Satsuki Azalea winter leaf drop

[lauralee]

This will be my satsuki's first winter in zone 6. The plan is to keep it outside in a protected spot, with pot buried in soil/mulch. Two questions:
1) do satsukis typically drop leaves when Temps go below 20° F?
2) if there is little or no snow, is it safe to water?
Thanks for any insights.

 

[Cadillactaste]

Depends on cultivar. I've one that can't go below 30f...and another that can see teens occasionally.

Do you know the cultivar you own as to how cold hardy it is?

My satsuki get fall colors and shed those leaves.

This one can't go below 30f... it will drop the fall colors.

 

[lauralee]

I don't know the cultivar, which would help.
Maybe best to just bring it into the garage for winter.

 

[rockm]

I don't know the cultivar, which would help.
Maybe best to just bring it into the garage for winter.

I'm no expert, but I've heard thinner leaves indicate a more cold-hardy cultivar. Wider leaves indicate more cold sensitive variety.

Zone 6 could be problematic for any satsuki exposed to the worst, though. Also anecdotal, but I have a friend who brought satsukis into his unheated garage for the winter. The results weren't great.

The Satsuki Society says most varieties are hardy to 0 F, some to -10 F, but that's for plants in the ground. Some say satsukis do best in Zones 7-9. I'm in Zone 7.

FWIW, I have a couple satsukis one is Shiro Ebisu, the other is Hinomaru. I have overwintered the Shiro Ebisu outside under mulch for the last ten years. It doesn't have a problem with it, but is an extremely vigorous plant. It has had single digits in Jan. It has frozen solid and leaves droop when that happens. It perks up as temps get above freezing.

I have overwintered the Hinomaru in a cold greenhouse for the last few years since I got it. It doesn't seem as hardy as the Shiro Ebisu.

Bottom line is you have to guess what will work.

 

[Cadillactaste]

I don't know the cultivar, which would help.
Maybe best to just bring it into the garage for winter.

Might be wise...since you are unaware. Have you used that area for wintering? Hot winter days...you will need to vent/open things up or it will get to warm.

I have a thermometer with a sensor to alert me if it gets to warm...or...to cold. I'll turn on the secondary heat.

Don't forget to water it.

 

[lauralee]

Thanks for your replies. Plan to overwinter in-ground with protective enclosure that can be vented.
Thanks again!

 

[Glaucus]

1) They drop leaves late September to October. About half of the leaves can drop. They will turn yellow or purplish first, then drop. The smaller leaves around the flower buds will remain.
2) Plants need water in winter as well. If there is a little bit of snow, and it melts, it will water the plant, a little bit. Once it is frozen solid, it cannot take up liquid water. So when the ground thaws, and there is no rain, you water.

There's no reason to water if the liquid will turn solid very quickly anyway. There is debate both ways about if watering when the soil is prone to freezing, for example during night time. One theory is that water has a high heat capacity and thus will prevent freezing, or freeze and thus absorb the cold/release heat. The other theory is that if you add water, you will get more expanding water crystals. Either outside of the plant, near the roots, inside the roots but extracellur, or intracelluar. With the ice crystal puncuting cell membranes, destroying those cells. Dealing with ice crystals in tissue when the water inside a cell freezes is one of the main challenges plants face. And thus one of the main areas where plants have all kinds of tricks to cope with this.
How many of these tricks a plant has in part decides their winter hardiness.

As mature plants, in full soil, satsuki are hardy to zone 7, some of them zone 6. And of course your average winter in zone 6 is likely to only experience zone 7 or even zone 8 weather.
Zones are rated by their extremes. And the trend is towards warmer winters. But of course being in zone 6 and betting on only zone 7 winters to occur is not a wise long-term strategy. Who knows if winter 2024-2023 will be that outlier winter that makes a zone 6, a zone 6.

