OK, I think I pretty much know the answer to this but I’m going to ask anyway. Does anybody know if you can overwinter potted persimmons by letting them sit on the ground all winter in zone 5b? Especially if there is snow cover?
I have overwintered potted plants for years with things like pears, apples, mountain ash, aronia, etc but I was recently told persimmon roots can’t take temps below 18* so I’m afraid the only way I’m going to be able to do this is with a pot in pot system. That or just give up on persimmons because I don’t want to have to build a special shelter for them & possibly heat it.
You can sink the pot into the ground over winter. Or, if there’s room in your garage, just slide the tree in there. They only need a modicum of protection.
I think 18 F is very conservative. Something like 5-10 F seems more reasonable. But a Z5B winter will usually get colder than that, so maybe the point is moot.
Do you have a garage? Maybe a barn or shed with a dirt or concrete slab floor? Without any insulation, the inside of such a structure should sustain a temperature somewhere between the outside air temperature (e.g., 0 F) and the ground temperature (e.g., 30 F). For example, I have an uninsulated detached garage that stays >20 F even when the outside air temperature is ~0 F. I routinely keep potted fig trees alive in there.
A shed with an air space underneath the floor doesn’t work because the ventilation sweeps away any warmth from the ground.
28 F is when fine roots are going to begin sustaining injury. I’ve always presumed this injury to be irrelevant. That’s where it starts, anyways.
From this Issue of a Hort paper you can understand now what happens to certain Genus and species observed under cold temperatures:
Your probably may be winds that dry and desiccate plant media where you lose all the water in the media and that’s when it’s game over. You gotta be able to penetrate water into a frozen solid “cube” of potting soil / and it isn’t possible unless you got it in a garage or shed or greenhouse, i.e. The water will run right around the sides of the rootball. Or, you’ll stand there in a cold garage for 5-minutes at a time to watch water slowly absorb.
The basic rule of anyone in the nursery business is to keep anything in containers 2-3 or 4 degrees warmer than 32 F.
Re ice: If the potting mix is damp and then it freezes into a solid mass, it doesn’t need to be watered. It’s already wet, and wind can’t penetrate the cube of ice. Yes, there can be some evaporation around the periphery. But the frozen block is by definition water. Think of it this way – If I put a big solid block of ice in a cold wind, will the inside of the block dry out? No.
Re temperature: The linked article states, “When plants are preconditioned for low temperature storage and the temperature remains uniformly low prior to exposure to cold-temperature, the roots will generally survive provided that the temperature does not go below the average killing temperature for the species.”
So in a normal northern U.S. winter, preceded by gradually cooling conditions in autumn, a persimmon that can survive +10 F when planted in the ground will survive +10 F when planted in a pot. The trick in Z5 is keeping the pot >10 F.
Thanks, I agree. I’ve never had the guts to set a pot outside alone. I’ve always covered it in mulch (apparently for no reason.) Or, I killed myself digging trench with a garden shovel and threw them. You have to have fence. All these things you learn the difficult way.
You gotta have some good mass of roots. A one gallon outta be enough I would tend to say.
John… thanks a lot. I’ll try a few plants next year.
I’ve overwinter native persimmons in pots for 2 years in 5b. I have both survive Temps down to -10F with no issue. This year will be 3rd winter, so we will see if they have survived.
“When plants are preconditioned for low temperature storage and
the temperature remains uniformly low prior to exposure to cold-temperature, the roots will generally survive provided that the temperature does not go below the average killing
temperature for the species.”
And
“To minimize root injury, plants should be stored
at a temperature at least 3-5°F above the average root-killing temperature.”
These seem to be at odds with each other. One talks about the root killing temp & the other is the species temp which appears from the chart to be much lower for the species than the root killing temps.
I know ground contact is important when over wintering potted plants and snow cover can make a big difference in keeping the pots much warmer than the air temp but as we all know, mother nature doesn’t always give us what we want. I’m glad Kellogg_Hill_Farms spoke up because we are in the same zone. Although I wish they had mentioned persimmon in that article just for curiosities sake. I guess I will have to try some on the ground exposed to the elements & hope I have as good of luck as I have with the other plants I mentioned. Then bury some pots just in case to be sure I have some make it. I may try some in a cold frame too.
I ordered a pound of 90 chromosome persimmon seed (500-700 seeds) so I should have plenty to experiment with.
@October1 – The article distinguishes between the temperature that kills tender, young roots and the temperature that kills all roots. The plant survives the former, not the latter.