Watering in Fall/Winter

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Hi all,

I am curious about watering habits during Fall/Winter in Zone 6a (or nearby zones). My plants all live in inorganic substrate, and I currently water once a day in the evening. The plants are generally happy and healthy.

With cooler temperatures around the corner, however, I know I'll need to scale back my watering habits. Here's my dilemma: much of the advice I read online says to "test" the soil to know when to water next. I've tried burrowing my finger into my mostly pumice substrate to check for moisture, and it doesn't work. It just feels like rock.

I plan to keep my trees in a small, polyurethane-covered greenhouse over the winter. Any general advice? Yes, I know, I know--it depends on tree species, humidity levels, and a whole host of other factors. :) I'm not looking for nuanced advice. I'm really wondering about how often people find themselves watering their sheltered trees during fall/winter (once a week? once every two weeks? every three days?) and when they make the transition (late September? November?).

Thanks in advance for any help you can provide!
 

canoeguide

Shohin
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Hi all,

I am curious about watering habits during Fall/Winter in Zone 6a (or nearby zones). My plants all live in inorganic substrate, and I currently water once a day in the evening.

Water in the morning if you are able. The trees need the water during the day when it is sunny and hot and they are transpiring, not so much in the middle of the night when it is cool and dark.

When it's consistently below freezing, don't water. That's easy. You can put some snow around your trees so that they will get watered when/if it warms up.

In spring and fall when the temps fluctuate and are either cool or sometimes above and sometimes below freezing, let nature do most of your watering. In your (and my) zone, Oct-Dec and Mar-May usually get plenty of rain to keep bonsai alive. The trees aren't really using very much water then, but if you're using an inorganic substrate, they'll be fine if you water them a bit more than they might need.
 

DonovanC

Shohin
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I’m also in 6a - I hardly water my trees at all during dormancy. As mentioned, it rains/snows pretty consistently during these months and not much is happening to dry up the soil so it stays moist with little effort. When it snows, I pile snow on all my pots.
Just check them a couple times a week, you should be able to tell at a glance if they need water. Regardless of what components you use in your soil, there’s typically a visual difference in dry versus wet.
 
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Trees in frozen soil don’t need to be watered.... put snow on them instead.

I notice a lot of folks here recommending adding snow to the trees. Does this recommendation apply to trees living in a small greenhouse? Except on bitterly cold days, won't the snow immediately melt inside the greenhouse, in effect "watering" them on the spot? I guess I'm just curious how to handle plants in enclosed structures, where rain and snow can't go.
 

DonovanC

Shohin
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I notice a lot of folks here recommending adding snow to the trees. Does this recommendation apply to trees living in a small greenhouse? Except on bitterly cold days, won't the snow immediately melt inside the greenhouse, in effect "watering" them on the spot? I guess I'm just curious how to handle plants in enclosed structures, where rain and snow can't go.

You really just water the same way that you do any other time. If it’s dry, water it. If it’s moist, leave it be. The snow is just so it has some water when it gets warm. It might add some protection as well, but I don’t know that to be tree.
The only thing that’s different in winter is that the need to water is much less often. Pots don’t really dry out much when the temperatures are really low.
 

canoeguide

Shohin
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I notice a lot of folks here recommending adding snow to the trees. Does this recommendation apply to trees living in a small greenhouse? Except on bitterly cold days, won't the snow immediately melt inside the greenhouse, in effect "watering" them on the spot? I guess I'm just curious how to handle plants in enclosed structures, where rain and snow can't go.

That depends on how warm you're keeping the greenhouse. It seems the winter goal of most people on this site is to protect trees from winds, rodents, and freeze/thaw cycles. The desire is generally not to protect hardy trees from freezing. Keeping trees in a greenhouse where temperatures can swing wildly based on outdoor air temp and sunlight is not recommended.

My personal goal for hardy trees is to let them get cold and keep them there, which is why they are placed in full shade and in/on the ground for the winter. In 6a, they get the odd warm day(s), and this is when the snow melts and waters them.
 

