delayed temperature shock with my "easy to grow" wisteria bonsai, which oddly enough has been the most challenging bonsai I've tried yet... Anyway, I'm nervous about the process since I thought azaleas were supposed to be even a little more finnicky than some of the other trees I have. I live in the Seattle area and the forecast is that lows are supposed to start hitting 42-44F pretty consistently for the next week and will only get back up to 45-48F the week after that.

From my research, what I've been planning on doing is once temperatures starts dropping below 45F (now, pretty much) I should move the tree inside to a cool room where temps stay between 35F-55F. After the tree is dormant I should put the tree in a safe spot and mulch around it up to the rim of its pot for the winter. I'm trying to piece this together from online guides and have a few questions.

Dormancy transition step:
1) The cool room between 35F-55F sounds like my garage would work well. As I write this it is 47F outside and the garage is still at 56F. The garage gets afternoon sun, and since it is uninsulated it does tend to fluctuate in temperature a little bit more than an insulated room. Does the temperature of this location need to be relatively stable or are swings just like it would see outside still okay? This is just to let the tree still get sun and prepare for dormancy, so this is really just about keeping it above ~45F right?
2) I assume that good light is still needed for this stage since the tree still has leaves and is not yet dormant. The garage does have a small window, but again gets PM sun and it definitely wouldn't receive as much sun as it currently does. I worry that the change from AM sun to PM sun would be a shock to the tree. Is this or the amount of light an issue during transition?

Dormancy step:
1) The guides just said "safe spot." Does that mean leave the tree in the garage, move it back outside, or something else? Does it not matter since it has no leaves, and controlling temperature and moisture are really my only main concerns other than pests/rodents? I don't think light matters at all once in dormancy, but please correct me if wrong.
2) How will I know when the tree is dormant? Is it simply once all the leaves drop? I wonder if this was part of the shock problem I mentioned with the wisteria.
3) I assume that mulching the base is just to protect the roots from severe cold and probably to minimize the temperature swings that the tree experiences. Does this mulching happen even if the tree stays indoors or is this only done for the method where people dig a hole in their back yard, put the trees in, and cover it? And just to be doubly sure, I should NOT mulch up onto the tree itself right? The new wisteria info I have for this year says to mulch up to the first branch. I know these are different trees so I'd rather not make bad assumptions.
4) What should I be doing for watering during dormancy? For my wisteria I placed it in a shallow tray with water. This seemed to work amazingly well until it was time to bring the tree out of dormancy, at which point it had some sort of delayed shock and dropped all of its new leaves in spring.

I would prefer not to dig a hole in my back yard and winter the tree there if possible because we have dogs and all sorts of animals around that might mess with it. I'll certainly do it if that's what it takes, but if you can recommend practices that don't require that it would be ideal. I'm being picky, I know. ☺️ Please feel free to set me bluntly set me straight if warranted. It's good for me sometimes.

Thanks for all your input and help! If you have tips for when/how to bring the tree out of dormancy I am all ears as well.
 

bwaynef

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My Satsuki stay outside during winter. They're also evergreen. I generally huddle my better trees together near the house when it gets to about 20ºF, and if it dips into the teens regularly I'll bring them into my unheated garage. My stock plants (in pots) stay on the ground and don't look any worse for it.
 

Harunobu

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Isn't Seattle temperate enough that it is better off outside except for extreme winter weather?
 

Leo in N E Illinois

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@mister_project
Please edit your profile to include your location. In all that typing you did not mention where you live. If you put it in your profile, we won't have to ask. Satsuki azalea generally are hardy through zone 8, many are hardy into zone 7 and some are hardy to zone 6b. A where would help get you appropriate advice.

2nd. If temperatures are above 40 F, the azalea will need light. Light equal to about a half day of sun is needed if you store your azalea "too warm".

If you store your azalea between 32 F to 40 F, you do not need light. It is only below 40 F that azalea are completely dormant.