Note that inside pots, plants are one zone less hardy. And inside bonsai pots, that might be 1.5 zones. If the plant is small or unhealthy, it may add another zone point

 

[lauralee]

Glaucoma,
Thanks for your input. The plan is for an in-ground (no pot) protected spot. Watering will be tricky, but just have to assess as we go.
Thanks again!

 

[lauralee]

Glaucoma,
Thanks for your input. The plan is for an in-ground (no pot) protected spot. Watering will be tricky, but just have to assess as we go.
Thanks again!

GLAUCUS, auto correct messed up your name. Apologies.

 

[rockm]

1) They drop leaves late September to October. About half of the leaves can drop. They will turn yellow or purplish first, then drop. The smaller leaves around the flower buds will remain.
2) Plants need water in winter as well. If there is a little bit of snow, and it melts, it will water the plant, a little bit. Once it is frozen solid, it cannot take up liquid water. So when the ground thaws, and there is no rain, you water.

There's no reason to water if the liquid will turn solid very quickly anyway. There is debate both ways about if watering when the soil is prone to freezing, for example during night time. One theory is that water has a high heat capacity and thus will prevent freezing, or freeze and thus absorb the cold/release heat. The other theory is that if you add water, you will get more expanding water crystals. Either outside of the plant, near the roots, inside the roots but extracellur, or intracelluar. With the ice crystal puncuting cell membranes, destroying those cells. Dealing with ice crystals in tissue when the water inside a cell freezes is one of the main challenges plants face. And thus one of the main areas where plants have all kinds of tricks to cope with this.
How many of these tricks a plant has in part decides their winter hardiness.

As mature plants, in full soil, satsuki are hardy to zone 7, some of them zone 6. And of course your average winter in zone 6 is likely to only experience zone 7 or even zone 8 weather.
Zones are rated by their extremes. And the trend is towards warmer winters. But of course being in zone 6 and betting on only zone 7 winters to occur is not a wise long-term strategy. Who knows if winter 2024-2023 will be that outlier winter that makes a zone 6, a zone 6.

Note that inside pots, plants are one zone less hardy. And inside bonsai pots, that might be 1.5 zones. If the plant is small or unhealthy, it may add another zone point

Is there a debate about extra, inter and intra cellular freezing in plants?

FWIW, The "theory" that water can act as an insulator is not a theory. It's thermodynamics. Water also gives off heat as it freezes, also a thermodynamic fact..

 

[Glaucus]

Yes, that's very true. The point is that plants pump water out of their cells into the extra-cellular space. This way, the concentration inside the cells is very high, so the freezing temperature of that water goes way below 0C (could be -40C or even lower for some species of Pinus and Abies, Strimbeck et al. 2015.) Plants can't insulate. Once the air temperatuer drops that low, the temperature inside the cells also have to drop. And plants actually get rid of their water inside cell membranes to survive winter.
But the water outside of the cells, but inside the plant tissue, can still freeze, and become crystalline. But plants then have proteins to limit the size of these crystals, so they are not sharp and pointy, puncturing cell membranes.
This extends to a thinking that a soil full of water freezing solid might be worse than a soil drained of water going below freezing.
It is true that the water-soaked soil, or substrate, will possibly not freeze because of the water.
The thing that to me at least is an open question is whether it is always better to have a water-soaked pot when the lowest winter temperatures hit, temperatures that can potentially get low enough to remove all the heat of the water making it drop to 0C, but then also overcoming the enthalpy of fusion, and freezing the water.

But the difference is great. With the energy released by freezing water, you could heat up that same water from 0 to 79 degrees C. This is because the hydrogen bonding in water is really strong. And when going from ice to liquid, these all need to be broken. Hence, the reverse happens when freezing. Which is why they spray water on the blossoms of fruit trees during spring frost. Which often means that blossoms could be embedded in ice, but stay 'warm' exactly because of that.