Vali

Mame
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I don't think that trees need a lot of water during dormancy. I also don't think I've watered my trees more than 5 times last winter. I use baked clay granules with perlite, covered with a layer of sphagnum moss as substrate and it was frozen most of the time until about february. At that time I took them in a cold room in my house because the night temps got below -20 C. None of them seems to have had a problem with that.
 

PA_Penjing

Shohin
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Canoeguide's last comment is important. You haven't said which species you are growing, but keeping hardy trees in a greenhouse so warm that it melts snow instantly is not good news. If you have any larch, amur maple, jack pine, siberian elm etc. The best place for them is outdoors in the shade where precipitation will keep them pretty well watered. I personally do the snow thing like everyone else. My very hardy trees (jack pine, american larch) just get placed against a fence for the winter and I might not water them once all season if it's wet. where as my less hardy trees (JM,trident,BC) get put in a garage if it falls below 25 degrees. Those might need a watering every 7 to 10 days (indoors) depending on substrate or how recently it rained when they were outside. there's too many factors to put this one on a calendar but as I understand you're just getting a rough idea of what to expect.
I don't know if you are new to the hobby or not, so I don't want to insult you. But every January/February/March there's a barrage of beginners on Bnut posting "help me" threads because their trees came out of dormancy and began growing in the dead of winter. It's not an easy problem to fix, and if it doesn't kill the tree it will definitely set it back. I know you didn't ask for help with your winter set up but I'm just trying to be helpful. Most trees are much hardier than folks like to think. AGAIN though, this is also all species dependent
 
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I don't know if you are new to the hobby or not, so I don't want to insult you. But every January/February/March there's a barrage of beginners on Bnut posting "help me" threads because their trees came out of dormancy and began growing in the dead of winter. It's not an easy problem to fix, and if it doesn't kill the tree it will definitely set it back. I know you didn't ask for help with your winter set up but I'm just trying to be helpful. Most trees are much hardier than folks like to think. AGAIN though, this is also all species dependent

Thanks. This is quite helpful, as is @canoeguide's comment. I didn't mean to suggest the greenhouse will be hot. I do expect it to stay mostly above freezing though. It's not heated or anything, but I assume sunlight will be enough to keep the temps above 32F through most of an Indiana winter. So, my comment about snow melting applies in a situation where the trees are (1) in the greenhouse, (2) dormant because cold, (3) but still susceptible to melting snow if added inside.

As for tree species, I have: BC, Trident, Ponderosa Pine, Azalea, and a Juniper Nana. I suppose the Ponderosa and JN can pretty easily survive outside the greenhouse. I plan to place the others in the house. I just didn't know how to water the in-house ones because obviously they will receive no natural water from rain/snow.

Thanks again. If you have any other advice, I'm all ears!
 
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So I’m in a bit warmer zone, yet I water only once a month max with trees in my cold frame tents. The big issue I have, besides the 2-3 times a winter snowfall collapsing the tents, is being concerned about fungus.

So I keep it a bit drafty inside each during the day unless it’s way cold and hit the trees with a fungicide once in awhile.

Oh yes, I keep the junipers away from the deciduous trees, especially fruit trees.

cheers
DSD sends
 

Forsoothe!

Imperial Masterpiece
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When my trees are put outdoors, in full sun, on the ground in November, they don't get watered until they go back to the bench in late April. I guess I'm lucky with a good climate.
 

leatherback

The Treedeemer
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Mind normally do not get handwatered from somewhere oktober to march. I let nature do its job and provide.
 
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Just want to see what the thoughts are for "hardiness" for the following species if planting underground is not an option... but it is possible to keep on the ground-in the corner of a fence and large bushes.

My options for wintering these species is having it protected by a giant cedar and the fence or having it near a drafty garage door (drafty is noted because it keeps the garage close to outside temperatures)



Tree species-

Thuja occidentalis
Buxu sempiverens
Potentilla cinquefoil
Wegelia wine and roses

Winters where i am get hit with snow squalls, ice storms, freezing rain and can easily fall to -30 C windchill
 

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