Storing azalea above 40 F in dark conditions will slowly weaken the tree over winter.
 

mister_project

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My Satsuki stay outside during winter. They're also evergreen. I generally huddle my better trees together near the house when it gets to about 20ºF, and if it dips into the teens regularly I'll bring them into my unheated garage. My stock plants (in pots) stay on the ground and don't look any worse for it.
I read that below 45F was bad for them. If you're telling me that 20F is fine I'll defer to you and leave them out. It sounds like the occasional dip to 15F is not a big deal but I should bring it in at night if it happens consistently? Thank you!
 

mister_project

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Isn't Seattle temperate enough that it is better off outside except for extreme winter weather?
I don't know what "temperate enough" means for this tree. 45F was the number I found online originally and we definitely get colder than that. Bwaynef's post indicates that 20F is fine, in which case that would probably line up pretty well with Seattle. Last winter February had a week or two with lows around 20F, but 30F is probably more typical.
 

mister_project

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@mister_project
Please edit your profile to include your location. In all that typing you did not mention where you live. If you put it in your profile, we won't have to ask. Satsuki azalea generally are hardy through zone 8, many are hardy into zone 7 and some are hardy to zone 6b. A where would help get you appropriate advice.

2nd. If temperatures are above 40 F, the azalea will need light. Light equal to about a half day of sun is needed if you store your azalea "too warm".

If you store your azalea between 32 F to 40 F, you do not need light. It is only below 40 F that azalea are completely dormant.

Storing azalea above 40 F in dark conditions will slowly weaken the tree over winter.
Sure, I'd be happy to update my profile with that helpful info, although my ego can't help but to point out that I actually did say where I lived in the last sentence of the very first paragraph of all that typing. I stated, "I live in the Seattle area and the forecast is that lows are supposed to start hitting 42-44F pretty consistently for the next week and will only get back up to 45-48F the week after that." Adding it to my profile will only help get help from you all, which I am very thankful for so I will do that right after this.

Thanks for the helpful info you gave too. It sounds like my garage is not the best place for the tree. do you know what the minimum temperature I should be concerned about is? We get lows in the 20's-30's. It sounds like I should just leave the tree outside and it'll have the proper conditions it needs. Do you agree with that?
 

bwaynef

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We've gotten down to 6 or 8ºF in the past 3-4 winters. At that point they go into my unheated garage (that my kids leave open on a whim.) While I tried to protect most of mine, a grower friend of mine 40 minutes from me has WAY too many to move so they just sit where they've sat all year: on the ground. They're fine come spring. I'd suggest protecting them well before 8ºF, but there's that.
 

Harunobu

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I don't know what "temperate enough" means for this tree. 45F was the number I found online originally and we definitely get colder than that. Bwaynef's post indicates that 20F is fine, in which case that would probably line up pretty well with Seattle. Last winter February had a week or two with lows around 20F, but 30F is probably more typical.

What is the cultivar? Most satsuki as mature plants in full soil with a good summer and time to go dormant will be hardy to 5 to -5 F. Some may be more tender, though. Of course, a potted plant will not be as hardy. And with a bonsai you won't want to take chances. But 45F is way above freezing. There is also some risk involved in putting your potted azalea in unheated shed that is actually too warm. Leo has some good experience and advice. I used to be afraid for my potted azaleas and I put them all inside during a decent frost (below 20F). But I had much much better success now that I put all my plants into the full ground. There has been a really cold winter with a chill factor near -18C at some point. I remember ice skating on natural ice and it was so so windy. I had more die trying to winter them inside in pots than I had putting them in the full soil. Now, I will try to just keep them outside in zone 7 and protect them from wind.

Anyway, moving them inside after they froze solid, having them unfreeze again, then moving them back outside, and they freeze again, that's bad as well. So having a solid plan is important.

With a zone 8 I would think that only moving them inside if there is a really sudden early or late frost spell is an option. If you get a frost period mid-winter that is ordinary for a zone 8, then likely they will be fine. Protect from the wind for sure. Usually what kills azaleas is the wind drying out a plant that cannot take up water because it is all ice. And with azalea specifically you can have bark split when the azalea doesn't go dormant early enough. Bark splitting is often linked to fertilizing in autumn. I think putting them inside at 45F all winter in zone 8 may actually cause more harm than the frost you may have during most winters. But if it gets really cold, you also don't want your bonsai to die. I just can't say I have good experience with an unheated garage/shed.
 