Our brain logic would think that putting a apple blossom inside ice will destroy it. But the energy it kind of releases may make sure that the temperature of the cells inside the apple blossom don't drop too far below 0C or stay very near 0C, meaning the water inside those cells easily stays liquid.
But intuitively, us deliberately spraying water on our bonsai, only to see it all embedded in ice the next morning, it doesn't feel good to do.
I'd be happy to hear from people who have actually sprayed water all over their bonsai just before frost hits.

Why Italian Apple Farmers Are Coating Their Orchards in Ice

Freezing the trees, blossoms and all, may be the only way to save the crop.

www.atlasobscura.com

Deep Sea Diver also did a kind of literature review on winter hardiness and the adaptations done during dormancy.

Overwintering bonsai – Theory, Planning and Case Studies Azalea Focus

Greetings! Winter is approaching and this resource is all about wintering over bonsai! The theory, planning and case studies within the guide are applicable to all temperate bonsai. While azaleas are used as the primary focus in some parts of...

www.bonsainut.com

 

[rockm]

Yes, that's very true. The point is that plants pump water out of their cells into the extra-cellular space. This way, the concentration inside the cells is very high, so the freezing temperature of that water goes way below 0C (could be -40C or even lower for some species of Pinus and Abies, Strimbeck et al. 2015.) Plants can't insulate. Once the air temperatuer drops that low, the temperature inside the cells also have to drop. And plants actually get rid of their water inside cell membranes to survive winter.
But the water outside of the cells, but inside the plant tissue, can still freeze, and become crystalline. But plants then have proteins to limit the size of these crystals, so they are not sharp and pointy, puncturing cell membranes.
This extends to a thinking that a soil full of water freezing solid might be worse than a soil drained of water going below freezing.
It is true that the water-soaked soil, or substrate, will possibly not freeze because of the water.
The thing that to me at least is an open question is whether it is always better to have a water-soaked pot when the lowest winter temperatures hit, temperatures that can potentially get low enough to remove all the heat of the water making it drop to 0C, but then also overcoming the enthalpy of fusion, and freezing the water.

But the difference is great. With the energy released by freezing water, you could heat up that same water from 0 to 79 degrees C. This is because the hydrogen bonding in water is really strong. And when going from ice to liquid, these all need to be broken. Hence, the reverse happens when freezing. Which is why they spray water on the blossoms of fruit trees during spring frost. Which often means that blossoms could be embedded in ice, but stay 'warm' exactly because of that.

Our brain logic would think that putting a apple blossom inside ice will destroy it. But the energy it kind of releases may make sure that the temperature of the cells inside the apple blossom don't drop too far below 0C or stay very near 0C, meaning the water inside those cells easily stays liquid.
But intuitively, us deliberately spraying water on our bonsai, only to see it all embedded in ice the next morning, it doesn't feel good to do.
I'd be happy to hear from people who have actually sprayed water all over their bonsai just before frost hits.

Why Italian Apple Farmers Are Coating Their Orchards in Ice

Freezing the trees, blossoms and all, may be the only way to save the crop.

www.atlasobscura.com

Deep Sea Diver also did a kind of literature review on winter hardiness and the adaptations done during dormancy.

Overwintering bonsai – Theory, Planning and Case Studies Azalea Focus

Greetings! Winter is approaching and this resource is all about wintering over bonsai! The theory, planning and case studies within the guide are applicable to all temperate bonsai. While azaleas are used as the primary focus in some parts of...

www.bonsainut.com

I spray my trees on early spring mornings when lighter frost is around and new foliage is emerging on bonsai. I'm typically up before the sun and late frosts settle in the hour or so just before dawn. It definitely keeps the frost off of new foliage. On the other side of the seasons, I make sure my trees are well-watered when frosts and freezes are forecast in Oct. and Nov. I also make sure they don't dry out in winter storage. Free water in pots slows down the freezing process and ice around roots can shield them from the harshest of the cold. I learned the hard way that letting pots go too dry in winter is a death sentence for the tree for the most part.