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shinmai

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First, any published hardiness info is based on trees in the ground. Add 10 degrees for a tree in a pot. Satsuki, and most rhododendron azaleas need a minimum of forty days below forty degrees for dormancy. In my experience if you let them get below 25 degrees, you’re in the danger zone. You can suffer cold damage that will kill the flower buds, and there is also the risk of bark split. Satsuki do not drop their leaves—while frequently called evergreen, they are actually semi-deciduous, in that they replace about half their foliage annually.
While dormant, they are still [barely] photosynthesizing, but their water uptake drops by about 80%. You need only water enough to keep the roots from drying out.
I’m in 5b, where we can get temperatures in the teens below zero. Our winter months tend to be windy, which can dry a pot out in a very short time. All of my azaleas spend the winter in a 6’ by 6’ greenhouse, with a thermostatic controller, two space heaters, and a constant fan for air circulation. The controller is set for a range of 34 to 39 degrees.
 

Leo in N E Illinois

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If you don't know the specific cultivar, the general guide is for satsuki somewhere about +25 F or -4 C is about as cold as I let my Satsuki azalea get. Some of the "florist's azalea" are not quite as hardy, I bring my "florist's azalea" in at about freezing. My named satsuki I bring in at about +25 F. They go into my well house which stays just barely above freezing, usually below 40 F (+4 C).

Where ever you got the advice that satsuki can not tolerate temperatures below 45 F was just plain wrong. The information was likely about how azaleas are kept for "forcing". Some greenhouse operations will keep them growing all winter for their commercial needs. This has nothing to do with what satsuki will actually tolerate.

Also, while barely above freezing is the only way to get full complete dormancy in an azalea, there are people who successfully grow satsuki at elevation in Hawaii, where it is not possible to get temperatures anywhere near as cold as we use for traditional winter care. I don't know the details, but there are articles from the Univ. of Hawaii Ag Department about azalea.

I do not have an indoor space bright enough to keep azaleas growing all winter, so I winter them in my cold well house. Usually 34 F to 40 F. I put them there after a few nights have dipped to about 28 F degrees, I don't panic if it get as cold as 25 F, around -4 C.
 

Deep Sea Diver

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I live just across the lake from you and have a couple different ways to care for Satsuki during the winter. Older plants can be in ground in a sheltered location. I sometimes use a clear vinyl windscreen on either side of the rows running east to west to protect from the SSW and NNW winds. (Storms from the North usually bring snow and freezing temps, from the South snow and usually barely freezing temps). Also we keep the Satsuki at the Pacific Bonsai museum in ground in the open or under cover on benches, but they are all way older.

If the Satsuki is in a bonsai pot or training pot and have been in the pot for at least since late last winter, I put these in a large vinyl cold frame, partially dug into the ground with good drainage covered with large bark nuggets over the media (just large nuggets, not the little stuff.) The air frame is normally open except for cold snaps below 32F. Then it’s closed until the temp is above 32. Some days it’s open during the day, closed at night, some days open all day, some days closed all day. Water only as needed, which isnt much as the soil is pretty damp out here.

Satsuki in their first year in plastic nursery pots, are in my garage, growing out under LED lights and heat mats. Some exceptions from the cold frame are cultivars that I feel are more sensitive to the cold, these are in the garage under natural light, or LEDs as I deem necessary.

Do not worry a lot about afternoon natural light up here. The sun is pretty low most of the winter to do any damage. If you do feel the light is too strong, go to a hardware store and get a foot or two of black plastic screening and fashion a sun screen for those clear days.

Finally all evergreen azaleas, including Satsuki are dimorphic, producing spring leaves and summer leaves. Spring leaves often drop when things turn cooler and windy. Sometimes you lose all the summer leaves too during the winter with outside azaleas, especially Satsuki. Hang in there and don’t panic, 99% of the time they’ll be fine and pop out spring leaves when the weather starts moderating. However, if the trunk splits, that’s a bigger deal requiring immediate first aid... tight parafilm wrap with cut paste etc....

Best of luck! You can PM me if you need more info as the winter evolves.

cheers,
DSD sends

BTW, all my potted plants, except the whips, are still out in the garden area soaking up the sun and rain right now.
 

Claudinei

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Very good Tips, thanks
Its my first Winter with satsuki, I’m just worry because I bought a lot of then, to have it ready with me for the next blooming season, now I moved them to a green house to be there until the winter is over.
here in Belgium is not very cold on winter, so I think it’ll be ok.
 

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